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Intraoperative Assessment of Mitral Valve Area After Mitral Valve Repair: Comparison of Different Methods
Intraoperative Assessment of Mitral Valve Area After Mitral Valve Repair: Comparison of Different Methods Andrew Maslow, MD,* Anthony Gemignani, MD,* Arun Singh, MD,* Feroze Mahmood, MD,† and Athena Poppas, MD, FACC* Objective: In the present study, 3 different methods to measure the mitral valve area (MVA) after mitral valve repair (MVRep) were studied. Data obtained immediately after repair were compared with postoperative data. The objective was to determine the feasibility and correlation between intraoperative and postoperative MVA data. Design: A prospective study. Setting: A tertiary care medical center. Participants: Twenty-five elective adult surgical patients scheduled for MVRep. Methods: Echocardiographic data included MVAs obtained using the pressure half-time (PHT), 2-dimensional planimetry (2D-PLAN), and the continuity equation (CE). These data were obtained immediately after cardiopulmonary bypass and were compared with data obtained before hospital discharge (transthoracic echocardiogram 1) and 6 to 12 months after surgery (transthoracic echocardiogram
2). Intraoperative care was guided by hemodynamic goals designed to optimize cardiac function. Results: The data show good agreement and correlation between MVA obtained with PHT and 2D-PLAN within and between each time period. MVA data obtained with the CE in the postoperative period were lower than and did not correlate or agree as well with other MVA data. Conclusion: The MVA recorded immediately after valve repair, using PHT, correlated and agreed with MVA data obtained in the postoperative period. These results contrast with previously published data and could highlight the impact of hemodynamic function during the assessment of MVA. © 2011 Elsevier Inc. All rights reserved.
A
CCURATE INTRAOPERATIVE ASSESSMENT of the mitral valve (MV) after repair for mitral regurgitation (MR) is important to determine the success of the repair and whether or not rerepair is necessary. Inherent in the repair of the MV is an immediate reduction in the mitral valve area (MVA).1-3 A further reduction in the MVA is possible during follow-up,3-6 with significant stenosis being reported as early as 1 year after surgery.6 Intraoperative assessment of MV patency should be a part of the routine assessment after repair. Several studies have used pressure half-time (PHT) and 2-dimensional planimetry (2D-PLAN)1-5,7-9 to assess postoperative MVA during long-term follow-up; however, only 1 has studied intraoperative measurements.7 In this study, the intraoperative MVA by PHT underestimated that measured during follow-up and would have resulted in redo surgery in 14% of cases.7 Without a defined reference method to measure MVA after repair, echocardiographers have relied on transvalvular pressure gradients to assess valve patency.7 A previous case of post-repair stenosis highlighted issues with transvalvular gradients.10 In this case, measures of MVA suggested significant stenosis, whereas Doppler-derived gradients did not.10 Direct pressure measurements were elevated, which is consistent with mitral stenosis, prompting rerepair.10 The purpose of this investigation was to compare measures of the MVA obtained intraoperatively immediately after repair to those obtained early and late after surgery. The authors hypothesize that the MVA of the repaired valve, assessed intraoperatively, correlates and agrees with that measured during postoperative examinations.
cardiopulmonary bypass (CPB) hemodynamic management was performed according to divisional protocol to achieve the following prespecified goals: mean systemic blood pressure between 60 and 90 mmHg, central venous pressure ⱕ15 mmHg, pulmonary artery pressures within 25% (⫾) of pre-CPB values, and a cardiac index ⱖ2.5 L/min/m2. The heart rate was maintained between 80 and 100 beats/ min. Immediately after CPB, all patients were in an atrioventricular (AV) sequential rhythm (either sinus rhythm or a paced rhythm [DDD or DOO]) with an AV interval of ⱕ180 milliseconds. After separation from CPB and before chest closure, a comprehensive transesophageal echocardiographic examination (TEE) was performed by experienced echocardiographers. The assessment of the MV was performed in a similar fashion as described for the assessment of native valve stenosis11 and prosthetic valves.12 Measurements and calculations of the MVA were obtained using 2D-PLAN, PHT, and the continuity equation (CE). Planimetry was performed using the short axis en face transgastric view from the narrowest mitral orifice. From this view, the leaflet edges were identified and circumferentially traced with the leaflets at maximal excursion. During the echocardiographic examination, the CE was used, using the left ventricular outflow tract (LVOT) as a reference site, to calculate the MVA with the following equations: MVA ⫽ 0.785 (DiamLVIT ⫻ time velocity integralLVOT)/TVIMV. In the midesophageal long-axis view, the LVOT diameter was measured from the inner edge at the level of the aortic valve leaflet insertion.11,12 In the deep transgastric view, the pulse wave (PW) Doppler measure of the LVOT time velocity integral (TVI) was obtained from this same location. In 1 patient, who underwent aortic valve replacement, the main pulmonary artery was used as the reference site because the LVOT could not be well visualized and a diameter was not
METHODS
From the *Warren Alpert School of Medicine, Brown Medical School, Rhode Island Hospital, Providence, RI; and †Department of Anesthesiology, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA. Address reprint requests to Andrew Maslow, MD, 63 Prince Street, Needham, MA 02492. E-mail: [email protected] © 2011 Elsevier Inc. All rights reserved. 1053-0770/2502-0004$36.00/0 doi:10.1053/j.jvca.2010.11.022
After approval from the Internal Research Board, informed consent was obtained from 25 consecutive cardiac surgical patients aged 45 to 90 years scheduled for MV repair. All patients had severe mitral regurgitation without evidence of mitral stenosis before surgery. Intraoperative hemodynamic data were obtained from invasive arterial and pulmonary artery catheters. The use of vasoactive medications was left to the discretion of the attending anesthesiologist. Post–
KEY WORDS: pressure half-time, planimetry, mitral valve area, echocardiography, mitral valve repair
Journal of Cardiothoracic and Vascular Anesthesia, Vol 25, No 2 (April), 2011: pp 221-228
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measured easily. Mitral inflow TVI was recorded across the mitral leaflet tips using high-pulse-repetition frequency (HPRF). The PHT was measured using the deceleration slope of the early transmitral flow profile (E-wave) obtained using HPRF.12-14 For all patients, a distinct E-wave was discernible to allow measurement of the PHT. If the deceleration slope was bimodal, the second slower portion of the velocity profile was used. Using the PHT, the MVA was calculated as follows: MVA ⫽ 220/PHT. The mean and peak transvalvular gradients were obtained. The severity of MR was assessed by the vena contracta and spectral Doppler pulmonary venous flow profiles.15,16 An early postoperative transthoracic echocardiographic (TTE) (predischarge transthoracic echocardiography) examination was performed within a week of surgery, and a second follow-up TTE was performed 6 to 12 months after surgery. During all TTE examinations, patients were breathing spontaneously. These examinations were performed by sonographers and analyzed by an experienced echocardiographer (AP) who was blinded to the intraoperative examination. The MVA was obtained using 3 methods (ie, 2D PLAN, PHT, and the CE) during TTE examinations. Two-dimensional planimetry was obtained from the parasternal short-axis view using the parasternal long-axis view to help identify the leaflet tips. Doppler data were obtained from CW Doppler across the MV in the apical 4-chamber view with the cursor placed in the center of the inflow jet as identified by color Doppler.12,13 The diameter and PW Doppler data of the LVOT were obtained as per American Society of Echocardiography guidelines.12,13 For patients with atrial fibrillation, 5 measurements were obtained and averaged. Patient prosthesis mismatch (PPM) has been defined for prosthetic MVs as an indexed MVA (iMVA) ⱕ1.2 to 1.3 cm2/m2 or ⱕ1.25 cm2/m2.17-19 To assess an association between the MVA and a clinical correlate, MVA data were indexed per the patient’s body surface area, the latter being based on actual height and weight (ie, not ideal body weight), and compared with Doppler-measured pressure gradients. All measurements were obtained in triplicate and averaged. For patients with irregular rhythms, 5 measurements were obtained and averaged. For all patients, blood flow was aligned with the Doppler beam. Data were collected during brief periods of apnea in the intubated patient and during spontaneous respiration after extubation. Additional echocardiographic data included the left ventricular ejection fraction (LVEF) and the pulmonary artery systolic pressure (PASP) estimated from the peak velocity of the tricuspid regurgitant jet and an estimated central venous pressure.11,12 Central venous pressure was estimated by the size of the vena cava and its change during the respiratory cycle.20 Paired t tests were used to determine if significant differences existed between hemodynamic and echocardiographic data. To compare MVA and pressure gradient data obtained from different time periods, correlation and agreement statistics (Bland-Altman and bias analysis) were performed. Correlations were also assessed between the MVA data and pressure gradients. Given the number of comparisons made, using a Bonferroni correction, differences were considered statistically significant at p ⬍ 0.01. MVA data obtained at the same time period were compared using agreement statistics (bias analysis and Bland-Altman analysis). Interobserver variability was assessed for MVA data and analyzed. Analyses were performed using StatView (Statview Inc). RESULTS
Demographic and procedural data are listed in Table 1. During the immediate postoperative period, 2 patients did not receive any vasoactive medications, whereas 11 were receiving at least 2. During the intraoperative period, all patients were either in sinus rhythm or being synchronously paced via atrial and ventricular pacing wires. During the predischarge TTE, 6 patients had atrial fibrillation. During the follow-up TTE, 5
Table 1. Demographic and Procedural Data Age (y) Height (cm) Weight (kg) BSA (m2) Preoperative valvular function MR Aortic insufficiency Aortic stenosis Tricuspid regurgitation Mitral valve procedures Mitral ring annuloplasty Diameter (mm) 28 mm 30 mm 32 mm Anterior leaflet procedure Posterior leaflet procedure Bileaflet procedure Other surgical procedures Atrial septal defect closure Aortic valve replacement Coronary artery bypass Maze Tricuspid valve repair Vasoactive medications post-CPB None Number with 2⫹ medications Phosphodiesterase inhibitor Epinephrine Dopamine Dobutamine Norepinephrine Vasopressin Nitroglycerin
66.1 (⫾ 15.4) 170.1 (⫾11.5) 75.4 (⫾13.6) 1.86 (⫾0.2)
All 5 mild; 8 trace; 2 none 1 severe 3 severe; 6 moderate; 14 mild; 2 none
29.5 (⫾1.5) 9 11 5 4 16 5 1 1 2 4 9
2 11 12 8 5 2 9 1 4
NOTE. Unless specified, data are listed as absolute number. Vasoactive medications are those administered after CPB (ie, during the transesophageal echocardiography examination.)
