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Value of proximal regurgitant jet size in tricuspid regurgitation
Valvular Heart Disease
Value of proximal regurgitant jet size in tricuspid regurgitation J. Miguel Rivera, MD, PhD, a Peter Vandervoort, M D ? Donato Mele, MD, c Arthur Weyman, MD, d J a m e s D. Thomas, MD b Valencia, Spain, Cleveland, Ohio, Ferrara, Italy, and Boston, Mass.
Recent studies have shown good agreement between proximal regurgitant jet size obtained with transthoracic color flow mapping and regurgitant fraction in patients with mitral regurgitation. To evaluate this in patients with tricuspid regurgitation, we analyzed 40 patients in sinus rhythm, 16 with free jets and 24 with impinging jets, comparing proximal jet size (millimeters) with parameters derived from the Doppler two-dimensional echocardiographic method (regurgitant fraction) and the flow-convergence method (peak flow rate, effective regurgitant orifice area, and momentum). Good agreement was noted between peak flow rate (r= 0.80, p < 0.001), momentum (r= 0.80, p < 0.001), and effective regurgitant orifice area (r = 0.78, p < 0.001), with proximal jet size measured in the apical four-chamber view in patients with free jets. The average of jet proximal size in three planes also had good correlation with peak flow rate (r= 0.75, p < 0.001), regurgitant fraction, momentum, and effective regurgitant orifice area (r= 0.74, p < 0.001). In patients with impinging jets, agreement was fair between effective regurgitant orifice (r=0.65, p<0.001), peak flow rate (0.65, p < 0.001), and momentum (r= 0.62, p < 0.001) with mean jet proximal size. Jet proximal size obtained with transthoracic color flow mapping is a good semiquantitative tool for measuring tricuspid regurgitation in free jets that correlates well with established measures of the severity and with new parameters available from analysis of the proximal acceleration field. In patients with eccentrically directed wall jets, the correlation weakens but still appears clinically significant. (AM HEARTJ 1996;131:742-7.)
The arrival of color Doppler flow mapping has significantly improved the noninvasive evaluation of patients with valvular incompetence. 1 Visualization From aCentro de Investigacion Cardiocirculatoria, Hospital La Fe, Valencia; the bCardiology Department, Cleveland Clinic Foundation; the c Cardiology Department, Ospedale Civile, Ferrara; and the dCardiology Department, Massachusetts General Hospital and Harvard Medical School, Boston. Received for publication July 18, 1995; accepted Sept. 1, 1995. Reprint requests: J. Miguel R~vera, MD, PhD, c/Periodista Badia 11, pt 1, Valencia 46010, Spain. Copyright © 1996 by Mosby-Year Book, Inc. 0002-8703/96/$5.00 + 0 4/1/70063
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of jet area allows useful simultaneous semiquantitative grading of regurgitation, which permits immediate therapeutical decisions. Despite known limitations, 2 visual assessment has become the most common method used in daily clinical practice. Nevertheless, it has been shown that jet size correlates only weekly with regurgitant flow. Recently described quantitative parameters (peak flow rate, momentum, and effective regurgitant orifice area) have been found to influence jet areas in theoretic and in vitro studies 3, 4 and are now easily obtainable clinically from the proximal flow-convergence method. 5"7 Furthermore, in patient s with impinging jets, the correlation between jet dimensions and all these factors is poor. s Recently good agreement between proximal regurgitant jet size as imaged with transthoracic Doppler echocardiography and regurgitant flow has been described in patients with mitral and aortic insufficiency. 9, 10 This proximal dimension of the jet as it emerges from the orifice has been shown to increase with the size of the regurgitant orifice under clinical ranges of flow and driving pressures 11 and has the advantage of being measured before the point of impingement and being easy to perform. However, this method has not been tested in tricuspid regurgitation. The purpose of this study, therefore, was to evaluate the predictive value of proximal jet measurement when compared with regurgitant fraction and identify physical factors that influence its size in patients with tricuspid regurgitation. METHODS
Patients were studied by one research technician and were screened for the following selection criteria: (1) the presence of tricuspid regurgitation in the color Doppler display; (2) the presence of a proximal flow-convergence region on the color Doppler display at the ventricular surface of the tricuspid leaflets in at least one view obtained from a surface standardized-scanning plane; (3) availabil-
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ity of high-quality, two-dimensional images and Doppler tracings to allow accurate tricuspid and pulmonary flow calculations with the Doppler/two-dimensional echocardiographic method. 1214 Patients with tricuspid stenosis, accompanying pulmonary valve disease, or intracardiac shunt flow were excluded. Forty patients met the criteria for the study (22 women and 18 men) with a mean age of 66 _+ 15 years (age range 34 to 89 years). All 40 patients were in sinus rhythm at the time of the study. The underlying cardiac diseases included ischemic heart disease in 20 patients, mitral valve prolapse in 3, mitral rheumatic heart disease in 11, pericardial effusion in 2, and absence of detectable morphologic lesions in 4.
