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Perioperative outcomes in reoperative cardiac surgery guided by cardiac multidetector computed tomographic angiography
Imaging and Diagnostic Testing
Perioperative outcomes in reoperative cardiac surgery guided by cardiac multidetector computed tomographic angiography Gabriel Maluenda, MD, Matthew A. Goldstein, MD, Gilles Lemesle, MD, Gaby Weissman, MD, Guy Weigold, MD, Marc J. Landsman, BS, Peter C. Hill, MD, Francisco Pita, MD, Paul J. Corso, MD, Steven W. Boyce, MD, Augusto D. Pichard, MD, Ron Waksman, MD, and Allen J. Taylor, MD Washington, DC
Background Preoperative evaluation with contrast-enhanced multidetector computed tomographic angiography (MDCTA) is considered an “appropriate” indication based on expert consensus. We aimed to evaluate how the presurgical evaluation with MDCTA impacts the outcomes after reoperative cardiac surgery (RCS). Methods
We retrospectively studied 364 patients undergoing RCS between 2004 and 2008, including 137 referred for MDCTA. High-risk CT findings were defined as the presence of right ventricle or aorta b10 mm from the sternum or a bypass graft b10 mm from the sternum crossing the midline. The primary clinical end point was the composite of perioperative death, myocardial infarction (MI), stoke, and hemorrhage-related reoperation. Secondary end points included surgical procedural variables and the perioperative volume of bleeding and of red blood cell (RBC) transfusion.
Results Baseline clinical characteristics were similar between the 2 groups. Individuals referred for MDCTA showed a trend toward a lower incidence of the composite primary end point (17.5% vs 24.2%, P = .13), primarily related to a significantly lower incidence of perioperative MI (0% vs 5.7%, P = .002). Multidetector computed tomographic angiography was also associated with shorter perfusion (90 vs 110 minutes, P = .002), cross clamp time (63 vs 75 minutes, P = .003), and total time in intensive care unit (103 vs 148 hours, P = .04), and a lower volume of postoperative RBC transfusion (627 vs 824 mL, P = .09). These differences remained significant after adjustment for the Society of Thoracic Surgeons score and the performing surgeon. Conclusion
The use of MDCTA before RCS was associated with shorter perfusion and cross clamp time, shorter intensive care unit stays, and less frequent perioperative MI. (Am Heart J 2010;159:301-6.)
Reoperative cardiac surgery (RCS) carries a high mortality and morbidity1-5 due to increased technical difficulty as well as a higher prevalence and severity of coronary artery disease and comorbidities.2-7 The primary technical concern during surgical reentry is the presence of cardiovascular structures immediately beneath the sternum that pose a threat for injury. Of particular concern is the potential for injury of vital structures such as the right ventricle (RV), aorta, and coronary bypass grafts with catastrophic consequences.7,8 Thus, RCS represents a challenging situation for the cardiac surgical team where methods to reduce
From the Noninvasive Cardiovascular Imaging, Department of Medicine/Cardiology, Washington Hospital Center, and Cardiac Surgery Department, Washington Hospital Center, Washington, DC. Submitted August 27, 2009; accepted November 10, 2009. Reprint requests: Allen J. Taylor, MD, Department of Medicine, Section of Cardiology, 110 Irving St, NW, Room 1E12, Washington, DC 20010-2975. E-mail: [email protected] 0002-8703/$ - see front matter © 2010, Mosby, Inc. All rights reserved. doi:10.1016/j.ahj.2009.11.005
the occurrence of serious but preventable complications achieve paramount importance. One promising method to mitigate the risk of surgical reentry during RCS is through the use of contrastenhanced multidetector computed tomographic angiography (MDCTA). This technique comprehensively evaluates the structures of interest to the surgeon, including the chest wall, mediastinal structures, coronary bypass grafts, and their relationship to each other.9,10 The multisociety cardiac CT appropriateness criteria published in 2006 defined the use of MDCTA before repeat coronary surgery as an “appropriate” indication based upon expert consensus.11 However, there is little data to support this recommendation, with only a single center reporting on the frequency of high risk findings and possible changes to the surgical approach.12 Outcome data are needed to either support or refute the appropriateness criteria recommendation and inform clinical practice. The hypothesis of this retrospective study was that a MDCTA “roadmap” of substernal anatomy could guide the surgical approach and minimize the risk of injury upon surgical reentry. On the basis this potential benefit
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Figure 1
A, Axial view of MDCTA of the chest showing the absence of high-risk findings (LV, Left ventricle; RV, right ventricle; ST, sternum). B, Sagittal view of MDCTA of the thorax demonstrating the normal relationship between cardiac structures and the sternum (AA, Ascending aorta; PA, pulmonary artery; RA, right atrium; RV, right ventricle, ST, sternum).
of MDCTA to improve the safety of RCS, our center began performing MDCTA in 2004 for this indication. This study examines the relationship between presurgical evaluation with MDCTA and perioperative outcomes in patients undergoing RCS.
Methods and materials Study population We used the Society of Thoracic Surgeons (STS) database13 to identify patients who underwent RCS (n = 364) at the Washington Hospital Center (Washington, DC) between January 1, 2004, and December 31, 2008. Among these surgical patients, 137 were clinically referred for preoperative MDCTA, and 227 patients underwent RCS without MDCTA during the same period. All patients gave written consent for the proposed surgery, and this retrospective study was conducted under institutional review board approval.
Follow-up Baseline demographics, procedural data, and perioperative outcomes were recorded at the time of the procedure and entered in a computerized database by a dedicated datacoordinating center. All in-hospital adverse events were source documented and entered with standardized criteria in a computerized database by research nurses (exclusive of the nurses who performed the data collection). A separate team of research assistants collected follow-up clinical data by telephone questionnaire 30 days after discharge from the hospital, and events were similarly reconciled after reviewing the original source documents.
