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Off-Pump Strategy in High-Risk Coronary Artery Bypass Reoperations
ORIGINAL ARTICLE
OFF-PUMP CORONARY ARTERY BYPASS GRAFTING FOR HIGH-RISK REOPERATION
Off-Pump Strategy in High-Risk Coronary Artery Bypass Reoperations DUMBOR L. NGAAGE, MBBS, MS; KENTON J. ZEHR, MD; RICHARD C. DALY, MD; THORALF M. SUNDT III, MD; CHARLES J. MULLANY, MBMS; JOSEPH A. DEARANI, MD; THOMAS A. ORSZULAK, MD; AND HARTZELL V. SCHAFF, MD OBJECTIVE: To determine the role of off-pump coronary artery bypass grafting in the treatment of patients with severe recurrent angina after coronary artery bypass grafting who are not suitable for percutaneous coronary intervention and are considered too high risk for conventional on-pump revascularization. PATIENTS AND METHODS: All patients who needed single- or double-vessel revascularization at reoperation with a predicted operative mortality of 10% or higher between March 4, 1994, and December 31, 2002, were studied. Risk stratification was performed using both the Parsonnet risk scoring system and the European System for Cardiac Operative Risk Evaluation. Active followup by questionnaire investigated major adverse cardiac events. RESULTS: This study consisted of 84 patients with a median age of 69 years (interquartile range, 62-75 years); 14 (17%) were female. All patients had class III/IV symptoms. Previous operations included multiple coronary artery bypass grafts (15 patients [18%]) and heart transplantation (1 patient [1%]). Internal thoracic artery graft from a previous operation was patent in 43 patients (51%). Perioperative hemodynamic support with inotropes (35%) and intra-aortic balloon pump (14%) or ventricular assist device (2%) was common. The surgical approach varied for each patient. One operative death (1%) occurred. Estimated survival at 5 and 7 years was 77% and 67%, respectively. Late major adverse cardiac events observed during follow-up were cardiac death (n=66), nonoperative reintervention (n=8), and nonfatal myocardial infarction (n=5). CONCLUSION: Off-pump coronary artery bypass grafting can mitigate reoperative risk in patients with an estimated risk of 10% or higher who are undergoing single- or double-vessel revascularization with satisfactory long-term outcome.
Mayo Clin Proc. 2007;82(5):567-571 CABG = coronary artery bypass grafting; CI = confidence interval; EuroSCORE = European System for Cardiac Operative Risk Evaluation; MIDCAB = minimally invasive coronary artery bypass grafting; OPCAB = off-pump coronary artery bypass grafting; RR = risk ratio
O
ff-pump coronary artery bypass grafting (OPCAB) has evolved into a strategy that is complementary to on-pump coronary artery bypass grafting (CABG). However, patient selection for this procedure continues to generate interest. In the current era of coronary surgery, patients
From the Division of Cardiovascular Surgery, College of Medicine, Mayo Clinic, Rochester, Minn. Dr Zehr is now with the University of Pittsburgh Medical Center, Pittsburgh, Pa. Individual reprints of this article are not available. Address correspondence to Dumbor L. Ngaage, MBBS, at his current address: Department of Cardiothoracic Surgery, Castle Hill Hospital, Cottingham, East Yorkshire HU15 6JQ, United Kingdom (e-mail: [email protected]). © 2007 Mayo Foundation for Medical Education and Research
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frequently present for a reoperation in which revascularization using cardiopulmonary bypass is high risk. Although repeated coronary surgery by itself may no longer be considered high risk, sometimes patient characteristics and comorbidities escalate the risk of on-pump CABG reoperation.1-3 This subgroup of patients often presents a management dilemma. Alternative strategies of surgical revascularization, including OPCAB, have been explored in various subsets of these patients.4-10 Avoiding cardiopulmonary bypass has potential benefits,11,12 but concerns have been raised about the integrity of the coronary anastomosis on a beating heart and incomplete revascularization.13 Nonetheless, various studies have shown that OPCAB may have an added advantage in select groups of patients, including those who need reoperations,14-18 thereby emphasizing the importance of patient selection. However, data on late adverse outcomes, such as recurrent symptoms and cardiac events, are