Echocardiographic data. All two-dimensional, pulsed, and color Doppler flow data were obtained as part of the routine echocardiographic evaluation. Commercially available Doppler echocardiography machines (Hewlett-Packard 77020A or Sonos 1000, Andover, Mass.), equipped with a standard 2.5 MHz transducer were used for the study. All images and spectral flow profiles were recorded on halfinch videotape for off-line analysis. Color Doppler images for analysis of the proximal flow convergence were obtained in parasternal long right ventricular inflow, apical four-chamber and parasternal shortaxis views at pulse repetition frequencies of 3.9 kHz to 4.8 kHz. The typical Nyquist velocity was 58 cm/sec at a scanning depth of 16 cm. Each color Doppler examination was performed with the narrowest sector angle possible (30 degrees) to maximize the color flow imaging frame rate (15 to 17 Hz). Data analysis. All M-mode tracings, two-dimensional images, Doppler spectra, and color Doppler images were analyzed off-line with a computer analysis system (Sony SUM 1010). All measurements were averaged at least over three cardiac cycles except for the radius measuremerit of the proximal flow convergence, as is discussed below. Doppler two-dimensional echocardiography. The overall approach to the pulsed Doppler quantification of tricuspid regurgitation has been previously detailed. With the method of Meijboom et al. 12 for calculating the tricuspid valve forward flow (VTv), the tricuspid valve flow area was determined from an apical four-chamber view. The tricuspid forward flow was determined as the product of tricuspid inflow time--velocity integral, diastolic tricuspid orifice area, and heart rate divided by cos 0. In our study, cos 0 range was 0.85 to I (0.93 -+ 0.04). Pulmonary forward flow was obtained by the method described by Goldberg et a]. 13 and Valdes-Cruz et al.14 Transpulmonary forward flow (Vpv) was calculated from the product of systolic pulmonary area, pulmonary timevelocity integral, and heart rate. In the absence of pulmonary regurgitation or abnormal shunt flow, the tricuspid regurgitant stroke volume (SV) was given as the difference between tricuspid inflow and pulmonary outflow. 13, 15 Multiplying regurgitant stroke volume (SV) by heart rate (HR) yields regurgitant flow rate Q (cm3/min), with reg~rgitant fraction obtained by SV/V~.
Rivera et al. 743 Proximalflow-convergence calculation. With the method previously described, 6 from the apical four-chamber or parasternal right ventricular-inflow view, the ventricular surface of the tricuspid valve leaflets was carefully scanned for the presence of a flow-convergence region proximal to the site of regurgitation. In this study the aliasing velocity was typically set to 19 cm/sec. By means of the proximal flow-convergence method, maximal regurgitant flow rate (Qp) was calculated as the product of the largest proximal isovelocity surface area multiplied by the velocity at that surface. Assuming simple hemispheric symmetry of the converging flow field, the proximal isovelocity surface area can be calculated as 2~r 2, where r is the radius measured from the first color alias to the regurgitant orifice. Previous work in our laboratory has demonstrated a predictable, systematic underestimation of flow rate as a result of flattening of the isovelocity contours close to the orifice, an error that can be corrected by multiplying the calculated flow rate by vp/(Vp - Va), where Vpis the peak orifice velocity (from continuous-wave Doppler) and va is the aliasing velocity of interest.16 Because this error is particularly troublesome for right-sided regurgitant lesions where Va is a significant proportion Of Vp, we applied this correction factor to our data. Similarly, we have shown that the proximal convergence zone may be distorted by the global geometry in which the orifice lies. 17, ~s A correction that has been validated is to multiply 2~ by d180, where a is the angle subtended by the valve leaflets. A similar correction ~kas applied here: was measured with a protractor from still-frame printouts of the valve image taken in the apical four-chamber view. Combining these corrections for local and global geometric factors yielded the following overall equation for peak instantaneous regurgitant flow rate (cm3/sec) Qp = 2~r2Va • [ ~
V
c~
]" (1-~).
Effective regurgitant orifice area (ROA) can then easily be obtained by ROA = QP.
Vp
Jet momentum was calculated at the regurgitant orifice level as the product of peak regurgitant flow times the relocity at that level. 3, 7 The flow through the orifice was calculated by using the proximal flow-convergence method, and the velocity was obtained from the continuous wave. Jet proximal size. For jet proximal size, distance was measured as close as possible to the regurgitant orifice and was traced with a light pen (Fig. 1). Jets were classified into two types: free and walk s Proximal jet size was measured in apical four-chamber and parasternal long right ventricular inflow and short-axis views. Maximum jet size in the three planes and average of three planes were also measured.