patients had atrial fibrillation. For all patients, the heart rates were below 100 beats/min. Hemodynamic and echocardiographic data are listed in Tables 2 and 3. Data were recorded as mean ⫾ standard deviation (SD). Compared with the intraoperative period, the postoperative LVEF and the PASPs were significantly higher, whereas the heart rates were lower. Although the cardiac outputs, heart rates, and pulmonary artery pressures differed, the Doppler stroke volumes (SVs) were similar among the 3 different time periods. During the intraoperative TEE examination, there was less than 1⫹ MR in all cases. Two patients had 1 to 2⫹ MR during the predischarge TTE, and 4 had 1 to 2 ⫹ MR during the follow-up TTE. All others had ⬍1⫹ MR at the time of the echocardiographic examination. At all time periods, there was no significant TR or AI (⬍1⫹). There were no congenital lesions observed during these examinations. There were significant differences (p ⬍ 0.05) in the mean
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Table 2. Hemodynamic Data Obtained at Each Time Period
Post-CPB TEE TTE-1 TTE-2
LVEF
AI
HR
mBP
CVP
PASP
TDCO
SV TDCO
DCO
SV DCO
37.9 (8.0) 46.9 (12.7)‡§ 55.7 (9.8)‡
0.2 (0.3) 0.1 (0.3) 0.1 (0.4)
91.0 (7.6) 79.2 (9.0)‡ 73.8 (12.8)‡
69.2 (6.9) NA NA
9.6 (3.7) NA NA
28.0 (12.4) 37.9 (8.9)‡ 35.5 (8.4)†§
5.91 (1.46) NA NA
65.8 (19.5) NA NA
6.14 (1.57) 4.91 (1.34)* 4.85 (1.09)‡
68.2 (20.2) 62.7 (14.7) 64.9 (18.3)
NOTE. Data are listed as the mean ⫾ standard deviations. During the postoperative examinations (transthoracic echocardiogram 1 and transthoracic echocardiogram 2) blood pressure, central venous pressure and thermodilution cardiac outputs were not available (NA). Abbreviations: AI, aortic valve insufficiency; CVP, central venous pressure; DCO, Doppler cardiac output; HR, heart rate; mBP, mean systemic blood pressure; PASP, pulmonary artery systolic pressure; SV, stroke volume; TDCO, thermodilution cardiac output; TEE, transesophageal echocardiography; TTE, transthoracic echocardiography. *p ⬍ 0.05 versus post-CPB TEE. †p ⬍ 0.01 versus post-CPB TEE. ‡p ⬍ 0.001 versus post-CPB TEE. §p ⬍ 0.05 versus TTE-1.
MV TVI, which were greater during the predischarge TTE (29.4 ⫾ 6.0 cm) and the follow-up TTE (30.2 ⫾ 6.6 cm) compared with that recorded immediately after CPB (24.9 ⫾ 11.1 cm). Postoperative mean transvalvular gradients (predischarge TTE and follow-up TTE) were significantly higher than that obtained during the intraoperative examination (Table 3). There were 3 patients with an intraoperative post-repair transmitral mean gradient ⱖ6 (6, 6, and 7) and/or a peak gradient ⱖ10 (10, 12, and 14) mmHg. For these patients, the MVA was 2.7, 2.6, and 2.5 cm2, with respective cardiac outputs of 8.6, 9.0, and 9.3 L/min (heart rate of 90, 98, and 90, respectively). Otherwise, all mean gradients were ⬍6 mmHg. The PHT method was feasible in all patients studied. The 2D-PLAN was feasible in 19 of 25 (76%) of the intraoperative TEE cases and in 21 of 25 (84%) and 22 of 25 (88%) of predischarge TTE and follow-up TTE cases, respectively. The inability to perform planimetry was caused by poor visualization of all the leaflet edges in the same plane. The CE was feasible in 23 of 25 (92%) intraoperative cases, 22 of 25 (88%) during predischarge TTE, and all cases during follow-up TTE. Difficulties in performing the CE included difficulty measuring the diameter of the reference site (n ⫽ 2) and/or difficulty aligning the Doppler beam with blood flow (n ⫽ 3).
MVA data using the CE were significantly lower than data obtained using other methods at each time period. MVA data using the CE were lowest during the 2 postoperative examinations: a predischarge TTE and a TTE 6 to 12 months after surgery (Table 3). If mitral stenosis was considered to be an MVA ⬍1.8 cm2, then, based on PHT or 2D-PLAN, no patient had stenosis. Based on CE data, 1 (4%), 3 (14%), and 4 (16%) patients would have been considered to have mitral stenosis during the intraoperative and 2 postoperative examinations, respectively. At all time periods, there was good agreement between MVA data obtained with PHT and PLAN, whereas agreement between the CE data and other methods yielded larger mean biases (Tables 4-6). Correlation analyses yielded a range of results among the different examinations and time periods (Figs 1 and 2). Very good correlations (r ⱖ 0.80, p ⬍ 0.001) were found between the following: intraoperative PHT with intraopertive 2D-PLAN (r ⫽ 0.85, y ⫽ 0.47 ⫹ 0.86 x), intraoperative PHT with follow-up TTE PHT (r ⫽ 0.88; y ⫽ 0.38 ⫹ 0.86 x), and intraoperative 2D-PLAN and follow-up TTE PHT (r ⫽ 0.81, y ⫽ 0.45 ⫹ 0.84 x). Other comparisons showed lower r values (r ⬍ 0.80 and p ⬍ 0.05) but still significant correlations. These included comparisons between intraoperative PHT and postoperative 2D-PLAN
Table 3. Echocardiographic Data Including MVA Obtained by PHT, Planimetry, and the Doppler CE During the Intraoperative (Operating Room) TEE Examination Immediately After Separation From CPB, the TTE (TTE 1) Examination Before Hospital Discharge, and the Late TTE Examination 6 to 12 Months After Surgery (TTE 2)
Post-CPB TEE TTE 1 TTE 2
PHT
Planimetry
Doppler CE
Peak Gradient
Mean Gradient
2.96 (0.50)*ठ2.14-4.08 2.96 (0.68)ठ2.00-4.89 3.02 (0.49)*ठ2.26-4.30
2.99 (0.55)ठ1.90-3.80 2.91 (0.51)ठ1.83-3.90 3.07 (0.35)ठ2.51-3.80
2.71 (0.66)†‡$ 1.21-3.96 2.33 (0.56)*† 1.52-3.46 2.40 (0.70)*† 1.30-3.97
6.4 (2.3) 3.0-12.0 9.3 (2.6)储 3.8-12.0 8.5 (3.4)储¶ 3.5-18.0
3.3 (1.2) 1.0-1.6 4.1 (1.2) 2.1-7.0 3.5 (1.5) 1.0-7.0
NOTE. All data are presented as the mean (standard deviation); CE, reference flow using Doppler. *p ⬍ 0.01 versus the post-CPB transesophageal echocardiographic CE Doppler. †p ⬍ 0.05 versus the post-CPB transesophageal echocardiographic CE thermodilution. ‡p ⬍ 0.01 versus the predischarge TTE CE. §p ⬍ 0.01 versus the late transesophageal echocardiographic CE. 储p ⬍ 0.01 versus the post-CPB gradient. ¶p ⬍ 0.001 versus the TTE 1 gradient.
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Table 4. Agreement Between Methods of MVA Measurement Within Each Study Period Operating Room Post-CPB
Mean MVA Bias
TTE 1
TTE 2
PHT and PLAN
PHT and CE
PLAN and CE
PHT and PLAN
PHT and CE
PLAN and CE
PHT and PLAN
PHT and CE
PLAN and CE
2.96 (0.53) ⫺0.04 (0.29)
2.84 (0.54) 0.26 (0.51)
2.89 (0.50) 0.16 (0.43)
2.94 (0.58) 0.07 (0.51)
2.63 (0.47) 0.59 (0.86)
2.57 (0.48) 0.56 (0.56)
3.09 (0.39) 0.03 (0.37)
2.72 (0.52) 0.59 (0.66)
2.80 (0.52) 0.58 (0.61)
NOTE. Data include mean bias and standard deviations. Data are presented as centimeters squared. Abbreviations: TTE 1, predischarge transthoracic echocardiographic examination; TTE 2, 6- to 12-month transthoracic echocardiographic examination.
that were fair (predischarge TTE, r ⫽ 0.72; follow-up TTE, r ⫽ 0.65). The correlation between intraoperative 2D-PLAN and postoperative 2D-PLAN also was fair (predischarge TTE, r ⫽ 0.76; follow-up TTE, r ⫽ 0.65). Correlation results involving the CE varied from r ⫽ ⫺0.19 to 0.65, with the majority being less than 0.6. The lower correlations and agreement between CE and other MVA data were not improved by omitting patients with postoperative atrial fibrillation and/or MR ⱖ2⫹. Using the different measures of MVA, the incidence of PPM based on the intraoperative examination was 12.5%, 16.7%, and 27.3% for PHT, planimetry, and CE, respectively. During the predischarge TTE, the incidence was 13.0%, 5.3%, and 52.6% for PHT, planimetry, and CE, respectively. During the late TTE, the incidence was 9.1%, 5.3%, and 59% for PHT, planimetry, and CE, respectively. There were no significant correlations between MVA and transvalvular gradients at any of the time periods. When analyzing iMVA several moderate (r ⫽ ⫺0.54 to ⫺0.69) but statistically significant (p ⬍ 0.01) correlations between intraoperative iMVA (PHT and planimetry, respectively) and the mean intraoperative transvalvular gradient were found. Other correlations between MVA data and pressure gradients failed to reach significance. Interobserver variability was assessed using agreement statistics between 2 echocardiographers. During the intraoperative examination, the mean biases (⫾SD) for 2D-PLAN (⫺0.29 cm2 ⫾ 0.45), CE MVA (0.31 cm2 ⫾ 0.45), and PHT (0.14 cm2 ⫾ 0.35) were found. Compared with the mean MVA data for each method, these corresponded to a 10% (2DPLAN), 11% (CE MVA), and a 5% (PHT) difference between the 2 examiners. During the follow-up TTE examination, the mean biases (⫾SD) for 2D-PLAN (⫺0.58 cm2 ⫾ 0.95), CE MVA (⫺0.23 cm2 ⫾ 0.50), and PHT (0.17 cm2 ⫾ 0.47) were recorded. Compared with the mean MVA data for each method, these corresponded to an 18% (2D-PLAN), 10% (CE-MVA), and a 6% (PHT) difference between the 2 examiners.