lacking. Although many studies have reported early results in different subsets of patients with specific comorbidities, few have investigated late results in high-risk patients defined by calculated surgical risks. The purpose of this study is to determine the role of OPCAB in the treatment of patients with severe, recurrent angina after CABG who are not suitable for percutaneous coronary intervention and are considered too high risk for conventional on-pump revascularization. Both the Parsonnet risk scoring system and the European System for Cardiac Operative Risk Evaluation (EuroSCORE) were used to identify patients with high predicted operative mortality.19-21 Operative outcome and late adverse events were evaluated to determine whether OPCAB is a viable alternative with durable results in this subset of patients. PATIENTS AND METHODS We used our institution’s cardiovascular surgery database to identify all patients who underwent repeated surgical myocardial revascularization with the off-pump technique because they were considered at high operative risk for repeated conventional on-pump CABG at our institution from March 4, 1994, through December 31, 2002. The Mayo Clinic Institutional Review Board approved this study in September 2003, and consent was obtained from
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OFF-PUMP CORONARY ARTERY BYPASS GRAFTING FOR HIGH-RISK REOPERATION
all the patients. The operative risk of the patients was calculated using the Parsonnet multivariate logistic regression model and the additive EuroSCORE. All patients had an operative risk of 10 or greater by both risk-scoring systems. Twelve patients (14%) were denied repeated CABG at different facilities because of excessive surgical risk. Most of the patients had patent grafts from previous surgery and needed 1 or 2 grafts. The demographic characteristics, clinical symptoms, comorbidities, and perioperative details of the patients were collated by medical record review. SURGICAL TECHNIQUE The surgical access considered optimal for repeated revascularization was chosen for each patient on the basis of clinical profile and coronary angiographic findings. Therefore, operative approaches included limited thoracotomy incisions (minimally invasive coronary artery bypass grafting [MIDCAB]), full thoracotomy, and median sternotomy. Vessel stabilization was achieved by gentle snaring of target vessels with Silastic loops in the early period and later with local compression or suction devices. Visualization was facilitated by the use of carbon dioxide and isotonic sodium chloride solution blower systems. Distal and proximal anastomoses were handsewn in the usual fashion. FOLLOW-UP The Social Security Death Index was queried, and death certificates were obtained for all nonsurvivors. A follow-up survey questionnaire was sent to all survivors in March 2005 to investigate current symptoms, repeated cardiac interventions, repeated coronary angiograms, and cardiacrelated hospital readmissions. This was followed by telephone calls for a few nonresponders. Also, for patients who visited a Mayo Clinic facility for continued care, other follow-up information, such as postoperative angiography, stress echocardiography, and radionuclide viability studies, was retrieved from the Mayo Integrated Clinical System. STATISTICAL ANALYSES The primary end points were early or late death and repeated cardiac intervention. Categorical variables are expressed as percentages and continuous variables as the median and interquartile range, unless otherwise stated. Univariate analysis was performed using the χ2 test for categorical data, Wilcoxon rank sum test for continuous data, and Kaplan-Meier method for long-term outcomes. The proportional hazards model was used to identify variables associated with poor long-term survival. Models were constructed using categorical variables (sex, diabetes, renal failure, prior CABG, valve operation, myocardial infarction, history of heart failure, stroke, angina class, 568