Reproducibility of measurements Proximal flow-convergence method, interobserver variability. In a previous study, 6 we calculated the inter-
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Fig. 1. Color Doppler echo view of patient with tricuspid regurgitation shows measurement of proximal jet width (arrows) as it emerges from tricuspid leaflets. observer variability for flow determined with the flow-convergence method. Jet proximal size interobserver variability. In the 40 patients studied, two observers, each blinded to the results obtained by the other, measured 48 regurgitant jet proxi. mal size in 16 patients. Statistics. The calculated regurgitant fraction (obtained with the Doppler-echo method) and the peak regurgitant flow, effective regurgitant orifice area, and momentum (calculated with the proximal flow-convergence technique) were compared with the jet proximal width by using linear regression analysis to determine correlation coefficient. RESULTS
Before this study, tricuspid stroke volume with the previously described Doppler m e t h o d was calculated in 14 patients w i t h o u t tricuspid or p u l m o n a r y regurgitation and compared with s i m u l t a n e o u s l y acquired t h e r m o d i l u t i o n data. For stroke volumes r a n g i n g from 41.5 to 125 cm 3 (71.8 +_ 21.4 cm), the difference (thermodilution - tricuspid, m e a n __ SD) in stroke volume was -3.4 _+ 8.9 am 3, with a n overall correlation of r = 0.93. In a n o t h e r group of 1 3 patients w i t h o u t tricuspid or p u l m o n a r y regurgitation, tricuspid and p u l m o n a r y stroke volume were cal-
culated. The difference ( t r i c u s p i d - p u l m o n a r y ) in stroke v o l u m e for the two m e t h o d s was -0.5 -+ 3.29 cm 3, with a n overall correlation of r = 0.95. For all cohort patients, m e a n jet proximal size ave r a g e d 6.7 + 2.4 m m (2.5 to 11.8 mm), p e a k flow r a t e 76 _+ 54 ml/sec (12 to 268 ml/sec) effective regurgitant orifice a r e a 27 _ 21 m m 2 (4 to 98 mm2), and m o m e n t u m 21717 _+ 15014 cm4/sec (23252 to 73432 cm4/sec. Good correlations were noted b e t w e e n p e a k flow r a t e (r = 0.80, p < 0.001; (Fig. 2), m o m e n t u m (r = 0.80,p < 0.001), and effective r e g u r g i t a n t orifice a r e a (r = 0.78, p < 0.001; Fig. 3), with proximal jet size m e a s u r e d in apical f o u r - c h a m b e r view in patients with free jets. M e a n j e t proximal size from t h r e e views h a d also good correlation w i t h p e a k flow r a t e (r = 0.75, p < 0.001), r e g u r g i t a n t fraction (r = 0.74,p < 0.001), m o m e n t u m (r = 0.74,p < 0.001), and effective r e g u r g i t a n t o r i f i c e a r e a ( r = 0 . 7 4 , p < 0.001). In patients with impinging jets, a g r e e m e n t was fair b e t w e e n effective r e g u r g i t a n t orifice (r = 0.65, p < 0.001; Fig. 4), p e a k flow r a t e (r = 0.62,p < 0.001), and m o m e n t u m (r = 0.62, p < 0.001), with m e a n j e t proximal size. Correlation b e t w e e n effective re-
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Fig. 3. Scatterplot shows correlation between tricuspid effective regurgitant orifice area (x axis) and jet proximal width in four-chamber view (y axis) for patients with free jets. gurgitant orifice area (r -- 0.64, p < 0.001), peak regurgitant flow (r = 0.61, p < 0.001), and momentum (r = 0.61, p < 0.001) was also fair, with maximum proximal jet size obtained from any plane. The interobserver variability for the jet proximal size method was 2.90% _+ 9.58%. DISCUSSION
The deleterious influence of persistent postsurgical tricuspid incompetence has been described in patients undergoing mitral surgery. 19, 20 Evaluation of
Fig. 4. Scatterplot shows correlation between tricuspid effective regurgitant orifice area (x axis) and mean jet proximal size (y axis) for patients with impinging jets. jets by color Doppler flow mapping has become the most common method of measuring regurgitation in clinical practice. Despite this, few studies 21, 22 of patients with tricuspid regurgitation have been published, probably because of the assumption that the results obtained in patients with mitral incompetence could be extrapolated without modification to the right side. Recently, good correlation has been found between proximal jet size of jets in patients with mitral and aortic regurgitation and flow parameters. 9-1° This proximal size of the jet as it emerges from the orifice has been shown to increase with the size of the regurgitant orifice 11 under clinical ranges of flow and driving pressures. It is easy to perform and has the advantage of being taken before the point of jet impingement. Furthermore, the high velocities at the jet origin are relatively independent of changes in instrument settings. 2s In the current study, we used as a gold standard the tricuspid regurgitant fraction obtained from the previously validated Doppler two-dimensional method. 12-14We also compared proximal tricuspid jet size with parameters derived from the recently validated flow convergence method, 5, 6 such as peak regurgitant flow, effective regurgitant orifice, and momentum. A particular p r o b l e m to studying the right heart is the lack of a standard echocardiographic view that allows a short-axis cut of the emerging regurgitant jet, which in part can explain differences with previous work. 9 In our case, we measured the tricuspid regurgitant jet proximal width as imaged on the apical four-chamber, para-