DISCUSSION
This study showed that the intraoperative measurement of MVA, using PHT and 2D-PLAN, had good agreement and correlation with respective data obtained in the postoperative time periods. By contrast, MVAs calculated by the CE were lower than and did not correlate as well with MVA data obtained using PHT or 2D-PLAN. Overall, the PHT technique was more feasible than other methods, whereas 2D PLAN was the least. The intraoperative TEE assessment of the repaired MV is important to determine surgical success and guide further management.6,7,10 Although the assessment of post-repair regurgitation mirrors that used with native valves, the evaluation of valve patency has not been established. Level 1 recommendations for assessing native valve patency include transvalvular pressure gradients, 2D-PLAN, and PHT; however, after MV procedures (repair or replacement), these techniques are not well studied and may be affected by physiologic and anatomic changes.11,12,21 The present study is the second intraoperative study to assess MVA after repair and the first to compare the different methods of assessment. In the one other intraoperative study, the mean intraoperative MVA, assessed by TEE using PHT underestimated the mean postoperative TTE value (2.1 ⫾ 0.5 cm2 v 2.7 ⫾ 1.0 cm2) performed (PHT) on average 10 weeks later.7 For 5 patients, the intraoperative value would have resulted in revision of the repair.7 As a result, Poh et al7 concluded that intraoperative PHT was not an accurate reflection of valve patency and suggested that a mean transvalvular pressure gradient ⱖ10 mmHg may be the better measure of post-repair stenosis. The present authors recently reported a case in which postrepair stenosis was suspected based on 2D-PLAN and PHT but not by the Doppler pressure gradient (peak ⫽ 6 mmHg).10 Direct measurement of the pressure gradient was elevated significantly (16 mmHg), confirming-post repair stenosis and showing the limitations of a Doppler-assessed gradient after
Table 5. Agreement Between Methods of the MVA Measurement for Each Method and Between Time Periods PHT
Planimetry
CE
OR and TTE 1 OR and TTE 2 TTE 1 and TTE 2 OR and TTE 1 OR and TTE 2 TTE 1 and TTE 2 OR and TTE 1 OR and TTE 2 TTE 1 and TTE 2
Mean MVA Bias
2.98 (0.53 0.03 (0.53)
3.01 (0.47) ⫺0.03 (0.24)
3.03 (0.55) ⫺0.05 (0.48)
3.00 (0.48) 0.19 (0.36)
3.12 (0.36) 0.12 (0.35)
3.08 (0.36) ⫺0.11 (0.31)
2.50 (0.53 0.32 (0.67)
2.52 (0.65) 0.32 (0.48)
2.31 (0.48) ⫺0.06 (0.86)
NOTE. Data include mean bias and standard deviations. Data are presented as centimeters squared. Abbreviations: OR, operating room; TTE 1, predischarge transthoracic echocardiographic examination; TTE 2, 6- to 12-month transthoracic echocardiographic examination.
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Table 6. Agreement Between the Intraoperative MVA Measurement Obtained With the PHT and 2D-PLAN Obtained During the Early (TTE 1) and Late (TTE 2) Echocardiographic Follow-up
Mean MVA Bias
OR PHT and TTE 1 PLAN
OR PHT and TTE 2 PLAN
2.98 (0.46) 0.15 (0.37)
3.07 (0.39) ⫺0.01 (0.37)
NOTE. Data are presented as centimeters squared. Abbreviations: TTE 1, predischarge transthoracic echocardiographic examination; TTE 2, 6- to 12-month transthoracic echocardiographic examination.
repair.10-12 Pressure gradients offer a simple estimation of valve patency and are clinically important because they represent the degree of pressure load to the atrium and pulmonary vasculature. Previously defined parameters for mitral stenosis (MVA ⱕ1.8 cm2) include mean and peak gradients ⱖ6 and 12 mmHg, respectively.11,22 Gradients, however, are dependent on other variables besides valve area, including blood flow, heart rate, net AV compliance, and the angle of interrogation between the ultrasound beam and blood flow. The latter may be an important issue for the repaired valve.10-12,23 In the present study, there were 3 patients with a mean intraoperative gradient ⱖ6 mmHg, and none was associated with mitral stenosis (MS) by any measure of MVA. In addition, no significant correlation was found between intraoperative transvalvular pressure gradients and MVA data. Therefore, echocardiographers should not rely solely on the pressure gradients to assess valve patency after repair. The PHT is easy to obtain, has acceptably low inter- and intraobserver variability, and has been shown to be accurate over a wide range of MVAs.11,12,24 Compared with pressure gradients, the PHT is less affected by changes in heart rate and ultrasound interrogation angles, the latter remaining accurate with angles up to 40°.11,13 It is, however, affected by changes in net AV compliance, pressure gradients, and cardiac outputs.12,13,24,25-29 For patients with MS, acute changes in these
Fig 1. A regression figure of the MVA data measured using the PHT obtained immediately after MV repair and during the later follow-up (follow-up transthoracic echocardiogram). There was a good correlation between the 2 datasets (r ⴝ 0.88, y ⴝ 0.36 ⴙ 0.86 x, p < 0.0001).
variables, as seen experimentally24 and after percutaneous valvuloplasty,26-28 affect the accuracy of the PHT to calculate the MVA. The relief of MS acutely changes left atrial (LA) function, whereas MV surgery for MR acutely increases left ventricular afterload and dysfunction, which also may affect LA function.30,31 Patients with pure MR (ie, no preoperative stenosis) may experience a minimal change in net AV compliance after MV surgery.30,31 If this is the case, then the PHT will vary with the MVA as described previously (MVA ⫽ 220/PHT).24 The limitations of PHT, as described in patients with MS, may not apply to patients undergoing valve surgery for MR.7,12,26-29 The present study does not necessarily contradict the findings by Poh et al7 but, instead, highlights the importance of reporting and optimizing hemodynamic function during the assessment of MVA after repair.4,9 Compared with the study by Poh et al in which hemodynamic data were limited to heart rate and blood pressure, the present study used more invasive monitoring and a more aggressive hemodynamic management protocol immediately after MV repair. The effect of hemodynamic function on MVA is more pronounced for valves with greater leaflet mobility and potential for annular expansion.13,14,32-37 In 2 studies, one using 2D-PLAN and another using PHT, the MVA of the repaired valve increased approximately 30% during exercise and correlated with increases in SV and heart rate.4,9 Although these reports involved Alfieri repairs, the principle relating hemodynamics to MV function should be similar, or perhaps greater, with other repair techniques that do not restrict leaflet motion. The repaired valve has reserve function, and the assessment of MVA should be performed when hemodynamic function is optimized. Two-dimensional planimetry is a direct measurement of MVA and was shown to best correlate with the area of explanted rheumatic stenotic valves.38 Therefore, 2D-PLAN is considered the reference to compare other measures of MVA.11,22 However, for nonplanar or “dome-shaped” valves, its accuracy and feasibility are reduced for both TTE (feasibility 89%) and TEE (feasibility 69%) because of difficulties in imaging all leaflet edges in the same plane.21,39-42 This is also an
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Fig 2. A regression figure of the MVA data measured using the PHT and 2D-PLAN. The former was obtained during the intraoperative examination, whereas the latter was obtained during the later follow-up (follow-up transthoracic echocardiogram). There was a good correlation between the 2 datasets (r ⴝ 0.85, y ⴝ 0.47 ⴙ 0.86 x, p < 0.0001).
issue after MV repair.21 Three-dimensional imaging with offline planimetry (3D-PLAN) may obviate the problems with nonplanar structures by identifying the narrowest orifice21,23,41; however, its intraoperative online application has not been reported. A TTE study after MV repair noted that 3D-PLAN correlated and agreed with PHT more than with 2D-PLAN because of the difficulty in imaging the leaflet edges during 2-dimensional interrogation.21 This is the first study to examine MVA assessment using the CE after repair. As could be expected, MVA data measured by the CE was lower than MVA data from PHT and 2D-PLAN. This difference is the coefficient of contraction.11,43,44 The CE assesses flow at the vena contracta and calculates the effective valve area, which could be as low as 65% to 85% of the anatomic MVA, as measured by the Gorlin equation.11,43,44 Although a lower MVA by the CE could have been anticipated at all time points, it does not explain why intraoperative CE MVAs were greater than postoperative CE MVAs or why the correlation between CE MVA and other MVA data was low. Omitting patients with ⱖ2⫹ MR during the postoperative TTE did not improve the correlation. Measurement errors or inaccuracies could help to explain the CE data. Although Doppler-measured velocity data obtained with either HPRF or CW Doppler have been reported to be similar,45 other data have not.46 The latter study reported poor correlation at lower velocities and underestimation by HPRF at higher velocities.46 A lower intraoperative MV TVI obtained with HPRF would result in a higher MVA compared with the respective data obtained with CW Doppler. Although this may help to explain why intraoperative CE MVA data were higher than postoperative, it does not explain the lack of correlation between CE data (intraoperative or postoperative) and other MVA data obtained with PHT or 2D-PLAN. The authors speculate that the results were likely caused by measurement errors, reflecting the multiple variables needed to perform the CE.11,47 Although the authors do not discount the possibility that the CE might be a useful measure of MVA after repair, they do caution against its use based on the data presented here.
In the absence of a gold standard, it is still unknown as to which measure of MVA is accurate or clinically important. Previous reports show a good correlation among different echocardiographic methods, including PHT, when the MVA is ⬍2.0 cm2 under varying hemodynamic conditions.32,34 A postoperative study of patients after MV repair found 3D-PLAN to agree with 2D-PLAN and PHT.21,41 If intraoperative and postoperative data agree, as shown in the present study, and 3D-PLAN is considered a reference method, then it might be speculated that intraoperative MVA assessment of the repaired valve is feasible and accurate. However, an intraoperative investigation comparing 3D-PLAN with 2D-PLAN and PHT has not been performed to confirm this statement. Without a clinical correlate, it is difficult to know what method of measurement is important and/or below what MVA is considered problematic after valve repair. For the native valve, mitral stenosis has been defined as ⬍1.8 cm2 and associated with increased transvalvular gradients, left atrial dysfunction and arrhythmias, pulmonary hypertension, and heart failure.11 Although it is uncommon to record a prosthetic or post-repair MVA ⬍1.8 cm2, investigators have described PPM for the prosthetic valve as an iMVA of ⬍1.2 to 1.3 cm2/m2.17-19 In these studies, PPM was associated with increased morbidity and mortality.17-19 Using a similar definition, PPM, in the present study, occurred between 5% and 12% for data obtained using PHT and 2D-PLAN and 25% to 60% using CE data. A significant correlation was found between transvalvular gradients and the iMVA data obtained using PHT and 2D-PLAN but not with CE data. Although the transvalvular gradient represents the pressure load on the LA and pulmonary veins, the absence of a long-term follow-up makes any conclusion regarding the importance of PPM on the repaired valve premature. Limitations Measures of net AV compliance were not performed in the present study. Although some direct and indirect measures of heart function (ie, PASP, SV, and LVEF) were recorded, it was
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not possible to make assumptions regarding chamber compliance. The authors cannot eliminate a potential bias during a given time period because the measurements were obtained by the same echocardiographer. Good agreement between the measures of MVA during each time period could have been affected by this bias. However, the intraoperative and postoperative examinations were assessed by different echocardiographers, each being blinded to the respective data; therefore, the correlations between intraoperative and postoperative MVA data should not be affected. The measurement of transmitral flow velocities between time points should have been better standardized. The use of HPRF during the intraoperative period could explain the differences between intraoperative and postoperative CE data, and to a lesser extent, the correlation with other methods.45 Theoretically, the HPRF allows measurement of higher-velocity flows (compared with PW Doppler) with less range ambiguity than CW Doppler. Although previously published data showed accurate assessment of peak velocity with HPRF when compared with CW,46 others noted that HPRF underestimates peak velocities compared with CW Doppler, particularly with highervelocity flows.45
Finally, the interobserver variability was greater for 2DPLAN and the CE than for the PHT. This likely reflects the simplicity of the PHT method compared with PLAN and the CE and has been shown by others. Although the variability among the PHT data was lowest, the standard deviation was high enough such that 2 different examiners may conclude different levels of valve function. As guidelines suggest for native valve stenosis, a comprehensive evaluation of valve patency after repair should synthesize multiple methods and measurements. CONCLUSION
The present study showed that the MVA, assessed by PHT or 2D-PLAN, recorded intraoperatively after valve repair agreed and correlated with MVA data obtained with similar methods in the early and late postoperative period. The discrepancy with the one other intraoperative study highlights the importance of optimizing hemodynamics during assessment of MVA. Although the present study found similar MVA when assessed at different time periods, the authors could not conclude whether PHT or PLAN should be used as a reference or gold standard. Future study should compare intraoperative echocardiographic measurements with 3D-PLAN.