End points The primary end point prespecified by the study protocol was the composite rate of perioperative complications (myocardial infarction [MI], stroke, and hemorrhage-related reoperation) and operative death. The secondary end points included intraoperative hemodynamic outcomes (perfusion time and cross clamp time), total intensive care unit (ICU) time, the amount of perioperative bleeding and red blood cell (RBC) transfusions, and the rate of changes to the standard surgical approach, including the use of a nonmidline incision and a cannulation method excluding the aorta.
Multidetector computed tomographic angiography data acquisition and collection Cardiothoracic MDCTA was performed with 16-, 64-, or 256detector Brilliance scanners (Philips Medical Systems Inc, Cleveland, OH). Technical parameters were specific to the scanner generation used; however, all studies were performed with helical scanning with retrospective electrocardiographic gating and radiation dose modulation with ≤1-mm slice thickness and ≤90-mL isosmolar contrast. β-Blockers were used as needed to achieve a heart rate b65 beat/min. Acquisition was performed during a 10- to 20-second breathhold. Reconstructions included thin-slice (≤1 mm) reconstructions at middiastole and thick slice (2 mm) reconstructions at 10% intervals throughout the cardiac cycle for the cine-loop display. Scans were clinically interpreted by 1 of 4 experienced cardiac CT interpreters. High-risk findings on preoperative MDCTA were defined according to previously published criteria, with representative examples shown in Figures 1 to 3.12 These findings included (1) RV or aorta b1 cm below the sternal
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upper limit.14 Postoperative stroke was defined as any new major (type II) neurologic deficit presenting in-hospital and persisting for N72 hours.15 Hemorrhage-related reoperation was defined as urgent reexploration driven by bleeding or cardiac tamponade. Perfusion time was defined as the total of cardiopulmonary bypass and/or coronary perfusion assist minutes. Cross clamp time indicates the total number of minutes the aorta is completely cross clamped during bypass. Changes to the standard surgical approach were defined as the use of an incision avoiding the midline and/or a cannulation method for cardiopulmonary bypass excluding the aorta.
Statistical analysis
Axial view of MDCTA of the thorax showing a directly apposed free wall of the RV to the posterior aspect of the sternum, finding pointed by the arrow (LA, Left atrium; LV, left ventricle; RV, right ventricle; ST, sternum).
midline, (2) bypass grafts that crossed the midline within 1 cm posterior to the sternum, or (3) any cardiovascular structures adherent to the sternum as identified using cine-image display. Data were extracted from the electronic medical record based upon a standard scan interpretation methodology used at our institution.
Operative technique Standard anesthesia and surgical techniques, extracorporeal circulation, and myocardial protection methods were used for all patients. Patients underwent anticoagulation using 3 mg/kg of heparin sulfate to maintain an activated clotting time of ≥480 seconds. The institutional standardized protocol for blood product transfusion and for blood salvage was used. Aprotinin was not routinely administered. Desmopressin acetate was used in patients with renal insufficiency. Crystalloid solutions were used for volume replacement. All patients were rewarmed to 36°C before discontinuing the cardiopulmonary bypass. Normothermia was maintained during the intraoperative period after cardiopulmonary bypass. The clinical practice guidelines recommended blood transfusion at a hematocrit of b22% for patients b65 years old or b24% for patients ≥65 years old.
Definitions Operative mortality was defined as death occurring during the initial hospitalization or within 30 days after surgery. Perioperative MI was defined as new Q waves in 2 contiguous electrocardiogram leads or new left bundle branch block and elevation of the MB fraction of creatine kinase N5 times the
Continuous variables were expressed as mean ± SD. Categorical variables were expressed as absolute number and percentages. Baseline characteristics between the 2 groups—those with and without preoperative MDCTA—were compared by using the χ2 test or the Fisher test for categorical variables and the Student unpaired t test for continuous variables as appropriate. Multivariable logistic regression analysis controlling for differences in baseline covariates, weighted by the predicted risk of mortality and morbidity using the STS risk score16 and the primary surgeon were used to determine the independent relationship between MDCTA and perioperative outcomes after RCS. All statistical analysis was performed using SPSS version 16.0 (SPSS Inc, Chicago, IL). Statistical significance was assumed at P b .05. No extramural funding was used to support this work. The authors are solely responsible for the design and conduct of this study; all study analyses, and the drafting and editing of the article and its final contents.
Results The baseline clinical characteristics of the patients with and without MDCTA before RCS are shown in Table I. Both groups were similar in the clinical characteristics. As expected, there was a high prevalence of comorbidities, reflected by a high STS score for morbidity or mortality (27%). The MDCTA group had a higher prevalence of previous stroke (33.6% vs 20.7%) and higher prevalence of previous percutaneous coronary intervention (55.5% vs 41.0%). Most operations (53%) were isolated reoperative coronary artery bypass graft (CABG), 24% of the patients underwent valve surgery only, 20% had a combined CABG-valve procedure, and 3% of the cases had aortic aneurysm repair. Elective operations were performed in 51%, whereas 44% were urgent and 5% emergent, as defined by the STS. Perioperative complications including death (11%), MI (3.6%), stroke (4.1%), and hemorrhage-related reoperation (7.4%) are shown for the study groups in Table II. Patients referred for cardiac MDCTA showed a trend toward a lower incidence of the composite primary end point of death-MI-stroke-hemorrhage–related reoperation (17.5% vs 24.2%, P = .13), which was driven primary by a significantly lower incidence of perioperative MI in the MDCTA group (0% vs 5.7%, P = .002). All these
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Figure 3
A, Axial view of MDCTA of the thorax showing an adherent saphenous aortocoronary graft to the posterior aspect of the sternum at the midline, finding pointed by the arrow (AR, Aortic root; DA, descending aorta; LA, left atrium; LL, left lung; RV, right ventricle; RL, right lung; ST, sternum). B, Sagittal view of MDCTA of the chest demonstrating the same adherent saphenous aortocoronary graft to the posterior surface of the sternum at the midline level, remarked by the arrow.