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sternal long right ventricular inflow, and parasternal short-axis views. Current study. In this study we found a good correlation between tricuspid regurgitant fraction and proximal jet size by using transthoracic color Doppler flow mapping in patients with free jets. Peak regurgitant flow, jet momentum, and effective regurgitant orifice area were also found to influence proximal jet size. This good predictability of the proximal jet size is not surprising because this measurement is closely related to regurgitant orifice area. In patients showing tricuspid impinging jets the correlation was worse, although still significant, presumably because some of them impact atrial structures immediately after their origin creating loss of momentum and morphologic distortion before they can be measured. The lack of surface echocardiographic cuts that permit short-axis visualization of tricuspid structures also contributes to this limitation. Limitations and future directions. A common limitation of all clinical studies of regurgitation is the lack of an accurate gold standard. We chose to use the Doppler-echo method that has been shown to correlate well with both roller pump and thermodilution stroke volume. 12, 15 In contrast, the angiographic grading method is highly subjective and affected by such variables as catheter position, rhythm disturbances, chamber size, forward flow, amount of dye injected, and radiogram penetration. These limitations are worse in the right side, where artifactual tricuspid incompetence makes this method practically unreliable. 15Additionally, the well-known problems in use of thermodilution in the presence of tricuspid regurgitation 24 result in an estimated error rate of 15% to 20% and consistent underestimation. Our measured difference in regurgitant stroke volume (tricuspid - pulmonary) (-0.5 +_ 3.3 cm 3) in 13 normal control patients without tricuspid regurgitation with the Doppler two-dimensional method and the previous study comparing the method with thermodilution in 14 normal patients with a difference (thermodilution- tricuspid, mean +_ SD) in stroke volume o f - 3 . 4 -+ 8.9 cm 3 demonstrates its applicability in the current analysis. Finite beam width and limited lateral resolution leads to an apparent increase in proximal jet dimension. The contraction of the jet as it enters the right atrium and the tissue-priority algorithm can act in opposite directions, u5-27 but good accuracy has been reported for stenotic jet size previously. ~s In any case, lateral resolution should produce similar effects among patients with comparable transducer frequencies and scanning depths.
Direct examination of digital color flow maps might overcome the limited video band width and subsequent image distortion and potentially allow three-dimensional reconstruction of the flow field to obtain the most accurate sections. High frame rate and high-resolution Doppler color flow mapping could help visualize temporal variation in proximal jet size. 29 In the present study, we correlated tricuspid proximal size with new parameters recently obtained from the proximal flow-convergence method such as peak regurgitant flow rate, effective regurgitant orifice area, and jet momentum, which have been previously found to influence jet areas in theoretic and in vitro studies. 3, 4 A potential error in calculating peak flow may result from the difficulty in localizing the regurgitant orifice because a small error in the measurements of the aliasing radius r will seriously affect the calculated flow rates. The clinical validation of a previously described automated algorithm, 3° which uses the full digital map of the proximal velocity field to localize the orifice center, may allow the proximal convergence calculation to be made routinely in clinical practice. REFERENCES
1. Omoto R, Yokote Y, Takamoto S, Kyo S, Ueda K, Asano H, Namekawa K, Kasai C, Kondo Y, Koyano A. The development of real time two-dimensional Doppler echocardiography and its clinical significance in acquired valvular diseases: with special reference to the evaluation of valvular regurgitation. Jpn Heart J 1984;25:325-40. 2. Sahn DJ. Instrumentation and physical factors related to visualizati0n of stenotic and regurgitant jets by Doppler color flow mapping. J Am Cell Cardiol 1988;12:1354-65. 3. Thomas JD, Liu CM, Flachskampf FA, O'Shea JP, DavidoffR, Weyman AE. Quantification of jet flow by momentum analysis: an in vitro color doppler flow study. Circulation 1990;81:247-59. 4. Cape EG, Yoganathan AP, Levine RA. A new method for noninvasive quantification of valvular regurgitation based on conservation of momentum: an in vitro validation. Circulation 1989;79:1343-53. 5. Bargiggia GS, Tronconi L, Sahn DJ, Recusani F, Raisaro A, De Servi S, Valdes-Cruz LM, Montemartini C. A new method for quantitation of mitral regurgitation based on color flow Doppler imaging of flow convergence proximal to regurgitaat orifice. Circulation 1991;84: 1481-9. 6. Rivera JM, Vandervoort P, Mele D, Weyman AE, Thomas J. Quantification of tricuspid regurgitation using the flow convergence method. A clinical study. AM HEARTJ 1994;127:1354-62. 7. Rivera JM, Mele D, Vandervoort P, Weyman AE, Thomas J. Physical factors influencing mitral regurgitation jet area in the clinical setting. Am J Cardiol 1994;74:515-6. 8. Chen C, Thomas JD, Anconina J, Harrigan P, Mueller L, Picard M, Levine RA, Weyman AE. Impact of impinging wall jet on color Doppler quantification of mitral regurgitation. Circulation 1991;84:712-20. 9. Mele D, Vandervoort PM, Palacios I, Rivera JM, Dinsmore R, Schwammental E, Marshall J, Weyman AE, Levine RA. Proximal jet size by Doppler color flow mapping predicts the severity of mitral regurgitation: clinical studies. Circulation 1995;91:746-54. 10. Perry GJ, Helmcke F, Nanda NC, Byard C, Sore B. Evaluation of aortic insufficiencyby Doppler color flow mapping. J Am Cell Cardio11987; 9:952-9. 11. Switzer DF, Yoganathan AP, Nanda NC, Woo Y-R, Ridgway AJ. Calibration of color Doppler flow mapping during extreme hemodynamic
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Value of proximal regurgitant jet size in tricuspid regurgitation J. Miguel Rivera, MD, PhD, a Peter Vandervoort, M D ? Donato Mele, MD, c Arthur Weyman, MD, d J a m e s D. Thomas, MD b Valencia, Spain, Cleveland, Ohio, Ferrara, Italy, and Boston, Mass.