REFERENCES 1. Unger-Graeber B, Lee RT, Sutton MS, et al: Doppler echocardiographic comparison of the Carpentier and Duran annuloplasty rings versus no ring after mitral valve repair for mitral regurgitation. Am J Cardiol 67:517-519, 1991 2. Sakamoto Y, Hashimoto K, Okuyama H, et al: Long-term assessment of mitral valve reconstruction with resection of the leaflets: Triangular and quadrangular resection. Ann Thorac Surg 79:475-479, 2005 3. Kobayashi Y, Nagata S, Ohmori F, et al: Mitral valve dysfunction resulting from thickening and stiffening of artificial mitral valve chordae. Circulation 94:II129-II132, 1996 4. Umana JP, Salehizadeh B, DeRose JJ Jr, et al: “Bow-tie” mitral valve repair: An adjuvant technique for ischemic mitral regurgitation. Ann Thorac Surg 66:1640-1646, 1998 5. Ibrahim MF, David TE: Mitral stenosis after mitral valve repair for non-rheumatic mitral regurgitation. Ann Thorac Surg 73:34-36, 2002 6. Brinster DR, Unic D, D’Ambra M, et al: Midterm results of the edge-to-edge technique for complex mitral valve repair. Ann Thorac Surg 81:1612-1617, 2006 7. Poh KK, Hong EC, Yang H, et al: Transesophageal echocardiography during mitral valve repair underestimates mitral valve area by pressure half-time calculation. Int J Cardiol 108:177-180, 2006 8. Camilleri LF, Miguel B, Bailly P, et al: Flexible posterior mitral annuloplasty: Five-year clinical and Doppler echocardiographic results. Ann Thorac Surg 66:1692-1697, 1998 9. Agricola E, Maisano F, Oppizzi M, et al: Mitral valve reserve in double-orifice technique: An exercise echocardiographic study. J Heart Valve Dis 11:637-643, 2002 10. Maslow AD, Singh A, Mahmood F, et al: Intraoperative assessment of mitral valve area after mitral valve repair for regurgitant valves. J Cardiothorac Vasc Anesth 25:221-228, 2011 11. Baumgartner H, Jung J, Bermejo J, et al: Echocardiographic assessment of valve stenosis: EAE/ASE recommendation for clinical practice. J Am Soc Echocardiogr 22:1-23, 2009
12. Zoghbi WA, Chambers JB, Dumesnil JG, et al: Recommendations for evaluation of prosthetic valves with echocardiography and Doppler ultrasound. J Am Soc Echocardiogr 22:975-1014, 2009 13. Hatle L, Angelsen B, Tromsdal A: Noninvasive assessment of atrioventricular pressure half-time by Doppler ultrasound. Circulation 60:1096-1104, 1979 14. Hatle L, Brubakk A, Tromsdal A, et al: Noninvasive assessment of pressure drop in mitral stenosis by Doppler ultrasound. Br Heart J 40:131-140, 1978 15. Lim E, Ali ZA, Barlow CW, et al: Determinants and assessment of regurgitation after mitral valve repair. J Thoracic Cardiovasc Surg 124:911-917, 2002 16. Zoghbi WA, Enriquez-Sarano M, Foster E, et al: American Society of Echocardiography. Recommendations for evaluation of the severity of native valvular regurgitation with two-dimensional and Doppler echocardiography. J Am Soc Echocardiogr 16:777802:2003 17. Lam BK, Chan V, Hendry P, et al: The impact of patientprosthesis mismatch on late outcomes after mitral valve replacement. J Thorac Cardiovasc Surg 133:1464-1473, 2007 18. Li M, Dumesnil JG, Mathieu P, et al: Impact on valve prosthesis-mismatch on pulmonary arterial pressure after mitral valve replacement. J Am Coll Cardiol 45:1034-1040, 2005 19. Aziz A, Lawton JS, Maniar HS, et al: Factors affecting survival after mitral valve replacement in patients with patients prosthesis mismatch. Ann Thorac Surg 90:1202-1211, 2010 20. Ommen SR, Nishimura RA, Hurrell DG, et al: Assessment of right atrial pressure with 2-dimensional and Doppler echocardiography: A simultaneous catheterization and echocardiographic study. Mayo Clin Proc 75:24-29, 2000 21. Hoole SP, Liew TV, Boyd J et al: Transthoracic real-time three-dimensional echocardiography offers additional value in the assessment of mitral valve morphology and area following mitral valve repair. Europ J Echocardiogr 9:625-630, 2008
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22. Bonow RO, Carabello BA, Chatterjee K, et al: ACC/AHA 2006 guidelines for the management of patients with valvular heart disease. J Am Coll Cardiol 48:e1-e148, 2006 23. Green GR, Dagum P, Glasson JR, et al: Restricted posterior leaflet motion after mitral ring annuloplasty. Ann Thorac Surg 68:21002106, 1999 24. Thomas JD, Weyman AE: Doppler mitral pressure half-time: A clinical tool in search of theoretical justification. J Am Coll Cardiol 10:923-929, 1987 25. Stoddard MF, Prince CR, Tuman WL, et al: Angle of incidence does not affect accuracy of mitral stenosis area calculation by pressure half-time: Application to Doppler transesophageal echocardiography. Am Heart J 127:1562-1572, 1994 26. Zamorano J, Perez de Isla L, Sugeng L, et al: Non-invasive assessment of mitral valve area during percutaneous balloon mitral valvuloplasty: Role of real-time 3D echocardiography. Eur Heart J 25:2086-2091, 2004 27. Sunil Roy TN, Krishnan MN, Koshy C, et al: Comparison of proximal isovelocity surface area method and pressure half time method for evaluation of mitral valve area in patients undergoing balloon mitral valvotomy. Echocardiography 22:707-712, 2005 28. Thomas JD, Wilkins GT, Choong CY, et al: Inaccuracy of mitral pressure half-time immediately after percutaneous mitral valvotomy. Dependence on transmitral gradient and left atrial and ventricular compliance. Circulation 78:980-993, 1988 29. Kim HK, Kim YJ, Chang SA, et al: Impact of cardiac rhythm on mitral valve area calculated by the pressure half time method in patients with moderate or severe mitral stenosis. J Am Soc Echocardiogr 22:42-47, 2009 30. Zile MR, Gaasch WH, Levine HJ: Left ventricular stress dimension-shortening relation before and after correction of chronic aortic and mitral regurgitation. Am J Cardiol 56:99-105, 1985 31. Wong CYH, Spotnitz HM: Systolic and diastolic properties of the human left ventricle during valve replacement for chornic mitral regurgitation. Am J Cardiol 47:40-50, 1981 32. Loperfido F, Laurenzi F, Gimigliano F, et al: A comparison of the assessment of mitral valve area by continuous wave Doppler and by cross sectional echocardiography. Br Heart J 57:348-355, 1987 33. Libanoff AJ, Rodbard S: Atrioventricular pressure half-time. Measure of mitral valve orifice area. Circulation 38:144-150, 1968 34. Braverman AC, Thomas JD, Lee RT: Doppler echocardiographic estimation of mitral valve area during changing hemodynamic conditions. Am J Cardiol 68:1485-1490, 2001 35. Voelker W, Karsch KR: Exercise Doppler echocardiography in conjunction with right heart catheterization for the assessment of mitral stenosis. Int J Sports Med 17:S191-S195, 1996
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36. Voelker W, Berner A, Regele B, et al: Effect of exercise on valvular resistance in patients with mitral stenosis. J Am Coll Cardiol 22:777-782, 1993 37. Dahan M, Paillole C, Martin D, et al: Determinants of stroke volume response to exercise in patients with mitral stenosis: A Doppler echocardiographic study. J Am Coll Cardiol 21:384-389, 1993 38. Faletra F, Pezzano A Jr, Fusco R, et al: Measurement of mitral valve area in mitral stenosis: Four echocardiographic methods compared with direct measurement of anatomic orifices. J Am Coll Cardiol 28:1190-1197, 1996 39. Stoddard MF, Prince CR, Ammash NM, et al: Two-dimensional transesophageal echocardiograhic determination of mitral valve area in adults with mitral stenosis. Am Heart J 127:1348-1353, 1994 40. Binder TM, Rosenhek R, Porenta G, et al: Improved assessment of mitral valve stenosis by volumetric real-time three-dimensional echocardiography. J Am Coll Cardiol 36:1355-1361, 2000 41. Chen Q, Nosiir YM, Vietter WB, et al: Accurate assessment of mitral valve area in patients with mitral stenosis by three-dimensional echocardiography. J Am Soc Echocardiogr 10:133-140, 1997 42. Sugeng L, Weinert L, Lammertin G, et al: Accuracy of mitral valve area measurements using transthoracic rapid freehand 3-dimensional scanning: Comparison with noninvasive and invasive methods. J Am Soc Echocardiogr 16:1292-1300, 2003 43. Gilon D, Cape EG, Handschumacher MD, et al: Effect of three-dimensional valve shape on the hemodynamics of aortic stenosis: Three-dimensional echocardiographic stereolithography and patient studies. J Am Coll Cardiol 40:1479-1486, 2002 44. Bitar JN, Lechin ME, Salazar G, et al: Doppler echocardiographic assessment with the continuity equation of St Jude Medical mechanical prostheses in the mitral valve position. Am J Cardiol 76:287-293, 1995 45. Snider AR, Stevenson JG, French JW, et al: Comparison of high pulse repetition frequency and continuous wave Doppler echocardiography for velocity measurement and gradient prediction in children with valvular and congenital heart disease. J Am Coll Cardiol 7:873879, 1986 46. Stewart WJ, Galvin KA, Gilliam LD, et al: Comparison of high pulse repetition frequency and continuous wave Doppler echocardiography in assessment of high flow velocity in patients with valvular stenosis and regurgitation. J Am Coll Cardiol 6:565-571, 1985 47. Bednarz JE, Krauss D, Long RM: An echocardiographic approach to the assessment of aortic stenosis. J Am Soc Echocardiog 9:286-294, 1996
2). Intraoperative care was guided by hemodynamic goals designed to optimize cardiac function. Results: The data show good agreement and correlation between MVA obtained with PHT and 2D-PLAN within and between each time period. MVA data obtained with the CE in the postoperative period were lower than and did not correlate or agree as well with other MVA data. Conclusion: The MVA recorded immediately after valve repair, using PHT, correlated and agreed with MVA data obtained in the postoperative period. These results contrast with previously published data and could highlight the impact of hemodynamic function during the assessment of MVA. © 2011 Elsevier Inc. All rights reserved.