Table I. Baseline clinical characteristics
Age, y ± SD Male, n (%) Diabetes, n (%) Hypertension, n (%) Previous smoking, n (%) Hypercholesterolemia, n (%) BMI, kg/m2 ± SD Family history of CAD, n (%) History of MI, n (%) History of PCI, n (%) History of CHF, n (%) History of stroke, n (%) History of PVD, n (%) History of CLD, n (%) Serum creatinine level, mg/dL Left ventricular EF, % ± SD STS risk score of death and morbidity, ± SD
Table II. Postoperative outcomes regarding the use of preoperative MDCTA
MDCTA (n = 137)
No MDCTA (n = 227)
P
68.3 ± 9.2 101 (73.5) 48 (35.0) 119 (86.9) 81 (59.1) 125 (91.2) 28.6 ± 4.9 77 (57.0) 62 (45.6) 76 (55.5) 44 (32.1) 46 (33.6) 29 (21.3) 33 (24.1) 1.38 ± 1.32 45.4 ± 10.5 0.258 ± 0.161
68.1 ± 9.6 176 (77.5) 102 (44.9) 196 (86.3) 136 (60.4) 202 (89.0) 28.3 ± 5.2 129 (59.7) 118 (54.6) 93 (41.0) 76 (33.6) 47 (20.7) 54 (24.0) 42 (18.6) 1.58 ± 1.72 43.1 ± 11.7 0.273 ± 0.188
.78 .41 .063 .89 .80 .49 .62 .62 .098 .007 .77 .006 .56 .21 .24 .053 .49
BMI, Body mass index; CAD, coronary artery disease; MI, myocardial infarction; PCI, percutaneous coronary intervention; CHF, congestive heart failure; PVD, peripheral vascular disease; CLD, chronic lung disease; EF, ejection fraction; SD, standard deviation.
differences remained statistically significant after adjustment for the STS score and the performing surgeon (OR 0.50, 95% CI 0.25-1.0, P = .05). Preoperative MDCTA was associated with shorter perfusion (90 vs 110 minutes, P = .002) and cross clamp time (63 vs 75 minutes, P = .003), reduced total time in the ICU (103 vs 148 hours, P = .042), and a trend toward lower volume of postoperative of RBC transfusions (627 vs 824 mL, P = .09).
Death, n (%) Myocardial infarction, n (%) Stroke, n (%) Urgent reoperation, n (%) Composite primary end point, n (%) Perfusion time, min ± SD Cross clamp time, min ± SD Total time in ICU, h ± SD Intraoperative estimated blood loss, mL ± SD Intraoperative RBC transfusion, mL ± SD Postoperative RBC transfusion, mL ± SD Intraoperative and postoperative RBC transfusion, mL ± SD No middle incision, n (%) Cannulation excluding aorta, n (%)
MDCTA (n = 137)
No MDCTA (n = 227)
P
15 (10.9) 0 5 (3.6) 13 (9.5) 24 (17.5)
25 (11.0) 13 (5.7) 10 (4.4) 14 (6.2) 55 (24.2)
.99 .002 .79 .24 .13
110.1 ± 63.8 74.8 ± 38.0 148.0 ± 225.6 643.4 ± 375.9
.002 .003 .042 .61
90.1 62.6 103.0 624.1
± 34.2 ± 23.7 ± 162.0 ± 313.4
611.3 ± 545.6 627.0 ± 823.7
585.9 ± 596.6 .66
1233.7 ± 1083.9
824.1 ± 1175.8 1406.4 ± 1473.5
3 (2.2) 5 (3.6)
9 (4.0) 10 (4.4)
.09 .24
.55 .79
ICU, Intensive care unit; RBC, red blood cell; SD, standard deviation.
Among the subgroup that underwent MDCTA, the presence of a high-risk RV finding was associated with a significantly higher volume of intraoperative estimated blood loss (P = .04), intraoperative RBC transfusions (P = .03), and the total amount of RBCs transfused during and after the surgery (P = .01) (Table III). The presence of
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Table III. Postoperative outcomes regarding the presence of high-risk findings RV at high risk
Perfusion time, min ± SD Cross clamp time, min ± SD Total time in ICU, h ± SD Intraoperative estimated blood loss, mL ± SD Intraoperative RBC transfusion, mL ± SD Intraoperative and postoperative RBC transfusion, mL ± SD No middle incision, n (%) Cannulation excluding aorta, n (%)
Graft at high risk
High risk (n = 104)
No high risk (n = 33)
P
High risk (n = 21)
No high risk (n = 116)
P
88.7 ± 31.5 61.8 ± 22.6 115.5 ± 160.7 654 ± 332 668 ± 555 1365.6 ± 1141.1 3 (1.9) 5 (4.8)
95.5 ± 44.3 66.1 ± 28.3 63.4 ± 162.0 529 ± 431 432 ± 477 818.2 ± 753.3 1 (3.0) 0
0.41 0.45 0.11 0.045 0.03 0.011 0.7 0.19
98.9 ± 39.0 65.4 ± 19.5 101.5 ± 89.3 678 ± 251 678 ± 475 1357 ± 673 1 (4.8) 4 (19)
88.3 ± 33.1 62.1 ± 24.5 103.2 ± 172.2 614 ± 323 599 ± 558 1211 ± 1143 2 (1.7) 1 (0.9)
.31 .26 .37 .82 .63 .09 .38 b.001
ICU, Intensive care unit; RBC, red blood cell; SD, standard deviation.
other high-risk findings, in particular bypass grafts crossing the midline near the sternum, were not associated with the occurrence of any adverse outcomes. However, changes to the standard surgical approach, in particular the adoption of an alternative cannulation method excluding the aorta, were associated with the presence of high-risk graft findings (P b .001) but not to other high-risk findings.