Recent studies have shown good agreement between proximal regurgitant jet size obtained with transthoracic color flow mapping and regurgitant fraction in patients with mitral regurgitation. To evaluate this in patients with tricuspid regurgitation, we analyzed 40 patients in sinus rhythm, 16 with free jets and 24 with impinging jets, comparing proximal jet size (millimeters) with parameters derived from the Doppler two-dimensional echocardiographic method (regurgitant fraction) and the flow-convergence method (peak flow rate, effective regurgitant orifice area, and momentum). Good agreement was noted between peak flow rate (r= 0.80, p < 0.001), momentum (r= 0.80, p < 0.001), and effective regurgitant orifice area (r = 0.78, p < 0.001), with proximal jet size measured in the apical four-chamber view in patients with free jets. The average of jet proximal size in three planes also had good correlation with peak flow rate (r= 0.75, p < 0.001), regurgitant fraction, momentum, and effective regurgitant orifice area (r= 0.74, p < 0.001). In patients with impinging jets, agreement was fair between effective regurgitant orifice (r=0.65, p<0.001), peak flow rate (0.65, p < 0.001), and momentum (r= 0.62, p < 0.001) with mean jet proximal size. Jet proximal size obtained with transthoracic color flow mapping is a good semiquantitative tool for measuring tricuspid regurgitation in free jets that correlates well with established measures of the severity and with new parameters available from analysis of the proximal acceleration field. In patients with eccentrically directed wall jets, the correlation weakens but still appears clinically significant. (AM HEARTJ 1996;131:742-7.)
The arrival of color Doppler flow mapping has significantly improved the noninvasive evaluation of patients with valvular incompetence. 1 Visualization From aCentro de Investigacion Cardiocirculatoria, Hospital La Fe, Valencia; the bCardiology Department, Cleveland Clinic Foundation; the c Cardiology Department, Ospedale Civile, Ferrara; and the dCardiology Department, Massachusetts General Hospital and Harvard Medical School, Boston. Received for publication July 18, 1995; accepted Sept. 1, 1995. Reprint requests: J. Miguel R~vera, MD, PhD, c/Periodista Badia 11, pt 1, Valencia 46010, Spain. Copyright © 1996 by Mosby-Year Book, Inc. 0002-8703/96/$5.00 + 0 4/1/70063
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of jet area allows useful simultaneous semiquantitative grading of regurgitation, which permits immediate therapeutical decisions. Despite known limitations, 2 visual assessment has become the most common method used in daily clinical practice. Nevertheless, it has been shown that jet size correlates only weekly with regurgitant flow. Recently described quantitative parameters (peak flow rate, momentum, and effective regurgitant orifice area) have been found to influence jet areas in theoretic and in vitro studies 3, 4 and are now easily obtainable clinically from the proximal flow-convergence method. 5"7 Furthermore, in patient s with impinging jets, the correlation between jet dimensions and all these factors is poor. s Recently good agreement between proximal regurgitant jet size as imaged with transthoracic Doppler echocardiography and regurgitant flow has been described in patients with mitral and aortic insufficiency. 9, 10 This proximal dimension of the jet as it emerges from the orifice has been shown to increase with the size of the regurgitant orifice under clinical ranges of flow and driving pressures 11 and has the advantage of being measured before the point of impingement and being easy to perform. However, this method has not been tested in tricuspid regurgitation. The purpose of this study, therefore, was to evaluate the predictive value of proximal jet measurement when compared with regurgitant fraction and identify physical factors that influence its size in patients with tricuspid regurgitation. METHODS
Patients were studied by one research technician and were screened for the following selection criteria: (1) the presence of tricuspid regurgitation in the color Doppler display; (2) the presence of a proximal flow-convergence region on the color Doppler display at the ventricular surface of the tricuspid leaflets in at least one view obtained from a surface standardized-scanning plane; (3) availabil-
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ity of high-quality, two-dimensional images and Doppler tracings to allow accurate tricuspid and pulmonary flow calculations with the Doppler/two-dimensional echocardiographic method. 1214 Patients with tricuspid stenosis, accompanying pulmonary valve disease, or intracardiac shunt flow were excluded. Forty patients met the criteria for the study (22 women and 18 men) with a mean age of 66 _+ 15 years (age range 34 to 89 years). All 40 patients were in sinus rhythm at the time of the study. The underlying cardiac diseases included ischemic heart disease in 20 patients, mitral valve prolapse in 3, mitral rheumatic heart disease in 11, pericardial effusion in 2, and absence of detectable morphologic lesions in 4.