A
CCURATE INTRAOPERATIVE ASSESSMENT of the mitral valve (MV) after repair for mitral regurgitation (MR) is important to determine the success of the repair and whether or not rerepair is necessary. Inherent in the repair of the MV is an immediate reduction in the mitral valve area (MVA).1-3 A further reduction in the MVA is possible during follow-up,3-6 with significant stenosis being reported as early as 1 year after surgery.6 Intraoperative assessment of MV patency should be a part of the routine assessment after repair. Several studies have used pressure half-time (PHT) and 2-dimensional planimetry (2D-PLAN)1-5,7-9 to assess postoperative MVA during long-term follow-up; however, only 1 has studied intraoperative measurements.7 In this study, the intraoperative MVA by PHT underestimated that measured during follow-up and would have resulted in redo surgery in 14% of cases.7 Without a defined reference method to measure MVA after repair, echocardiographers have relied on transvalvular pressure gradients to assess valve patency.7 A previous case of post-repair stenosis highlighted issues with transvalvular gradients.10 In this case, measures of MVA suggested significant stenosis, whereas Doppler-derived gradients did not.10 Direct pressure measurements were elevated, which is consistent with mitral stenosis, prompting rerepair.10 The purpose of this investigation was to compare measures of the MVA obtained intraoperatively immediately after repair to those obtained early and late after surgery. The authors hypothesize that the MVA of the repaired valve, assessed intraoperatively, correlates and agrees with that measured during postoperative examinations.
cardiopulmonary bypass (CPB) hemodynamic management was performed according to divisional protocol to achieve the following prespecified goals: mean systemic blood pressure between 60 and 90 mmHg, central venous pressure ⱕ15 mmHg, pulmonary artery pressures within 25% (⫾) of pre-CPB values, and a cardiac index ⱖ2.5 L/min/m2. The heart rate was maintained between 80 and 100 beats/ min. Immediately after CPB, all patients were in an atrioventricular (AV) sequential rhythm (either sinus rhythm or a paced rhythm [DDD or DOO]) with an AV interval of ⱕ180 milliseconds. After separation from CPB and before chest closure, a comprehensive transesophageal echocardiographic examination (TEE) was performed by experienced echocardiographers. The assessment of the MV was performed in a similar fashion as described for the assessment of native valve stenosis11 and prosthetic valves.12 Measurements and calculations of the MVA were obtained using 2D-PLAN, PHT, and the continuity equation (CE). Planimetry was performed using the short axis en face transgastric view from the narrowest mitral orifice. From this view, the leaflet edges were identified and circumferentially traced with the leaflets at maximal excursion. During the echocardiographic examination, the CE was used, using the left ventricular outflow tract (LVOT) as a reference site, to calculate the MVA with the following equations: MVA ⫽ 0.785 (DiamLVIT ⫻ time velocity integralLVOT)/TVIMV. In the midesophageal long-axis view, the LVOT diameter was measured from the inner edge at the level of the aortic valve leaflet insertion.11,12 In the deep transgastric view, the pulse wave (PW) Doppler measure of the LVOT time velocity integral (TVI) was obtained from this same location. In 1 patient, who underwent aortic valve replacement, the main pulmonary artery was used as the reference site because the LVOT could not be well visualized and a diameter was not
METHODS
From the *Warren Alpert School of Medicine, Brown Medical School, Rhode Island Hospital, Providence, RI; and †Department of Anesthesiology, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA. Address reprint requests to Andrew Maslow, MD, 63 Prince Street, Needham, MA 02492. E-mail: [email protected] © 2011 Elsevier Inc. All rights reserved. 1053-0770/2502-0004$36.00/0 doi:10.1053/j.jvca.2010.11.022
After approval from the Internal Research Board, informed consent was obtained from 25 consecutive cardiac surgical patients aged 45 to 90 years scheduled for MV repair. All patients had severe mitral regurgitation without evidence of mitral stenosis before surgery. Intraoperative hemodynamic data were obtained from invasive arterial and pulmonary artery catheters. The use of vasoactive medications was left to the discretion of the attending anesthesiologist. Post–
KEY WORDS: pressure half-time, planimetry, mitral valve area, echocardiography, mitral valve repair
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measured easily. Mitral inflow TVI was recorded across the mitral leaflet tips using high-pulse-repetition frequency (HPRF). The PHT was measured using the deceleration slope of the early transmitral flow profile (E-wave) obtained using HPRF.12-14 For all patients, a distinct E-wave was discernible to allow measurement of the PHT. If the deceleration slope was bimodal, the second slower portion of the velocity profile was used. Using the PHT, the MVA was calculated as follows: MVA ⫽ 220/PHT. The mean and peak transvalvular gradients were obtained. The severity of MR was assessed by the vena contracta and spectral Doppler pulmonary venous flow profiles.15,16 An early postoperative transthoracic echocardiographic (TTE) (predischarge transthoracic echocardiography) examination was performed within a week of surgery, and a second follow-up TTE was performed 6 to 12 months after surgery. During all TTE examinations, patients were breathing spontaneously. These examinations were performed by sonographers and analyzed by an experienced echocardiographer (AP) who was blinded to the intraoperative examination. The MVA was obtained using 3 methods (ie, 2D PLAN, PHT, and the CE) during TTE examinations. Two-dimensional planimetry was obtained from the parasternal short-axis view using the parasternal long-axis view to help identify the leaflet tips. Doppler data were obtained from CW Doppler across the MV in the apical 4-chamber view with the cursor placed in the center of the inflow jet as identified by color Doppler.12,13 The diameter and PW Doppler data of the LVOT were obtained as per American Society of Echocardiography guidelines.12,13 For patients with atrial fibrillation, 5 measurements were obtained and averaged. Patient prosthesis mismatch (PPM) has been defined for prosthetic MVs as an indexed MVA (iMVA) ⱕ1.2 to 1.3 cm2/m2 or ⱕ1.25 cm2/m2.17-19 To assess an association between the MVA and a clinical correlate, MVA data were indexed per the patient’s body surface area, the latter being based on actual height and weight (ie, not ideal body weight), and compared with Doppler-measured pressure gradients. All measurements were obtained in triplicate and averaged. For patients with irregular rhythms, 5 measurements were obtained and averaged. For all patients, blood flow was aligned with the Doppler beam. Data were collected during brief periods of apnea in the intubated patient and during spontaneous respiration after extubation. Additional echocardiographic data included the left ventricular ejection fraction (LVEF) and the pulmonary artery systolic pressure (PASP) estimated from the peak velocity of the tricuspid regurgitant jet and an estimated central venous pressure.11,12 Central venous pressure was estimated by the size of the vena cava and its change during the respiratory cycle.20 Paired t tests were used to determine if significant differences existed between hemodynamic and echocardiographic data. To compare MVA and pressure gradient data obtained from different time periods, correlation and agreement statistics (Bland-Altman and bias analysis) were performed. Correlations were also assessed between the MVA data and pressure gradients. Given the number of comparisons made, using a Bonferroni correction, differences were considered statistically significant at p ⬍ 0.01. MVA data obtained at the same time period were compared using agreement statistics (bias analysis and Bland-Altman analysis). Interobserver variability was assessed for MVA data and analyzed. Analyses were performed using StatView (Statview Inc). RESULTS
Demographic and procedural data are listed in Table 1. During the immediate postoperative period, 2 patients did not receive any vasoactive medications, whereas 11 were receiving at least 2. During the intraoperative period, all patients were either in sinus rhythm or being synchronously paced via atrial and ventricular pacing wires. During the predischarge TTE, 6 patients had atrial fibrillation. During the follow-up TTE, 5
Table 1. Demographic and Procedural Data Age (y) Height (cm) Weight (kg) BSA (m2) Preoperative valvular function MR Aortic insufficiency Aortic stenosis Tricuspid regurgitation Mitral valve procedures Mitral ring annuloplasty Diameter (mm) 28 mm 30 mm 32 mm Anterior leaflet procedure Posterior leaflet procedure Bileaflet procedure Other surgical procedures Atrial septal defect closure Aortic valve replacement Coronary artery bypass Maze Tricuspid valve repair Vasoactive medications post-CPB None Number with 2⫹ medications Phosphodiesterase inhibitor Epinephrine Dopamine Dobutamine Norepinephrine Vasopressin Nitroglycerin
66.1 (⫾ 15.4) 170.1 (⫾11.5) 75.4 (⫾13.6) 1.86 (⫾0.2)
All 5 mild; 8 trace; 2 none 1 severe 3 severe; 6 moderate; 14 mild; 2 none
29.5 (⫾1.5) 9 11 5 4 16 5 1 1 2 4 9
2 11 12 8 5 2 9 1 4
NOTE. Unless specified, data are listed as absolute number. Vasoactive medications are those administered after CPB (ie, during the transesophageal echocardiography examination.)