Discussion This study shows that the use of MDCTA before RCS was associated with less frequent perioperative MI, shorter operative hemodynamic times, shorter ICU stays, and trends toward lower volume of RBC transfusions after the surgery. Among potentially high-risk MDCTA findings, and in particular high-risk RV findings, we noted a higher risk of bleeding and RBC transfusion during and after the surgery. The higher risk of perioperative complications during RCS2-4 is multifactorial. Patient-related factors include a greater extent of the coronary artery disease and comorbidities.2,5,17,18 Technical factors include substernal structures at risk for injury during surgical reentry, more complex dissection with risk to coronary bypass grafts, and increased perioperative blood loss. Accordingly, our results are consistent with the concept that guidance of surgical reentry and dissection through preoperative MDCTA leads to improved outcomes including faster operative times, less risk for perioperative MI, lower rates of bleeding, and shorter ICU stays after the procedure. Our study identifies high-risk RV findings as a marker of potential bleeding complications. The lower incidence of perioperative MI among patients receiving MDCTA is notable and may have arisen through less manipulation of in situ bypass grafts. However, we urge caution in interpretation of this finding within a single component of the composite primary end point. The use of preoperative MDCTA has been previously reported. Two small reports described the potential benefit of the 16-slice MDCTA for modification of the
surgical plan.10,19 In addition, Kamdar et al12 published a series of 167 patients with prior CABG who underwent RCS with preoperative MDCTA evaluation. They showed that routine use of MDCTA before RCS detects high-risk findings that were strongly associated with the adoption of preventive surgical strategies. However, they did not report any relationship to perioperative outcomes. Indeed, we also found an association between the presences of high-risk graft findings and the adoption of an alternative cannulation method but importantly extend these results to include perioperative outcomes. The 2006 multisociety appropriateness criteria for cardiac CT identified the use of CT before RCS as an “appropriate” indication.11 Guided by expert opinion, subsequent evidence, including the present study, appears to support this recommendation. However, in the absence of a randomized controlled trial, definitive conclusions regarding the impact of preoperative MDCTA must be made with caution. Additional prospective data from surgical registries should be collected to confirm our results. Findings from this study could be used to inform the design and sample size for clinical trial planning. There are limitations to our study. This is a retrospective analysis centered on a prespecified end point using concurrent surgical populations. Although the study groups were well matched, the potential for confounding by unmeasured variables must be considered. We attempted to broadly adjust for potential differences among patients with and without preoperative MDCTA by adjusting for surgical risk using the well-validated STS risk score. The observed association of MDCTA with improved perioperative outcomes cannot be causally attributed to MDCTA alone. This analysis was underpowered to establish direct relationship between the presence of high-risk MDCTA findings and the frequency of changes to the standard surgical approach. However, during the study period, no patients were refused RCS based upon MDCTA findings. Moreover, the findings are consistent with the concept that MDCTA guidance aided the technical performance of the operation.
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In conclusion, the use of MDCTA before RCS was associated with improved perioperative outcomes including shorter operative times and ICU stays and less frequent perioperative MI. Among MDCTA findings, the presences of high-risk RV findings are associated with a higher amount of bleeding during and after the surgery.
11.
References 1. Salomon NW, Page US, Bigelow JC, et al. Reoperative coronary surgery. Comparative analysis of 6591 patients undergoing primary bypass and 508 patients undergoing reoperative coronary artery bypass. J Thorac Cardiovasc Surg 1990;100:250-9 [discussion 259-260]. 2. Weintraub WS, Jones EL, Craver JM, et al. In-hospital and long-term outcome after reoperative coronary artery bypass graft surgery. Circulation 1995;92:II50-7. 3. Yau TM, Borger MA, Weisel RD, et al. The changing pattern of reoperative coronary surgery: trends in 1230 consecutive reoperations. J Thorac Cardiovasc Surg 2000;120:156-63. 4. Rao V, Ivanov J, Weisel RD, et al. Predictors of low cardiac output syndrome after coronary artery bypass. J Thorac Cardiovasc Surg 1996;112:38-51. 5. Shapira I, Isakov A, Heller I, et al. Long-term follow-up after coronary artery bypass grafting reoperation. Chest 1999;115:1593-7. 6. van Eck FM, Noyez L, Verheugt FW, et al. Preoperative prediction of early mortality in redocoronary artery surgery. Eur J Cardiothorac Surg 2002;21:1031-6. 7. Dobell AR, Jain AK. Catastrophic hemorrhage during redo sternotomy. Ann Thorac Surg 1984;37:273-8. 8. van Eck FM, Noyez L, Verheugt FW, et al. Changing profile of patients undergoing redo-coronary artery surgery. Eur J Cardiothorac Surg 2002;21:205-11. 9. Schlosser T, Konorza T, Hunold P, et al. Noninvasive visualization of coronary artery bypass grafts using 16-detector row computed tomography. J Am Coll Cardiol 2004;44:1224-9. 10. Gasparovic H, Rybicki FJ, Millstine J, et al. Three-dimensional computed tomographic imaging in planning the surgical approach