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New York Heart Association class, preexisting atrial fibrillation, surgical priority, and chronic obstructive pulmonary disease) and continuous variables (age, body mass index, number of prior cardiac operations, left ventricular ejection fraction, Parsonnet score, and EuroSCORE). Statistical significance was defined as P<.05 with a 2-tailed test. Statistical analysis was performed using JMP Statistical Discovery Software (SAS Institute Inc, Cary, NC). RESULTS BASELINE AND OPERATIVE DETAILS Eighty-four patients with a median age of 69 years (range, 49-86 years) were included in the study; 14 (17%) were females. At the time of reoperation, all patients had severe recurrent angina (class III and IV). One patient (1%) had undergone heart transplantation previously, and 15 (18%) had more than 1 previous CABG operation. Preoperative coronary angiography revealed that the left internal thoracic artery was used as a bypass conduit in 60 patients (71%) but was patent in 43 (51%). All previous CABG operations were performed using cardiopulmonary bypass, and the median interval between the last CABG procedure and the reoperative OPCAB was 10 years (range, 0-35 years). The calculated median operative risk was 12 (range, 10-15) based on the EuroSCORE and 14 (range, 11-19) based on the Parsonnet multivariate logistic regression model. Thirty patients (36%) had a left ventricular ejection fraction of 40% or less. Table 1 outlines the baseline characteristics of the study population. MIDCAB incisions were used in 10 patients (12%), left thoracotomy in 26 (31%), and median sternotomy in 48 (57%). In most patients, arterial conduits were used, and the descending thoracic aorta was often the site for proximal anastomoses. Perioperative hemodynamic support was necessary with inotropes in 29 patients (35%), intra-aortic balloon pump in 12 (14%), and ventricular assist device in 2 (2%). One in-hospital death (1%) occurred. The operative details and outcome are outlined in Table 2. LATE OUTCOME Table 3 details the late clinical outcomes. The average duration of postoperative follow-up, defined as the mean interval between hospital discharge and the survey questionnaire, was 3.6 years (maximum, 9 years). During this period, 17 late postoperative deaths occurred, mainly from cardiac causes (12 patients). The Kaplan-Meier estimates for overall late mortality at 1, 3, and 5 years were 6% (95% confidence interval [CI], 3%-17%), 11% (95% CI, 5%22%), and 23% (95% CI, 10%-37%), respectively; Figure 1 shows the survival rates. Univariate determinants of poor long-term survival were body mass index (risk ratio [RR],
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OFF-PUMP CORONARY ARTERY BYPASS GRAFTING FOR HIGH-RISK REOPERATION
TABLE 1. Clinical Profile of 84 Patients Undergoing Repeated Off-Pump CABG*
TABLE 2. Perioperative Details of 84 Patients Undergoing Reoperations*
Characteristic
Value
Characteristic
Mean age (y) (IQR) Female Median body mass index (IQR) Presenting symptoms Angina class III IV Cardiogenic shock Cardiac morbidity Atrial fibrillation Myocardial infarction Median ejection fraction (%) (IQR) (n=80) Prior cardiac operation 1 previous CABG 2 previous CABGs Valve repair or replacements Heart transplantation LITA graft Not used Patent Stenosed Median interval from last operation (y) (IQR) Comorbidities Diabetes mellitus Renal failure Stroke Chronic obstructive pulmonary disease Peripheral vascular disease Median risk stratification values (IQR) Additive EuroSCORE Parsonnet multivariate logistic regression
69 (62-75) 14 (17) 28 (25-32)
Incision Median sternotomy Left thoracotomy Minimally invasive Vessel stabilization Snare Suction Compression No. of distal anastomosis 1 2 Site of distal anastomosis Left anterior descending artery territory† Circumflex territory† Right coronary artery territory Site of proximal anastomosis None Ascending aorta Descending aorta Nongraft arteries In situ grafts Arterial conduits Internal thoracic artery Left Right Bilateral Radial artery Surgical priority Elective Urgent Emergent Conversion to on-pump technique Perioperative cardiovascular support Inotropes Intra-aortic balloon pump Ventricular assist device Renal function impairment Stroke Operative mortality Median hospital length of stay (d) (IQR)
52 (62) 32 (38) 3 (4) 28 (33) 37 (44) 47 (35-60) 69 (82) 15 (18) 8 (10) 1 (1) 24 (29) 43 (51) 17 (20) 10 (6-15) 29 (35) 16 (19) 8 (10) 17 (20) 34 (40) 12 (10-15) 14 (11-19)
*Data are number (percentage) of patients unless otherwise indicated. CABG = coronary artery bypass grafting; EuroSCORE = European System for Cardiac Operative Risk Evaluation; IQR = interquartile range; LITA = left internal thoracic artery.