patients had atrial fibrillation. For all patients, the heart rates were below 100 beats/min. Hemodynamic and echocardiographic data are listed in Tables 2 and 3. Data were recorded as mean ⫾ standard deviation (SD). Compared with the intraoperative period, the postoperative LVEF and the PASPs were significantly higher, whereas the heart rates were lower. Although the cardiac outputs, heart rates, and pulmonary artery pressures differed, the Doppler stroke volumes (SVs) were similar among the 3 different time periods. During the intraoperative TEE examination, there was less than 1⫹ MR in all cases. Two patients had 1 to 2⫹ MR during the predischarge TTE, and 4 had 1 to 2 ⫹ MR during the follow-up TTE. All others had ⬍1⫹ MR at the time of the echocardiographic examination. At all time periods, there was no significant TR or AI (⬍1⫹). There were no congenital lesions observed during these examinations. There were significant differences (p ⬍ 0.05) in the mean
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Table 2. Hemodynamic Data Obtained at Each Time Period
Post-CPB TEE TTE-1 TTE-2
LVEF
AI
HR
mBP
CVP
PASP
TDCO
SV TDCO
DCO
SV DCO
37.9 (8.0) 46.9 (12.7)‡§ 55.7 (9.8)‡
0.2 (0.3) 0.1 (0.3) 0.1 (0.4)
91.0 (7.6) 79.2 (9.0)‡ 73.8 (12.8)‡
69.2 (6.9) NA NA
9.6 (3.7) NA NA
28.0 (12.4) 37.9 (8.9)‡ 35.5 (8.4)†§
5.91 (1.46) NA NA
65.8 (19.5) NA NA
6.14 (1.57) 4.91 (1.34)* 4.85 (1.09)‡
68.2 (20.2) 62.7 (14.7) 64.9 (18.3)
NOTE. Data are listed as the mean ⫾ standard deviations. During the postoperative examinations (transthoracic echocardiogram 1 and transthoracic echocardiogram 2) blood pressure, central venous pressure and thermodilution cardiac outputs were not available (NA). Abbreviations: AI, aortic valve insufficiency; CVP, central venous pressure; DCO, Doppler cardiac output; HR, heart rate; mBP, mean systemic blood pressure; PASP, pulmonary artery systolic pressure; SV, stroke volume; TDCO, thermodilution cardiac output; TEE, transesophageal echocardiography; TTE, transthoracic echocardiography. *p ⬍ 0.05 versus post-CPB TEE. †p ⬍ 0.01 versus post-CPB TEE. ‡p ⬍ 0.001 versus post-CPB TEE. §p ⬍ 0.05 versus TTE-1.
MV TVI, which were greater during the predischarge TTE (29.4 ⫾ 6.0 cm) and the follow-up TTE (30.2 ⫾ 6.6 cm) compared with that recorded immediately after CPB (24.9 ⫾ 11.1 cm). Postoperative mean transvalvular gradients (predischarge TTE and follow-up TTE) were significantly higher than that obtained during the intraoperative examination (Table 3). There were 3 patients with an intraoperative post-repair transmitral mean gradient ⱖ6 (6, 6, and 7) and/or a peak gradient ⱖ10 (10, 12, and 14) mmHg. For these patients, the MVA was 2.7, 2.6, and 2.5 cm2, with respective cardiac outputs of 8.6, 9.0, and 9.3 L/min (heart rate of 90, 98, and 90, respectively). Otherwise, all mean gradients were ⬍6 mmHg. The PHT method was feasible in all patients studied. The 2D-PLAN was feasible in 19 of 25 (76%) of the intraoperative TEE cases and in 21 of 25 (84%) and 22 of 25 (88%) of predischarge TTE and follow-up TTE cases, respectively. The inability to perform planimetry was caused by poor visualization of all the leaflet edges in the same plane. The CE was feasible in 23 of 25 (92%) intraoperative cases, 22 of 25 (88%) during predischarge TTE, and all cases during follow-up TTE. Difficulties in performing the CE included difficulty measuring the diameter of the reference site (n ⫽ 2) and/or difficulty aligning the Doppler beam with blood flow (n ⫽ 3).
MVA data using the CE were significantly lower than data obtained using other methods at each time period. MVA data using the CE were lowest during the 2 postoperative examinations: a predischarge TTE and a TTE 6 to 12 months after surgery (Table 3). If mitral stenosis was considered to be an MVA ⬍1.8 cm2, then, based on PHT or 2D-PLAN, no patient had stenosis. Based on CE data, 1 (4%), 3 (14%), and 4 (16%) patients would have been considered to have mitral stenosis during the intraoperative and 2 postoperative examinations, respectively. At all time periods, there was good agreement between MVA data obtained with PHT and PLAN, whereas agreement between the CE data and other methods yielded larger mean biases (Tables 4-6). Correlation analyses yielded a range of results among the different examinations and time periods (Figs 1 and 2). Very good correlations (r ⱖ 0.80, p ⬍ 0.001) were found between the following: intraoperative PHT with intraopertive 2D-PLAN (r ⫽ 0.85, y ⫽ 0.47 ⫹ 0.86 x), intraoperative PHT with follow-up TTE PHT (r ⫽ 0.88; y ⫽ 0.38 ⫹ 0.86 x), and intraoperative 2D-PLAN and follow-up TTE PHT (r ⫽ 0.81, y ⫽ 0.45 ⫹ 0.84 x). Other comparisons showed lower r values (r ⬍ 0.80 and p ⬍ 0.05) but still significant correlations. These included comparisons between intraoperative PHT and postoperative 2D-PLAN
Table 3. Echocardiographic Data Including MVA Obtained by PHT, Planimetry, and the Doppler CE During the Intraoperative (Operating Room) TEE Examination Immediately After Separation From CPB, the TTE (TTE 1) Examination Before Hospital Discharge, and the Late TTE Examination 6 to 12 Months After Surgery (TTE 2)
Post-CPB TEE TTE 1 TTE 2
PHT
Planimetry
Doppler CE
Peak Gradient
Mean Gradient
2.96 (0.50)*ठ2.14-4.08 2.96 (0.68)ठ2.00-4.89 3.02 (0.49)*ठ2.26-4.30
2.99 (0.55)ठ1.90-3.80 2.91 (0.51)ठ1.83-3.90 3.07 (0.35)ठ2.51-3.80
2.71 (0.66)†‡$ 1.21-3.96 2.33 (0.56)*† 1.52-3.46 2.40 (0.70)*† 1.30-3.97
6.4 (2.3) 3.0-12.0 9.3 (2.6)储 3.8-12.0 8.5 (3.4)储¶ 3.5-18.0
3.3 (1.2) 1.0-1.6 4.1 (1.2) 2.1-7.0 3.5 (1.5) 1.0-7.0
NOTE. All data are presented as the mean (standard deviation); CE, reference flow using Doppler. *p ⬍ 0.01 versus the post-CPB transesophageal echocardiographic CE Doppler. †p ⬍ 0.05 versus the post-CPB transesophageal echocardiographic CE thermodilution. ‡p ⬍ 0.01 versus the predischarge TTE CE. §p ⬍ 0.01 versus the late transesophageal echocardiographic CE. 储p ⬍ 0.01 versus the post-CPB gradient. ¶p ⬍ 0.001 versus the TTE 1 gradient.
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Table 4. Agreement Between Methods of MVA Measurement Within Each Study Period Operating Room Post-CPB
Mean MVA Bias
TTE 1
TTE 2
PHT and PLAN
PHT and CE
PLAN and CE
PHT and PLAN
PHT and CE
PLAN and CE
PHT and PLAN
PHT and CE
PLAN and CE
2.96 (0.53) ⫺0.04 (0.29)
2.84 (0.54) 0.26 (0.51)
2.89 (0.50) 0.16 (0.43)
2.94 (0.58) 0.07 (0.51)
2.63 (0.47) 0.59 (0.86)
2.57 (0.48) 0.56 (0.56)
3.09 (0.39) 0.03 (0.37)
2.72 (0.52) 0.59 (0.66)
2.80 (0.52) 0.58 (0.61)
NOTE. Data include mean bias and standard deviations. Data are presented as centimeters squared. Abbreviations: TTE 1, predischarge transthoracic echocardiographic examination; TTE 2, 6- to 12-month transthoracic echocardiographic examination.
that were fair (predischarge TTE, r ⫽ 0.72; follow-up TTE, r ⫽ 0.65). The correlation between intraoperative 2D-PLAN and postoperative 2D-PLAN also was fair (predischarge TTE, r ⫽ 0.76; follow-up TTE, r ⫽ 0.65). Correlation results involving the CE varied from r ⫽ ⫺0.19 to 0.65, with the majority being less than 0.6. The lower correlations and agreement between CE and other MVA data were not improved by omitting patients with postoperative atrial fibrillation and/or MR ⱖ2⫹. Using the different measures of MVA, the incidence of PPM based on the intraoperative examination was 12.5%, 16.7%, and 27.3% for PHT, planimetry, and CE, respectively. During the predischarge TTE, the incidence was 13.0%, 5.3%, and 52.6% for PHT, planimetry, and CE, respectively. During the late TTE, the incidence was 9.1%, 5.3%, and 59% for PHT, planimetry, and CE, respectively. There were no significant correlations between MVA and transvalvular gradients at any of the time periods. When analyzing iMVA several moderate (r ⫽ ⫺0.54 to ⫺0.69) but statistically significant (p ⬍ 0.01) correlations between intraoperative iMVA (PHT and planimetry, respectively) and the mean intraoperative transvalvular gradient were found. Other correlations between MVA data and pressure gradients failed to reach significance. Interobserver variability was assessed using agreement statistics between 2 echocardiographers. During the intraoperative examination, the mean biases (⫾SD) for 2D-PLAN (⫺0.29 cm2 ⫾ 0.45), CE MVA (0.31 cm2 ⫾ 0.45), and PHT (0.14 cm2 ⫾ 0.35) were found. Compared with the mean MVA data for each method, these corresponded to a 10% (2DPLAN), 11% (CE MVA), and a 5% (PHT) difference between the 2 examiners. During the follow-up TTE examination, the mean biases (⫾SD) for 2D-PLAN (⫺0.58 cm2 ⫾ 0.95), CE MVA (⫺0.23 cm2 ⫾ 0.50), and PHT (0.17 cm2 ⫾ 0.47) were recorded. Compared with the mean MVA data for each method, these corresponded to an 18% (2D-PLAN), 10% (CE-MVA), and a 6% (PHT) difference between the 2 examiners.