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for redo cardiac surgery after coronary revascularization. Eur J Cardiothorac Surg 2005;28:244-9. Hendel RC, Patel MR, Kramer CM, et al. ACCF/ACR/SCCT/SCMR/ ASNC/NASCI/SCAI/SIR 2006 appropriateness criteria for cardiac computed tomography and cardiac magnetic resonance imaging: a report of the American College of Cardiology Foundation Quality Strategic Directions Committee Appropriateness Criteria Working Group, American College of Radiology, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, American Society of Nuclear Cardiology, North American Society for Cardiac Imaging, Society for Cardiovascular Angiography and Interventions, and Society of Interventional Radiology. J Am Coll Cardiol 2006;48:1475-97. Kamdar AR, Meadows TA, Roselli EE, et al. Multidetector computed tomographic angiography in planning of reoperative cardiothoracic surgery. Ann Thorac Surg 2008;85:1239-45. Gold JP. The Society of Thoracic Surgeons National Database. Available at: http://www.sts.org/sections/stsnationaldatabase/. Last accessed November 7, 2009. Thygesen K, Alpert JS, White HD, et al. Universal definition of myocardial infarction. Circulation 2007;116:2634-53. Roach GW, Kanchuger M, Mangano CM, et al. Adverse cerebral outcomes after coronary bypass surgery. Multicenter Study of Perioperative Ischemia Research Group and the Ischemia Research and Education Foundation Investigators. N Engl J Med 1996;335: 1857-63. Edwards FH, Clark RE, Schwartz M. Coronary artery bypass grafting: the Society of Thoracic Surgeons National Database experience. Ann Thorac Surg 1994;57:12-9. Mohammadi S, Dagenais F, Mathieu P, et al. Long-term impact of diabetes and its comorbidities in patients undergoing isolated primary coronary artery bypass graft surgery. Circulation 2007;116: I220-5. Leavitt BJ, Ross CS, Spence B, et al. Long-term survival of patients with chronic obstructive pulmonary disease undergoing coronary artery bypass surgery. Circulation 2006;114:I430-4. Aviram G, Sharony R, Kramer A, et al. Modification of surgical planning based on cardiac multidetector computed tomography in reoperative heart surgery. Ann Thorac Surg 2005;79:589-95.
Perioperative outcomes in reoperative cardiac surgery guided by cardiac multidetector computed tomographic angiography Gabriel Maluenda, MD, Matthew A. Goldstein, MD, Gilles Lemesle, MD, Gaby Weissman, MD, Guy Weigold, MD, Marc J. Landsman, BS, Peter C. Hill, MD, Francisco Pita, MD, Paul J. Corso, MD, Steven W. Boyce, MD, Augusto D. Pichard, MD, Ron Waksman, MD, and Allen J. Taylor, MD Washington, DC
Background Preoperative evaluation with contrast-enhanced multidetector computed tomographic angiography (MDCTA) is considered an “appropriate” indication based on expert consensus. We aimed to evaluate how the presurgical evaluation with MDCTA impacts the outcomes after reoperative cardiac surgery (RCS). Methods
We retrospectively studied 364 patients undergoing RCS between 2004 and 2008, including 137 referred for MDCTA. High-risk CT findings were defined as the presence of right ventricle or aorta b10 mm from the sternum or a bypass graft b10 mm from the sternum crossing the midline. The primary clinical end point was the composite of perioperative death, myocardial infarction (MI), stoke, and hemorrhage-related reoperation. Secondary end points included surgical procedural variables and the perioperative volume of bleeding and of red blood cell (RBC) transfusion.
Results Baseline clinical characteristics were similar between the 2 groups. Individuals referred for MDCTA showed a trend toward a lower incidence of the composite primary end point (17.5% vs 24.2%, P = .13), primarily related to a significantly lower incidence of perioperative MI (0% vs 5.7%, P = .002). Multidetector computed tomographic angiography was also associated with shorter perfusion (90 vs 110 minutes, P = .002), cross clamp time (63 vs 75 minutes, P = .003), and total time in intensive care unit (103 vs 148 hours, P = .04), and a lower volume of postoperative RBC transfusion (627 vs 824 mL, P = .09). These differences remained significant after adjustment for the Society of Thoracic Surgeons score and the performing surgeon. Conclusion
The use of MDCTA before RCS was associated with shorter perfusion and cross clamp time, shorter intensive care unit stays, and less frequent perioperative MI. (Am Heart J 2010;159:301-6.)
Reoperative cardiac surgery (RCS) carries a high mortality and morbidity1-5 due to increased technical difficulty as well as a higher prevalence and severity of coronary artery disease and comorbidities.2-7 The primary technical concern during surgical reentry is the presence of cardiovascular structures immediately beneath the sternum that pose a threat for injury. Of particular concern is the potential for injury of vital structures such as the right ventricle (RV), aorta, and coronary bypass grafts with catastrophic consequences.7,8 Thus, RCS represents a challenging situation for the cardiac surgical team where methods to reduce
From the Noninvasive Cardiovascular Imaging, Department of Medicine/Cardiology, Washington Hospital Center, and Cardiac Surgery Department, Washington Hospital Center, Washington, DC. Submitted August 27, 2009; accepted November 10, 2009. Reprint requests: Allen J. Taylor, MD, Department of Medicine, Section of Cardiology, 110 Irving St, NW, Room 1E12, Washington, DC 20010-2975. E-mail: [email protected] 0002-8703/$ - see front matter © 2010, Mosby, Inc. All rights reserved. doi:10.1016/j.ahj.2009.11.005
the occurrence of serious but preventable complications achieve paramount importance. One promising method to mitigate the risk of surgical reentry during RCS is through the use of contrastenhanced multidetector computed tomographic angiography (MDCTA). This technique comprehensively evaluates the structures of interest to the surgeon, including the chest wall, mediastinal structures, coronary bypass grafts, and their relationship to each other.9,10 The multisociety cardiac CT appropriateness criteria published in 2006 defined the use of MDCTA before repeat coronary surgery as an “appropriate” indication based upon expert consensus.11 However, there is little data to support this recommendation, with only a single center reporting on the frequency of high risk findings and possible changes to the surgical approach.12 Outcome data are needed to either support or refute the appropriateness criteria recommendation and inform clinical practice. The hypothesis of this retrospective study was that a MDCTA “roadmap” of substernal anatomy could guide the surgical approach and minimize the risk of injury upon surgical reentry. On the basis this potential benefit
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Figure 1
A, Axial view of MDCTA of the chest showing the absence of high-risk findings (LV, Left ventricle; RV, right ventricle; ST, sternum). B, Sagittal view of MDCTA of the thorax demonstrating the normal relationship between cardiac structures and the sternum (AA, Ascending aorta; PA, pulmonary artery; RA, right atrium; RV, right ventricle, ST, sternum).