1.8; 95% CI, 1.7-2.0; P=.02), diabetes mellitus (RR, 1.5; 95% CI, 1.3-1.8; P=.003), chronic obstructive pulmonary disease (RR, 3.2; 95% CI, 1.1-10.5; P=.04), urgent or emergent surgery (RR, 4.1; 95% CI, 1.3-13.0; P=.05), EuroSCORE (RR, 1.3; 95% CI, 1.1-1.5; P=.002), and Parsonnet score (RR, 1.05; 95% CI, 1.01-1.08; P=.01). Nonfatal myocardial infarction was uncommon and occurred in 5 patients. Significant improvement in symptoms as measured by change in angina class (P<.001) and New York Heart Association functional class (P<.001) was experienced by patients at late follow-up as shown in Table 4. None of the patients had angina class IV symptoms, and only 10% had class III symptoms. Tests of graft patency were performed in 46 (70%) of the 66 surviving patients primarily to investigate symptoms. The indications for reinvestigations were (1) severe recurrent angina, (2) worsening dyspnea, (3) myocardial infarction, and (4) evaluation for noncardiac operation. Coronary angiography was performed in 25 patients, radioactive scanning in 17, and stress echocardiography in 4. Of Mayo Clin Proc.
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Value 48 (57) 26 (31) 10 (12) 9 (11) 24 (29) 51 (61) 67 (80) 17 (20) 48 (57) 35 (42) 14 (17) 25 (30) 18 (21) 29 (35) 3 (4) 9 (11) 37 (44) 21 (57) 12 (32) 4 (11) 20 (24) 53 (63) 29 (35) 2 (2) 1 (1) 29 (35) 12 (14) 2 (2) 9 (11) 3 (4) 1 (1) 6.5 (5-9)
*Data are number (percentage) of patients unless otherwise indicated. IQR = interquartile range. †Three patients had grafts to the left anterior descending and diagonal arteries (both left anterior descending territory), and 4 patients had grafts to 2 arteries in the circumflex territory.
the 25 patients with severe recurrent symptoms, postoperative coronary angiography revealed patent grafts in 19. DISCUSSION We found that OPCAB is a viable alternative strategy for repeated myocardial revascularization in patients not suitable for percutaneous intervention and at excessive operative risk for on-pump CABG. With selective use of this technique, and when appropriate in combination with MIDCAB incisions, we found a 90% reduction in the operative mortality predicted using conventional risk-scoring systems in this high-risk group of patients. Dewey et al15
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TABLE 3. Late Clinical Outcomes After Repeated Off-Pump Coronary Artery Bypass Grafting* Outcome
Value
Death Cardiac events observed Nonfatal myocardial infarction Death Overall late mortality (Kaplan-Meier estimates) (%) (95% CI) 1y 2y 3y Postoperative investigations (n=66) Coronary angiography Radioactive isotope scanning Stress echocardiography Status of graft(s) (n=25) Patent Occluded Angina class (n=53) I II III IV Medications (n=36) β-Blockers ACE inhibitors Aspirin Statin Warfarin Diuretic
17
100
Patients alive (%)
80
5 12 6 (3-17) 11 (5-22) 23 (10-37)
60
40
25 (38) 17 (26) 4 (6)
1-y survival: 94% 5-y survival: 77%
20
19 (76) 6 (24) 2
32 (60) 12 (23) 9 (17) 0 (0) 30 (83) 23 (64) 34 (94) 33 (92) 11 (31) 23 (64)
*Data are number (percentage) of patients unless otherwise indicated. ACE = angiotensin-converting enzyme; CI = confidence interval.