Echocardiographic data. All two-dimensional, pulsed, and color Doppler flow data were obtained as part of the routine echocardiographic evaluation. Commercially available Doppler echocardiography machines (Hewlett-Packard 77020A or Sonos 1000, Andover, Mass.), equipped with a standard 2.5 MHz transducer were used for the study. All images and spectral flow profiles were recorded on halfinch videotape for off-line analysis. Color Doppler images for analysis of the proximal flow convergence were obtained in parasternal long right ventricular inflow, apical four-chamber and parasternal shortaxis views at pulse repetition frequencies of 3.9 kHz to 4.8 kHz. The typical Nyquist velocity was 58 cm/sec at a scanning depth of 16 cm. Each color Doppler examination was performed with the narrowest sector angle possible (30 degrees) to maximize the color flow imaging frame rate (15 to 17 Hz). Data analysis. All M-mode tracings, two-dimensional images, Doppler spectra, and color Doppler images were analyzed off-line with a computer analysis system (Sony SUM 1010). All measurements were averaged at least over three cardiac cycles except for the radius measuremerit of the proximal flow convergence, as is discussed below. Doppler two-dimensional echocardiography. The overall approach to the pulsed Doppler quantification of tricuspid regurgitation has been previously detailed. With the method of Meijboom et al. 12 for calculating the tricuspid valve forward flow (VTv), the tricuspid valve flow area was determined from an apical four-chamber view. The tricuspid forward flow was determined as the product of tricuspid inflow time--velocity integral, diastolic tricuspid orifice area, and heart rate divided by cos 0. In our study, cos 0 range was 0.85 to I (0.93 -+ 0.04). Pulmonary forward flow was obtained by the method described by Goldberg et a]. 13 and Valdes-Cruz et al.14 Transpulmonary forward flow (Vpv) was calculated from the product of systolic pulmonary area, pulmonary timevelocity integral, and heart rate. In the absence of pulmonary regurgitation or abnormal shunt flow, the tricuspid regurgitant stroke volume (SV) was given as the difference between tricuspid inflow and pulmonary outflow. 13, 15 Multiplying regurgitant stroke volume (SV) by heart rate (HR) yields regurgitant flow rate Q (cm3/min), with reg~rgitant fraction obtained by SV/V~.
Rivera et al. 743 Proximalflow-convergence calculation. With the method previously described, 6 from the apical four-chamber or parasternal right ventricular-inflow view, the ventricular surface of the tricuspid valve leaflets was carefully scanned for the presence of a flow-convergence region proximal to the site of regurgitation. In this study the aliasing velocity was typically set to 19 cm/sec. By means of the proximal flow-convergence method, maximal regurgitant flow rate (Qp) was calculated as the product of the largest proximal isovelocity surface area multiplied by the velocity at that surface. Assuming simple hemispheric symmetry of the converging flow field, the proximal isovelocity surface area can be calculated as 2~r 2, where r is the radius measured from the first color alias to the regurgitant orifice. Previous work in our laboratory has demonstrated a predictable, systematic underestimation of flow rate as a result of flattening of the isovelocity contours close to the orifice, an error that can be corrected by multiplying the calculated flow rate by vp/(Vp - Va), where Vpis the peak orifice velocity (from continuous-wave Doppler) and va is the aliasing velocity of interest.16 Because this error is particularly troublesome for right-sided regurgitant lesions where Va is a significant proportion Of Vp, we applied this correction factor to our data. Similarly, we have shown that the proximal convergence zone may be distorted by the global geometry in which the orifice lies. 17, ~s A correction that has been validated is to multiply 2~ by d180, where a is the angle subtended by the valve leaflets. A similar correction ~kas applied here: was measured with a protractor from still-frame printouts of the valve image taken in the apical four-chamber view. Combining these corrections for local and global geometric factors yielded the following overall equation for peak instantaneous regurgitant flow rate (cm3/sec) Qp = 2~r2Va • [ ~
V
c~
]" (1-~).
Effective regurgitant orifice area (ROA) can then easily be obtained by ROA = QP.
Vp
Jet momentum was calculated at the regurgitant orifice level as the product of peak regurgitant flow times the relocity at that level. 3, 7 The flow through the orifice was calculated by using the proximal flow-convergence method, and the velocity was obtained from the continuous wave. Jet proximal size. For jet proximal size, distance was measured as close as possible to the regurgitant orifice and was traced with a light pen (Fig. 1). Jets were classified into two types: free and walk s Proximal jet size was measured in apical four-chamber and parasternal long right ventricular inflow and short-axis views. Maximum jet size in the three planes and average of three planes were also measured.