of MDCTA to improve the safety of RCS, our center began performing MDCTA in 2004 for this indication. This study examines the relationship between presurgical evaluation with MDCTA and perioperative outcomes in patients undergoing RCS.
Methods and materials Study population We used the Society of Thoracic Surgeons (STS) database13 to identify patients who underwent RCS (n = 364) at the Washington Hospital Center (Washington, DC) between January 1, 2004, and December 31, 2008. Among these surgical patients, 137 were clinically referred for preoperative MDCTA, and 227 patients underwent RCS without MDCTA during the same period. All patients gave written consent for the proposed surgery, and this retrospective study was conducted under institutional review board approval.
Follow-up Baseline demographics, procedural data, and perioperative outcomes were recorded at the time of the procedure and entered in a computerized database by a dedicated datacoordinating center. All in-hospital adverse events were source documented and entered with standardized criteria in a computerized database by research nurses (exclusive of the nurses who performed the data collection). A separate team of research assistants collected follow-up clinical data by telephone questionnaire 30 days after discharge from the hospital, and events were similarly reconciled after reviewing the original source documents.
End points The primary end point prespecified by the study protocol was the composite rate of perioperative complications (myocardial infarction [MI], stroke, and hemorrhage-related reoperation) and operative death. The secondary end points included intraoperative hemodynamic outcomes (perfusion time and cross clamp time), total intensive care unit (ICU) time, the amount of perioperative bleeding and red blood cell (RBC) transfusions, and the rate of changes to the standard surgical approach, including the use of a nonmidline incision and a cannulation method excluding the aorta.
Multidetector computed tomographic angiography data acquisition and collection Cardiothoracic MDCTA was performed with 16-, 64-, or 256detector Brilliance scanners (Philips Medical Systems Inc, Cleveland, OH). Technical parameters were specific to the scanner generation used; however, all studies were performed with helical scanning with retrospective electrocardiographic gating and radiation dose modulation with ≤1-mm slice thickness and ≤90-mL isosmolar contrast. β-Blockers were used as needed to achieve a heart rate b65 beat/min. Acquisition was performed during a 10- to 20-second breathhold. Reconstructions included thin-slice (≤1 mm) reconstructions at middiastole and thick slice (2 mm) reconstructions at 10% intervals throughout the cardiac cycle for the cine-loop display. Scans were clinically interpreted by 1 of 4 experienced cardiac CT interpreters. High-risk findings on preoperative MDCTA were defined according to previously published criteria, with representative examples shown in Figures 1 to 3.12 These findings included (1) RV or aorta b1 cm below the sternal
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upper limit.14 Postoperative stroke was defined as any new major (type II) neurologic deficit presenting in-hospital and persisting for N72 hours.15 Hemorrhage-related reoperation was defined as urgent reexploration driven by bleeding or cardiac tamponade. Perfusion time was defined as the total of cardiopulmonary bypass and/or coronary perfusion assist minutes. Cross clamp time indicates the total number of minutes the aorta is completely cross clamped during bypass. Changes to the standard surgical approach were defined as the use of an incision avoiding the midline and/or a cannulation method for cardiopulmonary bypass excluding the aorta.
Statistical analysis
Axial view of MDCTA of the thorax showing a directly apposed free wall of the RV to the posterior aspect of the sternum, finding pointed by the arrow (LA, Left atrium; LV, left ventricle; RV, right ventricle; ST, sternum).
midline, (2) bypass grafts that crossed the midline within 1 cm posterior to the sternum, or (3) any cardiovascular structures adherent to the sternum as identified using cine-image display. Data were extracted from the electronic medical record based upon a standard scan interpretation methodology used at our institution.
Operative technique Standard anesthesia and surgical techniques, extracorporeal circulation, and myocardial protection methods were used for all patients. Patients underwent anticoagulation using 3 mg/kg of heparin sulfate to maintain an activated clotting time of ≥480 seconds. The institutional standardized protocol for blood product transfusion and for blood salvage was used. Aprotinin was not routinely administered. Desmopressin acetate was used in patients with renal insufficiency. Crystalloid solutions were used for volume replacement. All patients were rewarmed to 36°C before discontinuing the cardiopulmonary bypass. Normothermia was maintained during the intraoperative period after cardiopulmonary bypass. The clinical practice guidelines recommended blood transfusion at a hematocrit of b22% for patients b65 years old or b24% for patients ≥65 years old.