reported a similar finding using the Society of Thoracic Surgeons algorithm for predicted mortality. They reported a reduction in observed mortality in a subset of 153 patients who underwent repeated OPCAB compared with 279 who underwent on-pump CABG. The benefit of this strategy for high-risk reoperations is multifactorial. These patients often have some patent grafts and require target vessel revascularization; thus, incomplete revascularization is not a concern. Consequently, extensive dissection and mobilization for cannulation with the risk of iatrogenic injury are unnecessary. In addition, the deleterious effects of cardiopulmonary bypass are avoided, as are the problems of myocardial protection that can be challenging in these patients. Moreover, the selective use of limited incisions combines the advantages of MIDCAB with avoiding the cardiopulmonary bypass. Finally, the risk stratification systems designed for on-pump CABG may overestimate the risk of OPCAB.
4
6
Time after surgery (y) No. at risk 83
53
26
13
FIGURE 1. Kaplan-Meier survival curve of high-risk patients after offpump coronary artery bypass reoperation.
Major adverse cardiac events such as cardiac death, nonfatal myocardial infarction, and repeated cardiac intervention were not common in the long term. At 3, 5, and 7 years, respectively, the freedom from cardiac death was 98%, 83%, and 70%, and the overall survival times were 89% (95% CI, 77%-95%), 77% (95% CI, 63%-91%), and 67% (95% CI, 46%-81%). Even though these patients had significant comorbidities, the most common cause of late death was cardiac related. However, patient comorbidities such as diabetes and chronic obstructive pulmonary disease added an incremental effect on the risk of late mortality. Surgical risk stratification using the Parsonnet system and EuroSCORE captures patient characteristics and comorbidity and explains the association of a high-risk score with poor longterm survival. Graft patency after OPCAB has been questioned in the past, but Puskas et al22 showed that early patency rates were comparable to those after on-pump CABG for primary procedures. In patients undergoing repeated CABG, we know of no study that reports graft patency. In our select group of high-risk patients, we found a late patency rate of
TABLE 4. Pairwise Comparison of Preoperative and Postoperative Variables* Variables Mean angina class (n=53) Mean NYHA class (n=48) Mean EF (%) (n=43)
Preoperative
Postoperative
Difference (95% CI)
P value
3.2 3.4 46.6
1.4 1.7 45.4
1.8 (1.5 to 2.2) 1.7 (1.3 to 2.2) –1.2 (–5.6 to 3.2)
<.001 <.001 .60
*CI = confidence interval; EF = ejection fraction; NYHA = New York Heart Association.
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OFF-PUMP CORONARY ARTERY BYPASS GRAFTING FOR HIGH-RISK REOPERATION
76% in a subgroup reinvestigated for recurrent symptoms. Therefore, it is self-evident that this patency rate is an underestimation. The selection of patients with a greater propensity to graft occlusion for repeated angiography underpins the low late graft patency rate observed in this cohort of patients. Also, early postoperative angiography, which was performed to diagnose 5 of 6 occluded grafts, can be misleading, especially for arterial grafts. We previously reported the drawbacks of this procedure23 in a study that showed that 86% of grafts that were angiographically occluded in the early postoperative period were probe patent at immediate reoperation. Spasm of both the native coronary artery and arterial graft can be difficult to distinguish from true occlusion at angiography; thus, early postoperative angiography is an unreliable method to detect graft occlusion. The role of OPCAB in the management of coronary artery disease continues to be investigated. These data support the selective use of this technique in patients at high risk of reoperation and in combination with MIDCAB incisions when appropriate. This study examines the early and long-term clinical results in a group of patients with high predicted operative risk determined by objective and internationally accepted risk stratification systems used routinely in cardiac surgery. Other studies have defined high risk solely on the basis of specific comorbid disease conditions16,18,24 or complications of coronary artery disease25,26 or reoperation,7,27 but this study addresses a clinical dilemma increasingly encountered in practice: the patient with severe recurrent angina after CABG with patent graft(s) who requires 1 or 2 bypass grafts. Like all retrospective studies, our study has the inherent drawbacks of patient selection bias, recall bias, and incomplete data on some patients, but the active follow-up with a survey questionnaire provides supplementary data to offset some of these limitations. Because the study population was a highly select group, it was not possible to identify a similar group of patients who underwent on-pump CABG for comparison. However, the risk-scoring systems used in the study are reliable in predicting the operative result of conventional on-pump CABG. CONCLUSION Patients at excessive risk of reoperative CABG pose a management challenge. We found that OPCAB may be a suitable alternative in patients with an estimated risk of reoperation of 10% and higher who require 1 or 2 grafts. Its selective use can mitigate operative mortality with satisfactory late outcomes. We found a significant reduction in reoperative mortality with a low rate of major adverse cardiac events and acceptable long-term survival with the offpump technique combined with a tailored surgical access. Mayo Clin Proc.