Reproducibility of measurements Proximal flow-convergence method, interobserver variability. In a previous study, 6 we calculated the inter-
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Fig. 1. Color Doppler echo view of patient with tricuspid regurgitation shows measurement of proximal jet width (arrows) as it emerges from tricuspid leaflets. observer variability for flow determined with the flow-convergence method. Jet proximal size interobserver variability. In the 40 patients studied, two observers, each blinded to the results obtained by the other, measured 48 regurgitant jet proxi. mal size in 16 patients. Statistics. The calculated regurgitant fraction (obtained with the Doppler-echo method) and the peak regurgitant flow, effective regurgitant orifice area, and momentum (calculated with the proximal flow-convergence technique) were compared with the jet proximal width by using linear regression analysis to determine correlation coefficient. RESULTS
Before this study, tricuspid stroke volume with the previously described Doppler m e t h o d was calculated in 14 patients w i t h o u t tricuspid or p u l m o n a r y regurgitation and compared with s i m u l t a n e o u s l y acquired t h e r m o d i l u t i o n data. For stroke volumes r a n g i n g from 41.5 to 125 cm 3 (71.8 +_ 21.4 cm), the difference (thermodilution - tricuspid, m e a n __ SD) in stroke volume was -3.4 _+ 8.9 am 3, with a n overall correlation of r = 0.93. In a n o t h e r group of 1 3 patients w i t h o u t tricuspid or p u l m o n a r y regurgitation, tricuspid and p u l m o n a r y stroke volume were cal-
culated. The difference ( t r i c u s p i d - p u l m o n a r y ) in stroke v o l u m e for the two m e t h o d s was -0.5 -+ 3.29 cm 3, with a n overall correlation of r = 0.95. For all cohort patients, m e a n jet proximal size ave r a g e d 6.7 + 2.4 m m (2.5 to 11.8 mm), p e a k flow r a t e 76 _+ 54 ml/sec (12 to 268 ml/sec) effective regurgitant orifice a r e a 27 _ 21 m m 2 (4 to 98 mm2), and m o m e n t u m 21717 _+ 15014 cm4/sec (23252 to 73432 cm4/sec. Good correlations were noted b e t w e e n p e a k flow r a t e (r = 0.80, p < 0.001; (Fig. 2), m o m e n t u m (r = 0.80,p < 0.001), and effective r e g u r g i t a n t orifice a r e a (r = 0.78, p < 0.001; Fig. 3), with proximal jet size m e a s u r e d in apical f o u r - c h a m b e r view in patients with free jets. M e a n j e t proximal size from t h r e e views h a d also good correlation w i t h p e a k flow r a t e (r = 0.75, p < 0.001), r e g u r g i t a n t fraction (r = 0.74,p < 0.001), m o m e n t u m (r = 0.74,p < 0.001), and effective r e g u r g i t a n t o r i f i c e a r e a ( r = 0 . 7 4 , p < 0.001). In patients with impinging jets, a g r e e m e n t was fair b e t w e e n effective r e g u r g i t a n t orifice (r = 0.65, p < 0.001; Fig. 4), p e a k flow r a t e (r = 0.62,p < 0.001), and m o m e n t u m (r = 0.62, p < 0.001), with m e a n j e t proximal size. Correlation b e t w e e n effective re-
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20
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150
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Fig. 2. Scatterplot shows correlation between tricuspid peak flow rate (x axis) and jet proximal width in fourchamber view (y axis) for patients with free jets.
20
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Peak Flow Rate [cm3/s]
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Fig. 3. Scatterplot shows correlation between tricuspid effective regurgitant orifice area (x axis) and jet proximal width in four-chamber view (y axis) for patients with free jets. gurgitant orifice area (r -- 0.64, p < 0.001), peak regurgitant flow (r = 0.61, p < 0.001), and momentum (r = 0.61, p < 0.001) was also fair, with maximum proximal jet size obtained from any plane. The interobserver variability for the jet proximal size method was 2.90% _+ 9.58%. DISCUSSION
The deleterious influence of persistent postsurgical tricuspid incompetence has been described in patients undergoing mitral surgery. 19, 20 Evaluation of
Fig. 4. Scatterplot shows correlation between tricuspid effective regurgitant orifice area (x axis) and mean jet proximal size (y axis) for patients with impinging jets. jets by color Doppler flow mapping has become the most common method of measuring regurgitation in clinical practice. Despite this, few studies 21, 22 of patients with tricuspid regurgitation have been published, probably because of the assumption that the results obtained in patients with mitral incompetence could be extrapolated without modification to the right side. Recently, good correlation has been found between proximal jet size of jets in patients with mitral and aortic regurgitation and flow parameters. 9-1° This proximal size of the jet as it emerges from the orifice has been shown to increase with the size of the regurgitant orifice 11 under clinical ranges of flow and driving pressures. It is easy to perform and has the advantage of being taken before the point of jet impingement. Furthermore, the high velocities at the jet origin are relatively independent of changes in instrument settings. 2s In the current study, we used as a gold standard the tricuspid regurgitant fraction obtained from the previously validated Doppler two-dimensional method. 12-14We also compared proximal tricuspid jet size with parameters derived from the recently validated flow convergence method, 5, 6 such as peak regurgitant flow, effective regurgitant orifice, and momentum. A particular p r o b l e m to studying the right heart is the lack of a standard echocardiographic view that allows a short-axis cut of the emerging regurgitant jet, which in part can explain differences with previous work. 9 In our case, we measured the tricuspid regurgitant jet proximal width as imaged on the apical four-chamber, para-