Definitions Operative mortality was defined as death occurring during the initial hospitalization or within 30 days after surgery. Perioperative MI was defined as new Q waves in 2 contiguous electrocardiogram leads or new left bundle branch block and elevation of the MB fraction of creatine kinase N5 times the
Continuous variables were expressed as mean ± SD. Categorical variables were expressed as absolute number and percentages. Baseline characteristics between the 2 groups—those with and without preoperative MDCTA—were compared by using the χ2 test or the Fisher test for categorical variables and the Student unpaired t test for continuous variables as appropriate. Multivariable logistic regression analysis controlling for differences in baseline covariates, weighted by the predicted risk of mortality and morbidity using the STS risk score16 and the primary surgeon were used to determine the independent relationship between MDCTA and perioperative outcomes after RCS. All statistical analysis was performed using SPSS version 16.0 (SPSS Inc, Chicago, IL). Statistical significance was assumed at P b .05. No extramural funding was used to support this work. The authors are solely responsible for the design and conduct of this study; all study analyses, and the drafting and editing of the article and its final contents.
Results The baseline clinical characteristics of the patients with and without MDCTA before RCS are shown in Table I. Both groups were similar in the clinical characteristics. As expected, there was a high prevalence of comorbidities, reflected by a high STS score for morbidity or mortality (27%). The MDCTA group had a higher prevalence of previous stroke (33.6% vs 20.7%) and higher prevalence of previous percutaneous coronary intervention (55.5% vs 41.0%). Most operations (53%) were isolated reoperative coronary artery bypass graft (CABG), 24% of the patients underwent valve surgery only, 20% had a combined CABG-valve procedure, and 3% of the cases had aortic aneurysm repair. Elective operations were performed in 51%, whereas 44% were urgent and 5% emergent, as defined by the STS. Perioperative complications including death (11%), MI (3.6%), stroke (4.1%), and hemorrhage-related reoperation (7.4%) are shown for the study groups in Table II. Patients referred for cardiac MDCTA showed a trend toward a lower incidence of the composite primary end point of death-MI-stroke-hemorrhage–related reoperation (17.5% vs 24.2%, P = .13), which was driven primary by a significantly lower incidence of perioperative MI in the MDCTA group (0% vs 5.7%, P = .002). All these
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Figure 3
A, Axial view of MDCTA of the thorax showing an adherent saphenous aortocoronary graft to the posterior aspect of the sternum at the midline, finding pointed by the arrow (AR, Aortic root; DA, descending aorta; LA, left atrium; LL, left lung; RV, right ventricle; RL, right lung; ST, sternum). B, Sagittal view of MDCTA of the chest demonstrating the same adherent saphenous aortocoronary graft to the posterior surface of the sternum at the midline level, remarked by the arrow.
Table I. Baseline clinical characteristics
Age, y ± SD Male, n (%) Diabetes, n (%) Hypertension, n (%) Previous smoking, n (%) Hypercholesterolemia, n (%) BMI, kg/m2 ± SD Family history of CAD, n (%) History of MI, n (%) History of PCI, n (%) History of CHF, n (%) History of stroke, n (%) History of PVD, n (%) History of CLD, n (%) Serum creatinine level, mg/dL Left ventricular EF, % ± SD STS risk score of death and morbidity, ± SD
Table II. Postoperative outcomes regarding the use of preoperative MDCTA
MDCTA (n = 137)
No MDCTA (n = 227)
P
68.3 ± 9.2 101 (73.5) 48 (35.0) 119 (86.9) 81 (59.1) 125 (91.2) 28.6 ± 4.9 77 (57.0) 62 (45.6) 76 (55.5) 44 (32.1) 46 (33.6) 29 (21.3) 33 (24.1) 1.38 ± 1.32 45.4 ± 10.5 0.258 ± 0.161
68.1 ± 9.6 176 (77.5) 102 (44.9) 196 (86.3) 136 (60.4) 202 (89.0) 28.3 ± 5.2 129 (59.7) 118 (54.6) 93 (41.0) 76 (33.6) 47 (20.7) 54 (24.0) 42 (18.6) 1.58 ± 1.72 43.1 ± 11.7 0.273 ± 0.188
.78 .41 .063 .89 .80 .49 .62 .62 .098 .007 .77 .006 .56 .21 .24 .053 .49
BMI, Body mass index; CAD, coronary artery disease; MI, myocardial infarction; PCI, percutaneous coronary intervention; CHF, congestive heart failure; PVD, peripheral vascular disease; CLD, chronic lung disease; EF, ejection fraction; SD, standard deviation.
differences remained statistically significant after adjustment for the STS score and the performing surgeon (OR 0.50, 95% CI 0.25-1.0, P = .05). Preoperative MDCTA was associated with shorter perfusion (90 vs 110 minutes, P = .002) and cross clamp time (63 vs 75 minutes, P = .003), reduced total time in the ICU (103 vs 148 hours, P = .042), and a trend toward lower volume of postoperative of RBC transfusions (627 vs 824 mL, P = .09).
Death, n (%) Myocardial infarction, n (%) Stroke, n (%) Urgent reoperation, n (%) Composite primary end point, n (%) Perfusion time, min ± SD Cross clamp time, min ± SD Total time in ICU, h ± SD Intraoperative estimated blood loss, mL ± SD Intraoperative RBC transfusion, mL ± SD Postoperative RBC transfusion, mL ± SD Intraoperative and postoperative RBC transfusion, mL ± SD No middle incision, n (%) Cannulation excluding aorta, n (%)
MDCTA (n = 137)
No MDCTA (n = 227)
P
15 (10.9) 0 5 (3.6) 13 (9.5) 24 (17.5)
25 (11.0) 13 (5.7) 10 (4.4) 14 (6.2) 55 (24.2)
.99 .002 .79 .24 .13
110.1 ± 63.8 74.8 ± 38.0 148.0 ± 225.6 643.4 ± 375.9
.002 .003 .042 .61
90.1 62.6 103.0 624.1
± 34.2 ± 23.7 ± 162.0 ± 313.4
611.3 ± 545.6 627.0 ± 823.7
585.9 ± 596.6 .66
1233.7 ± 1083.9
824.1 ± 1175.8 1406.4 ± 1473.5
3 (2.2) 5 (3.6)
9 (4.0) 10 (4.4)
.09 .24
.55 .79
ICU, Intensive care unit; RBC, red blood cell; SD, standard deviation.