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REFERENCES 1. Christenson JT, Schmuziger M, Simonet F. Reoperative coronary artery bypass procedures: risk factors for early mortality and late survival. Eur J Cardiothorac Surg. 1997;11:129-1833. 2. Di Mauro M, Iaco AL, Contini M, et al. Reoperative coronary artery bypass grafting: analysis of early and late outcomes. Ann Thorac Surg. 2005;79:81-87. 3. Sabik JF III, Blackstone EH, Houghtaling PL, Walts PA, Lytle BW. Is reoperation still a risk factor in coronary artery bypass surgery? Ann Thorac Surg. 2005;80:1719-1727. 4. Azoury FM, Gillinov AM, Lytle BW, Smedira NG, Sabik JF. Off-pump reoperative coronary artery bypass grafting by thoracotomy: patient selection and operative technique. Ann Thorac Surg. 2001;71:1959-1963. 5. Detter C, Reichenspurner H, Boehm DH, et al. Minimally invasive direct coronary artery bypass grafting (MIDCAB) and off-pump coronary artery bypass grafting (OPCAB): two techniques for beating heart surgery. Heart Surg Forum. 2002;5:157-162. 6. Kuniyoshi Y, Yamashiro S, Miyagi K, Uezu T, Arakaki K, Koja K. Offpump redo coronary artery bypass grafting via left thoracotomy. Ann Thorac Cardiovasc Surg. 2003;9:378-383. 7. Mack MJ. Off-pump surgery and alternatives to standard operation in redo coronary surgery. J Card Surg. 2004;19:313-319. 8. Miyaji K, Wolf RK, Flege JB Jr. Minimally invasive direct coronary artery bypass for redo patients. Ann Thorac Surg. 1999;67:1677-1681. 9. Stamou SC, Pfister AJ, Dullum MK, et al. Late outcome of reoperative coronary revascularization on the beating heart. Heart Surg Forum. 2001;4:69-73. 10. Vassiliades TA Jr, Nielsen JL. Alternative approaches in off-pump redo coronary artery bypass grafting. Heart Surg Forum. 2000;3:203-206. 11. Parolari A, Alamanni F, Cannata A, et al. Off-pump versus on-pump coronary artery bypass: meta-analysis of currently available randomized trials. Ann Thorac Surg. 2003;76:37-40. 12. Stallwood MI, Grayson AD, Mills K, Scawn ND. Acute renal failure in coronary artery bypass surgery: independent effect of cardiopulmonary bypass. Ann Thorac Surg. 2004;77:968-972. 13. Ngaage DL. Off-pump coronary artery bypass grafting: the myth, the logic and the science. Eur J Cardiothorac Surg. 2003;24:557-570. 14. Al-Ruzzeh S, Nakamura K, Athanasiou T, et al. Does off-pump coronary artery bypass (OPCAB) surgery improve the outcome in high-risk patients? a comparative study of 1398 high-risk patients. Eur J Cardiothorac Surg. 2003;23:50-55. 15. Dewey TM, Magee MJ, Acuff T, et al. Beating heart surgery reduces mortality in the reoperative bypass patient. Heart Surg Forum. 2002;5(suppl 4):S301-S316. 16. Nishimura J, Akagi H, Sawa Y, et al. Advantages of off-pump coronary artery bypass grafting in long-term hemodialysis patients: multicenter analysis. Heart Surg Forum. 2004;7:E370-E373. 17. Stamou SC, Jablonski KA, Hill PC, Bafi AS, Boyce SW, Corso PJ. Coronary revascularization without cardiopulmonary bypass versus the conventional approach in high-risk patients. Ann Thorac Surg. 2005;79:552-557. 