DISCUSSION
This study showed that the intraoperative measurement of MVA, using PHT and 2D-PLAN, had good agreement and correlation with respective data obtained in the postoperative time periods. By contrast, MVAs calculated by the CE were lower than and did not correlate as well with MVA data obtained using PHT or 2D-PLAN. Overall, the PHT technique was more feasible than other methods, whereas 2D PLAN was the least. The intraoperative TEE assessment of the repaired MV is important to determine surgical success and guide further management.6,7,10 Although the assessment of post-repair regurgitation mirrors that used with native valves, the evaluation of valve patency has not been established. Level 1 recommendations for assessing native valve patency include transvalvular pressure gradients, 2D-PLAN, and PHT; however, after MV procedures (repair or replacement), these techniques are not well studied and may be affected by physiologic and anatomic changes.11,12,21 The present study is the second intraoperative study to assess MVA after repair and the first to compare the different methods of assessment. In the one other intraoperative study, the mean intraoperative MVA, assessed by TEE using PHT underestimated the mean postoperative TTE value (2.1 ⫾ 0.5 cm2 v 2.7 ⫾ 1.0 cm2) performed (PHT) on average 10 weeks later.7 For 5 patients, the intraoperative value would have resulted in revision of the repair.7 As a result, Poh et al7 concluded that intraoperative PHT was not an accurate reflection of valve patency and suggested that a mean transvalvular pressure gradient ⱖ10 mmHg may be the better measure of post-repair stenosis. The present authors recently reported a case in which postrepair stenosis was suspected based on 2D-PLAN and PHT but not by the Doppler pressure gradient (peak ⫽ 6 mmHg).10 Direct measurement of the pressure gradient was elevated significantly (16 mmHg), confirming-post repair stenosis and showing the limitations of a Doppler-assessed gradient after
Table 5. Agreement Between Methods of the MVA Measurement for Each Method and Between Time Periods PHT
Planimetry
CE
OR and TTE 1 OR and TTE 2 TTE 1 and TTE 2 OR and TTE 1 OR and TTE 2 TTE 1 and TTE 2 OR and TTE 1 OR and TTE 2 TTE 1 and TTE 2
Mean MVA Bias
2.98 (0.53 0.03 (0.53)
3.01 (0.47) ⫺0.03 (0.24)
3.03 (0.55) ⫺0.05 (0.48)
3.00 (0.48) 0.19 (0.36)
3.12 (0.36) 0.12 (0.35)
3.08 (0.36) ⫺0.11 (0.31)
2.50 (0.53 0.32 (0.67)
2.52 (0.65) 0.32 (0.48)
2.31 (0.48) ⫺0.06 (0.86)
NOTE. Data include mean bias and standard deviations. Data are presented as centimeters squared. Abbreviations: OR, operating room; TTE 1, predischarge transthoracic echocardiographic examination; TTE 2, 6- to 12-month transthoracic echocardiographic examination.
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Table 6. Agreement Between the Intraoperative MVA Measurement Obtained With the PHT and 2D-PLAN Obtained During the Early (TTE 1) and Late (TTE 2) Echocardiographic Follow-up
Mean MVA Bias
OR PHT and TTE 1 PLAN
OR PHT and TTE 2 PLAN
2.98 (0.46) 0.15 (0.37)
3.07 (0.39) ⫺0.01 (0.37)
NOTE. Data are presented as centimeters squared. Abbreviations: TTE 1, predischarge transthoracic echocardiographic examination; TTE 2, 6- to 12-month transthoracic echocardiographic examination.
repair.10-12 Pressure gradients offer a simple estimation of valve patency and are clinically important because they represent the degree of pressure load to the atrium and pulmonary vasculature. Previously defined parameters for mitral stenosis (MVA ⱕ1.8 cm2) include mean and peak gradients ⱖ6 and 12 mmHg, respectively.11,22 Gradients, however, are dependent on other variables besides valve area, including blood flow, heart rate, net AV compliance, and the angle of interrogation between the ultrasound beam and blood flow. The latter may be an important issue for the repaired valve.10-12,23 In the present study, there were 3 patients with a mean intraoperative gradient ⱖ6 mmHg, and none was associated with mitral stenosis (MS) by any measure of MVA. In addition, no significant correlation was found between intraoperative transvalvular pressure gradients and MVA data. Therefore, echocardiographers should not rely solely on the pressure gradients to assess valve patency after repair. The PHT is easy to obtain, has acceptably low inter- and intraobserver variability, and has been shown to be accurate over a wide range of MVAs.11,12,24 Compared with pressure gradients, the PHT is less affected by changes in heart rate and ultrasound interrogation angles, the latter remaining accurate with angles up to 40°.11,13 It is, however, affected by changes in net AV compliance, pressure gradients, and cardiac outputs.12,13,24,25-29 For patients with MS, acute changes in these
Fig 1. A regression figure of the MVA data measured using the PHT obtained immediately after MV repair and during the later follow-up (follow-up transthoracic echocardiogram). There was a good correlation between the 2 datasets (r ⴝ 0.88, y ⴝ 0.36 ⴙ 0.86 x, p < 0.0001).
variables, as seen experimentally24 and after percutaneous valvuloplasty,26-28 affect the accuracy of the PHT to calculate the MVA. The relief of MS acutely changes left atrial (LA) function, whereas MV surgery for MR acutely increases left ventricular afterload and dysfunction, which also may affect LA function.30,31 Patients with pure MR (ie, no preoperative stenosis) may experience a minimal change in net AV compliance after MV surgery.30,31 If this is the case, then the PHT will vary with the MVA as described previously (MVA ⫽ 220/PHT).24 The limitations of PHT, as described in patients with MS, may not apply to patients undergoing valve surgery for MR.7,12,26-29 The present study does not necessarily contradict the findings by Poh et al7 but, instead, highlights the importance of reporting and optimizing hemodynamic function during the assessment of MVA after repair.4,9 Compared with the study by Poh et al in which hemodynamic data were limited to heart rate and blood pressure, the present study used more invasive monitoring and a more aggressive hemodynamic management protocol immediately after MV repair. The effect of hemodynamic function on MVA is more pronounced for valves with greater leaflet mobility and potential for annular expansion.13,14,32-37 In 2 studies, one using 2D-PLAN and another using PHT, the MVA of the repaired valve increased approximately 30% during exercise and correlated with increases in SV and heart rate.4,9 Although these reports involved Alfieri repairs, the principle relating hemodynamics to MV function should be similar, or perhaps greater, with other repair techniques that do not restrict leaflet motion. The repaired valve has reserve function, and the assessment of MVA should be performed when hemodynamic function is optimized. Two-dimensional planimetry is a direct measurement of MVA and was shown to best correlate with the area of explanted rheumatic stenotic valves.38 Therefore, 2D-PLAN is considered the reference to compare other measures of MVA.11,22 However, for nonplanar or “dome-shaped” valves, its accuracy and feasibility are reduced for both TTE (feasibility 89%) and TEE (feasibility 69%) because of difficulties in imaging all leaflet edges in the same plane.21,39-42 This is also an
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Fig 2. A regression figure of the MVA data measured using the PHT and 2D-PLAN. The former was obtained during the intraoperative examination, whereas the latter was obtained during the later follow-up (follow-up transthoracic echocardiogram). There was a good correlation between the 2 datasets (r ⴝ 0.85, y ⴝ 0.47 ⴙ 0.86 x, p < 0.0001).
issue after MV repair.21 Three-dimensional imaging with offline planimetry (3D-PLAN) may obviate the problems with nonplanar structures by identifying the narrowest orifice21,23,41; however, its intraoperative online application has not been reported. A TTE study after MV repair noted that 3D-PLAN correlated and agreed with PHT more than with 2D-PLAN because of the difficulty in imaging the leaflet edges during 2-dimensional interrogation.21 This is the first study to examine MVA assessment using the CE after repair. As could be expected, MVA data measured by the CE was lower than MVA data from PHT and 2D-PLAN. This difference is the coefficient of contraction.11,43,44 The CE assesses flow at the vena contracta and calculates the effective valve area, which could be as low as 65% to 85% of the anatomic MVA, as measured by the Gorlin equation.11,43,44 Although a lower MVA by the CE could have been anticipated at all time points, it does not explain why intraoperative CE MVAs were greater than postoperative CE MVAs or why the correlation between CE MVA and other MVA data was low. Omitting patients with ⱖ2⫹ MR during the postoperative TTE did not improve the correlation. Measurement errors or inaccuracies could help to explain the CE data. Although Doppler-measured velocity data obtained with either HPRF or CW Doppler have been reported to be similar,45 other data have not.46 The latter study reported poor correlation at lower velocities and underestimation by HPRF at higher velocities.46 A lower intraoperative MV TVI obtained with HPRF would result in a higher MVA compared with the respective data obtained with CW Doppler. Although this may help to explain why intraoperative CE MVA data were higher than postoperative, it does not explain the lack of correlation between CE data (intraoperative or postoperative) and other MVA data obtained with PHT or 2D-PLAN. The authors speculate that the results were likely caused by measurement errors, reflecting the multiple variables needed to perform the CE.11,47 Although the authors do not discount the possibility that the CE might be a useful measure of MVA after repair, they do caution against its use based on the data presented here.
In the absence of a gold standard, it is still unknown as to which measure of MVA is accurate or clinically important. Previous reports show a good correlation among different echocardiographic methods, including PHT, when the MVA is ⬍2.0 cm2 under varying hemodynamic conditions.32,34 A postoperative study of patients after MV repair found 3D-PLAN to agree with 2D-PLAN and PHT.21,41 If intraoperative and postoperative data agree, as shown in the present study, and 3D-PLAN is considered a reference method, then it might be speculated that intraoperative MVA assessment of the repaired valve is feasible and accurate. However, an intraoperative investigation comparing 3D-PLAN with 2D-PLAN and PHT has not been performed to confirm this statement. Without a clinical correlate, it is difficult to know what method of measurement is important and/or below what MVA is considered problematic after valve repair. For the native valve, mitral stenosis has been defined as ⬍1.8 cm2 and associated with increased transvalvular gradients, left atrial dysfunction and arrhythmias, pulmonary hypertension, and heart failure.11 Although it is uncommon to record a prosthetic or post-repair MVA ⬍1.8 cm2, investigators have described PPM for the prosthetic valve as an iMVA of ⬍1.2 to 1.3 cm2/m2.17-19 In these studies, PPM was associated with increased morbidity and mortality.17-19 Using a similar definition, PPM, in the present study, occurred between 5% and 12% for data obtained using PHT and 2D-PLAN and 25% to 60% using CE data. A significant correlation was found between transvalvular gradients and the iMVA data obtained using PHT and 2D-PLAN but not with CE data. Although the transvalvular gradient represents the pressure load on the LA and pulmonary veins, the absence of a long-term follow-up makes any conclusion regarding the importance of PPM on the repaired valve premature. Limitations Measures of net AV compliance were not performed in the present study. Although some direct and indirect measures of heart function (ie, PASP, SV, and LVEF) were recorded, it was
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not possible to make assumptions regarding chamber compliance. The authors cannot eliminate a potential bias during a given time period because the measurements were obtained by the same echocardiographer. Good agreement between the measures of MVA during each time period could have been affected by this bias. However, the intraoperative and postoperative examinations were assessed by different echocardiographers, each being blinded to the respective data; therefore, the correlations between intraoperative and postoperative MVA data should not be affected. The measurement of transmitral flow velocities between time points should have been better standardized. The use of HPRF during the intraoperative period could explain the differences between intraoperative and postoperative CE data, and to a lesser extent, the correlation with other methods.45 Theoretically, the HPRF allows measurement of higher-velocity flows (compared with PW Doppler) with less range ambiguity than CW Doppler. Although previously published data showed accurate assessment of peak velocity with HPRF when compared with CW,46 others noted that HPRF underestimates peak velocities compared with CW Doppler, particularly with highervelocity flows.45
Finally, the interobserver variability was greater for 2DPLAN and the CE than for the PHT. This likely reflects the simplicity of the PHT method compared with PLAN and the CE and has been shown by others. Although the variability among the PHT data was lowest, the standard deviation was high enough such that 2 different examiners may conclude different levels of valve function. As guidelines suggest for native valve stenosis, a comprehensive evaluation of valve patency after repair should synthesize multiple methods and measurements. CONCLUSION
The present study showed that the MVA, assessed by PHT or 2D-PLAN, recorded intraoperatively after valve repair agreed and correlated with MVA data obtained with similar methods in the early and late postoperative period. The discrepancy with the one other intraoperative study highlights the importance of optimizing hemodynamics during assessment of MVA. Although the present study found similar MVA when assessed at different time periods, the authors could not conclude whether PHT or PLAN should be used as a reference or gold standard. Future study should compare intraoperative echocardiographic measurements with 3D-PLAN.