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sternal long right ventricular inflow, and parasternal short-axis views. Current study. In this study we found a good correlation between tricuspid regurgitant fraction and proximal jet size by using transthoracic color Doppler flow mapping in patients with free jets. Peak regurgitant flow, jet momentum, and effective regurgitant orifice area were also found to influence proximal jet size. This good predictability of the proximal jet size is not surprising because this measurement is closely related to regurgitant orifice area. In patients showing tricuspid impinging jets the correlation was worse, although still significant, presumably because some of them impact atrial structures immediately after their origin creating loss of momentum and morphologic distortion before they can be measured. The lack of surface echocardiographic cuts that permit short-axis visualization of tricuspid structures also contributes to this limitation. Limitations and future directions. A common limitation of all clinical studies of regurgitation is the lack of an accurate gold standard. We chose to use the Doppler-echo method that has been shown to correlate well with both roller pump and thermodilution stroke volume. 12, 15 In contrast, the angiographic grading method is highly subjective and affected by such variables as catheter position, rhythm disturbances, chamber size, forward flow, amount of dye injected, and radiogram penetration. These limitations are worse in the right side, where artifactual tricuspid incompetence makes this method practically unreliable. 15Additionally, the well-known problems in use of thermodilution in the presence of tricuspid regurgitation 24 result in an estimated error rate of 15% to 20% and consistent underestimation. Our measured difference in regurgitant stroke volume (tricuspid - pulmonary) (-0.5 +_ 3.3 cm 3) in 13 normal control patients without tricuspid regurgitation with the Doppler two-dimensional method and the previous study comparing the method with thermodilution in 14 normal patients with a difference (thermodilution- tricuspid, mean +_ SD) in stroke volume o f - 3 . 4 -+ 8.9 cm 3 demonstrates its applicability in the current analysis. Finite beam width and limited lateral resolution leads to an apparent increase in proximal jet dimension. The contraction of the jet as it enters the right atrium and the tissue-priority algorithm can act in opposite directions, u5-27 but good accuracy has been reported for stenotic jet size previously. ~s In any case, lateral resolution should produce similar effects among patients with comparable transducer frequencies and scanning depths.
Direct examination of digital color flow maps might overcome the limited video band width and subsequent image distortion and potentially allow three-dimensional reconstruction of the flow field to obtain the most accurate sections. High frame rate and high-resolution Doppler color flow mapping could help visualize temporal variation in proximal jet size. 29 In the present study, we correlated tricuspid proximal size with new parameters recently obtained from the proximal flow-convergence method such as peak regurgitant flow rate, effective regurgitant orifice area, and jet momentum, which have been previously found to influence jet areas in theoretic and in vitro studies. 3, 4 A potential error in calculating peak flow may result from the difficulty in localizing the regurgitant orifice because a small error in the measurements of the aliasing radius r will seriously affect the calculated flow rates. The clinical validation of a previously described automated algorithm, 3° which uses the full digital map of the proximal velocity field to localize the orifice center, may allow the proximal convergence calculation to be made routinely in clinical practice. REFERENCES
1. Omoto R, Yokote Y, Takamoto S, Kyo S, Ueda K, Asano H, Namekawa K, Kasai C, Kondo Y, Koyano A. The development of real time two-dimensional Doppler echocardiography and its clinical significance in acquired valvular diseases: with special reference to the evaluation of valvular regurgitation. Jpn Heart J 1984;25:325-40. 2. Sahn DJ. Instrumentation and physical factors related to visualizati0n of stenotic and regurgitant jets by Doppler color flow mapping. J Am Cell Cardiol 1988;12:1354-65. 3. Thomas JD, Liu CM, Flachskampf FA, O'Shea JP, DavidoffR, Weyman AE. Quantification of jet flow by momentum analysis: an in vitro color doppler flow study. Circulation 1990;81:247-59. 4. Cape EG, Yoganathan AP, Levine RA. A new method for noninvasive quantification of valvular regurgitation based on conservation of momentum: an in vitro validation. Circulation 1989;79:1343-53. 5. Bargiggia GS, Tronconi L, Sahn DJ, Recusani F, Raisaro A, De Servi S, Valdes-Cruz LM, Montemartini C. A new method for quantitation of mitral regurgitation based on color flow Doppler imaging of flow convergence proximal to regurgitaat orifice. Circulation 1991;84: 1481-9. 6. Rivera JM, Vandervoort P, Mele D, Weyman AE, Thomas J. Quantification of tricuspid regurgitation using the flow convergence method. A clinical study. AM HEARTJ 1994;127:1354-62. 7. Rivera JM, Mele D, Vandervoort P, Weyman AE, Thomas J. Physical factors influencing mitral regurgitation jet area in the clinical setting. Am J Cardiol 1994;74:515-6. 8. Chen C, Thomas JD, Anconina J, Harrigan P, Mueller L, Picard M, Levine RA, Weyman AE. Impact of impinging wall jet on color Doppler quantification of mitral regurgitation. Circulation 1991;84:712-20. 9. Mele D, Vandervoort PM, Palacios I, Rivera JM, Dinsmore R, Schwammental E, Marshall J, Weyman AE, Levine RA. Proximal jet size by Doppler color flow mapping predicts the severity of mitral regurgitation: clinical studies. Circulation 1995;91:746-54. 10. Perry GJ, Helmcke F, Nanda NC, Byard C, Sore B. Evaluation of aortic insufficiencyby Doppler color flow mapping. J Am Cell Cardio11987; 9:952-9. 11. Switzer DF, Yoganathan AP, Nanda NC, Woo Y-R, Ridgway AJ. Calibration of color Doppler flow mapping during extreme hemodynamic
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