Among the subgroup that underwent MDCTA, the presence of a high-risk RV finding was associated with a significantly higher volume of intraoperative estimated blood loss (P = .04), intraoperative RBC transfusions (P = .03), and the total amount of RBCs transfused during and after the surgery (P = .01) (Table III). The presence of
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Table III. Postoperative outcomes regarding the presence of high-risk findings RV at high risk
Perfusion time, min ± SD Cross clamp time, min ± SD Total time in ICU, h ± SD Intraoperative estimated blood loss, mL ± SD Intraoperative RBC transfusion, mL ± SD Intraoperative and postoperative RBC transfusion, mL ± SD No middle incision, n (%) Cannulation excluding aorta, n (%)
Graft at high risk
High risk (n = 104)
No high risk (n = 33)
P
High risk (n = 21)
No high risk (n = 116)
P
88.7 ± 31.5 61.8 ± 22.6 115.5 ± 160.7 654 ± 332 668 ± 555 1365.6 ± 1141.1 3 (1.9) 5 (4.8)
95.5 ± 44.3 66.1 ± 28.3 63.4 ± 162.0 529 ± 431 432 ± 477 818.2 ± 753.3 1 (3.0) 0
0.41 0.45 0.11 0.045 0.03 0.011 0.7 0.19
98.9 ± 39.0 65.4 ± 19.5 101.5 ± 89.3 678 ± 251 678 ± 475 1357 ± 673 1 (4.8) 4 (19)
88.3 ± 33.1 62.1 ± 24.5 103.2 ± 172.2 614 ± 323 599 ± 558 1211 ± 1143 2 (1.7) 1 (0.9)
.31 .26 .37 .82 .63 .09 .38 b.001
ICU, Intensive care unit; RBC, red blood cell; SD, standard deviation.
other high-risk findings, in particular bypass grafts crossing the midline near the sternum, were not associated with the occurrence of any adverse outcomes. However, changes to the standard surgical approach, in particular the adoption of an alternative cannulation method excluding the aorta, were associated with the presence of high-risk graft findings (P b .001) but not to other high-risk findings.
Discussion This study shows that the use of MDCTA before RCS was associated with less frequent perioperative MI, shorter operative hemodynamic times, shorter ICU stays, and trends toward lower volume of RBC transfusions after the surgery. Among potentially high-risk MDCTA findings, and in particular high-risk RV findings, we noted a higher risk of bleeding and RBC transfusion during and after the surgery. The higher risk of perioperative complications during RCS2-4 is multifactorial. Patient-related factors include a greater extent of the coronary artery disease and comorbidities.2,5,17,18 Technical factors include substernal structures at risk for injury during surgical reentry, more complex dissection with risk to coronary bypass grafts, and increased perioperative blood loss. Accordingly, our results are consistent with the concept that guidance of surgical reentry and dissection through preoperative MDCTA leads to improved outcomes including faster operative times, less risk for perioperative MI, lower rates of bleeding, and shorter ICU stays after the procedure. Our study identifies high-risk RV findings as a marker of potential bleeding complications. The lower incidence of perioperative MI among patients receiving MDCTA is notable and may have arisen through less manipulation of in situ bypass grafts. However, we urge caution in interpretation of this finding within a single component of the composite primary end point. The use of preoperative MDCTA has been previously reported. Two small reports described the potential benefit of the 16-slice MDCTA for modification of the
surgical plan.10,19 In addition, Kamdar et al12 published a series of 167 patients with prior CABG who underwent RCS with preoperative MDCTA evaluation. They showed that routine use of MDCTA before RCS detects high-risk findings that were strongly associated with the adoption of preventive surgical strategies. However, they did not report any relationship to perioperative outcomes. Indeed, we also found an association between the presences of high-risk graft findings and the adoption of an alternative cannulation method but importantly extend these results to include perioperative outcomes. The 2006 multisociety appropriateness criteria for cardiac CT identified the use of CT before RCS as an “appropriate” indication.11 Guided by expert opinion, subsequent evidence, including the present study, appears to support this recommendation. However, in the absence of a randomized controlled trial, definitive conclusions regarding the impact of preoperative MDCTA must be made with caution. Additional prospective data from surgical registries should be collected to confirm our results. Findings from this study could be used to inform the design and sample size for clinical trial planning. There are limitations to our study. This is a retrospective analysis centered on a prespecified end point using concurrent surgical populations. Although the study groups were well matched, the potential for confounding by unmeasured variables must be considered. We attempted to broadly adjust for potential differences among patients with and without preoperative MDCTA by adjusting for surgical risk using the well-validated STS risk score. The observed association of MDCTA with improved perioperative outcomes cannot be causally attributed to MDCTA alone. This analysis was underpowered to establish direct relationship between the presence of high-risk MDCTA findings and the frequency of changes to the standard surgical approach. However, during the study period, no patients were refused RCS based upon MDCTA findings. Moreover, the findings are consistent with the concept that MDCTA guidance aided the technical performance of the operation.
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In conclusion, the use of MDCTA before RCS was associated with improved perioperative outcomes including shorter operative times and ICU stays and less frequent perioperative MI. Among MDCTA findings, the presences of high-risk RV findings are associated with a higher amount of bleeding during and after the surgery.
11.
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