REFERENCES 1. Unger-Graeber B, Lee RT, Sutton MS, et al: Doppler echocardiographic comparison of the Carpentier and Duran annuloplasty rings versus no ring after mitral valve repair for mitral regurgitation. Am J Cardiol 67:517-519, 1991 2. Sakamoto Y, Hashimoto K, Okuyama H, et al: Long-term assessment of mitral valve reconstruction with resection of the leaflets: Triangular and quadrangular resection. Ann Thorac Surg 79:475-479, 2005 3. Kobayashi Y, Nagata S, Ohmori F, et al: Mitral valve dysfunction resulting from thickening and stiffening of artificial mitral valve chordae. Circulation 94:II129-II132, 1996 4. Umana JP, Salehizadeh B, DeRose JJ Jr, et al: “Bow-tie” mitral valve repair: An adjuvant technique for ischemic mitral regurgitation. Ann Thorac Surg 66:1640-1646, 1998 5. Ibrahim MF, David TE: Mitral stenosis after mitral valve repair for non-rheumatic mitral regurgitation. Ann Thorac Surg 73:34-36, 2002 6. Brinster DR, Unic D, D’Ambra M, et al: Midterm results of the edge-to-edge technique for complex mitral valve repair. Ann Thorac Surg 81:1612-1617, 2006 7. Poh KK, Hong EC, Yang H, et al: Transesophageal echocardiography during mitral valve repair underestimates mitral valve area by pressure half-time calculation. Int J Cardiol 108:177-180, 2006 8. Camilleri LF, Miguel B, Bailly P, et al: Flexible posterior mitral annuloplasty: Five-year clinical and Doppler echocardiographic results. Ann Thorac Surg 66:1692-1697, 1998 9. Agricola E, Maisano F, Oppizzi M, et al: Mitral valve reserve in double-orifice technique: An exercise echocardiographic study. J Heart Valve Dis 11:637-643, 2002 10. Maslow AD, Singh A, Mahmood F, et al: Intraoperative assessment of mitral valve area after mitral valve repair for regurgitant valves. J Cardiothorac Vasc Anesth 25:221-228, 2011 11. Baumgartner H, Jung J, Bermejo J, et al: Echocardiographic assessment of valve stenosis: EAE/ASE recommendation for clinical practice. J Am Soc Echocardiogr 22:1-23, 2009
12. Zoghbi WA, Chambers JB, Dumesnil JG, et al: Recommendations for evaluation of prosthetic valves with echocardiography and Doppler ultrasound. J Am Soc Echocardiogr 22:975-1014, 2009 13. Hatle L, Angelsen B, Tromsdal A: Noninvasive assessment of atrioventricular pressure half-time by Doppler ultrasound. Circulation 60:1096-1104, 1979 14. Hatle L, Brubakk A, Tromsdal A, et al: Noninvasive assessment of pressure drop in mitral stenosis by Doppler ultrasound. Br Heart J 40:131-140, 1978 15. Lim E, Ali ZA, Barlow CW, et al: Determinants and assessment of regurgitation after mitral valve repair. J Thoracic Cardiovasc Surg 124:911-917, 2002 16. Zoghbi WA, Enriquez-Sarano M, Foster E, et al: American Society of Echocardiography. Recommendations for evaluation of the severity of native valvular regurgitation with two-dimensional and Doppler echocardiography. J Am Soc Echocardiogr 16:777802:2003 17. Lam BK, Chan V, Hendry P, et al: The impact of patientprosthesis mismatch on late outcomes after mitral valve replacement. J Thorac Cardiovasc Surg 133:1464-1473, 2007 18. Li M, Dumesnil JG, Mathieu P, et al: Impact on valve prosthesis-mismatch on pulmonary arterial pressure after mitral valve replacement. J Am Coll Cardiol 45:1034-1040, 2005 19. Aziz A, Lawton JS, Maniar HS, et al: Factors affecting survival after mitral valve replacement in patients with patients prosthesis mismatch. Ann Thorac Surg 90:1202-1211, 2010 20. Ommen SR, Nishimura RA, Hurrell DG, et al: Assessment of right atrial pressure with 2-dimensional and Doppler echocardiography: A simultaneous catheterization and echocardiographic study. Mayo Clin Proc 75:24-29, 2000 21. Hoole SP, Liew TV, Boyd J et al: Transthoracic real-time three-dimensional echocardiography offers additional value in the assessment of mitral valve morphology and area following mitral valve repair. Europ J Echocardiogr 9:625-630, 2008
228
22. Bonow RO, Carabello BA, Chatterjee K, et al: ACC/AHA 2006 guidelines for the management of patients with valvular heart disease. J Am Coll Cardiol 48:e1-e148, 2006 23. Green GR, Dagum P, Glasson JR, et al: Restricted posterior leaflet motion after mitral ring annuloplasty. Ann Thorac Surg 68:21002106, 1999 24. Thomas JD, Weyman AE: Doppler mitral pressure half-time: A clinical tool in search of theoretical justification. J Am Coll Cardiol 10:923-929, 1987 25. Stoddard MF, Prince CR, Tuman WL, et al: Angle of incidence does not affect accuracy of mitral stenosis area calculation by pressure half-time: Application to Doppler transesophageal echocardiography. Am Heart J 127:1562-1572, 1994 26. Zamorano J, Perez de Isla L, Sugeng L, et al: Non-invasive assessment of mitral valve area during percutaneous balloon mitral valvuloplasty: Role of real-time 3D echocardiography. Eur Heart J 25:2086-2091, 2004 27. Sunil Roy TN, Krishnan MN, Koshy C, et al: Comparison of proximal isovelocity surface area method and pressure half time method for evaluation of mitral valve area in patients undergoing balloon mitral valvotomy. Echocardiography 22:707-712, 2005 28. Thomas JD, Wilkins GT, Choong CY, et al: Inaccuracy of mitral pressure half-time immediately after percutaneous mitral valvotomy. Dependence on transmitral gradient and left atrial and ventricular compliance. Circulation 78:980-993, 1988 29. Kim HK, Kim YJ, Chang SA, et al: Impact of cardiac rhythm on mitral valve area calculated by the pressure half time method in patients with moderate or severe mitral stenosis. J Am Soc Echocardiogr 22:42-47, 2009 30. Zile MR, Gaasch WH, Levine HJ: Left ventricular stress dimension-shortening relation before and after correction of chronic aortic and mitral regurgitation. Am J Cardiol 56:99-105, 1985 31. Wong CYH, Spotnitz HM: Systolic and diastolic properties of the human left ventricle during valve replacement for chornic mitral regurgitation. Am J Cardiol 47:40-50, 1981 32. Loperfido F, Laurenzi F, Gimigliano F, et al: A comparison of the assessment of mitral valve area by continuous wave Doppler and by cross sectional echocardiography. Br Heart J 57:348-355, 1987 33. Libanoff AJ, Rodbard S: Atrioventricular pressure half-time. Measure of mitral valve orifice area. Circulation 38:144-150, 1968 34. Braverman AC, Thomas JD, Lee RT: Doppler echocardiographic estimation of mitral valve area during changing hemodynamic conditions. Am J Cardiol 68:1485-1490, 2001 35. Voelker W, Karsch KR: Exercise Doppler echocardiography in conjunction with right heart catheterization for the assessment of mitral stenosis. Int J Sports Med 17:S191-S195, 1996
MASLOW ET AL
36. Voelker W, Berner A, Regele B, et al: Effect of exercise on valvular resistance in patients with mitral stenosis. J Am Coll Cardiol 22:777-782, 1993 37. Dahan M, Paillole C, Martin D, et al: Determinants of stroke volume response to exercise in patients with mitral stenosis: A Doppler echocardiographic study. J Am Coll Cardiol 21:384-389, 1993 38. Faletra F, Pezzano A Jr, Fusco R, et al: Measurement of mitral valve area in mitral stenosis: Four echocardiographic methods compared with direct measurement of anatomic orifices. J Am Coll Cardiol 28:1190-1197, 1996 39. Stoddard MF, Prince CR, Ammash NM, et al: Two-dimensional transesophageal echocardiograhic determination of mitral valve area in adults with mitral stenosis. Am Heart J 127:1348-1353, 1994 40. Binder TM, Rosenhek R, Porenta G, et al: Improved assessment of mitral valve stenosis by volumetric real-time three-dimensional echocardiography. J Am Coll Cardiol 36:1355-1361, 2000 41. Chen Q, Nosiir YM, Vietter WB, et al: Accurate assessment of mitral valve area in patients with mitral stenosis by three-dimensional echocardiography. J Am Soc Echocardiogr 10:133-140, 1997 42. Sugeng L, Weinert L, Lammertin G, et al: Accuracy of mitral valve area measurements using transthoracic rapid freehand 3-dimensional scanning: Comparison with noninvasive and invasive methods. J Am Soc Echocardiogr 16:1292-1300, 2003 43. Gilon D, Cape EG, Handschumacher MD, et al: Effect of three-dimensional valve shape on the hemodynamics of aortic stenosis: Three-dimensional echocardiographic stereolithography and patient studies. J Am Coll Cardiol 40:1479-1486, 2002 44. Bitar JN, Lechin ME, Salazar G, et al: Doppler echocardiographic assessment with the continuity equation of St Jude Medical mechanical prostheses in the mitral valve position. Am J Cardiol 76:287-293, 1995 45. Snider AR, Stevenson JG, French JW, et al: Comparison of high pulse repetition frequency and continuous wave Doppler echocardiography for velocity measurement and gradient prediction in children with valvular and congenital heart disease. J Am Coll Cardiol 7:873879, 1986 46. Stewart WJ, Galvin KA, Gilliam LD, et al: Comparison of high pulse repetition frequency and continuous wave Doppler echocardiography in assessment of high flow velocity in patients with valvular stenosis and regurgitation. J Am Coll Cardiol 6:565-571, 1985 47. Bednarz JE, Krauss D, Long RM: An echocardiographic approach to the assessment of aortic stenosis. J Am Soc Echocardiog 9:286-294, 1996