18. Tabata M, Takanashi S, Fukui T, et al. Off-pump coronary artery bypass grafting in patients with renal dysfunction. Ann Thorac Surg. 2004;78:2044-2049. 19. Berman M, Stamler A, Sahar G, et al. Validation of the 2000 BernsteinParsonnet score versus the EuroSCORE as a prognostic tool in cardiac surgery. Ann Thorac Surg. 2006;81:537-540. 20. Nashef SA, Roques F, Hammill BG, et al, EuroSCORE Project Group. Validation of European System for Cardiac Operative Risk Evaluation (EuroSCORE) in North American cardiac surgery. Eur J Cardiothorac Surg. 2002;22:101-105. 21. Nashef SA, Roques F, Michel P, Gauducheau E, Lemeshow S, Salamon R. European system for cardiac operative risk evaluation (EuroSCORE). Eur J Cardiothorac Surg. 1999;16:9-13. 22. Puskas JD, Thourani VH, Marshall JJ, et al. Clinical outcomes, angiographic patency, and resource utilization in 200 consecutive off-pump coronary bypass patients. Ann Thorac Surg. 2001;71:1477-1483. 23. Zehr KJ, Handa N, Bonilla LF, Abel MD, Holmes DR Jr. Pitfalls and results of immediate angiography after off-pump coronary artery bypass grafting. Heart Surg Forum. 2000;3:293-299. 24. Osaka S, Ohsawa H, Nabuchi A. Redo off-pump coronary artery bypass grafting for high risk hemodialysis patients. J Card Surg. 2002;17:383-386. 25. Jasinski MJ, Wos S, Olszowka P, et al. Primary OPCAB as a strategy for acute coronary syndrome and acute myocardial infarction. Heart Surg Forum. 2003;6:331-335. 26. Vlassov GP, Deyneka CS, Travine NO, Timerbaev VH, Ermolov AS. Acute myocardial infarction: OPCAB is an alternative approach for treatment. Heart Surg Forum. 2001;4:147-150. 27. Moore GJ, Pfister A, Trachiotis GD. Outcomes for off-pump coronary artery bypass grafting in high-risk groups: a historical perspective. Heart Surg Forum. 2005;8:E19-E22.
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Off-Pump Strategy in High-Risk Coronary Artery Bypass Reoperations DUMBOR L. NGAAGE, MBBS, MS; KENTON J. ZEHR, MD; RICHARD C. DALY, MD; THORALF M. SUNDT III, MD; CHARLES J. MULLANY, MBMS; JOSEPH A. DEARANI, MD; THOMAS A. ORSZULAK, MD; AND HARTZELL V. SCHAFF, MD OBJECTIVE: To determine the role of off-pump coronary artery bypass grafting in the treatment of patients with severe recurrent angina after coronary artery bypass grafting who are not suitable for percutaneous coronary intervention and are considered too high risk for conventional on-pump revascularization. PATIENTS AND METHODS: All patients who needed single- or double-vessel revascularization at reoperation with a predicted operative mortality of 10% or higher between March 4, 1994, and December 31, 2002, were studied. Risk stratification was performed using both the Parsonnet risk scoring system and the European System for Cardiac Operative Risk Evaluation. Active followup by questionnaire investigated major adverse cardiac events. RESULTS: This study consisted of 84 patients with a median age of 69 years (interquartile range, 62-75 years); 14 (17%) were female. All patients had class III/IV symptoms. Previous operations included multiple coronary artery bypass grafts (15 patients [18%]) and heart transplantation (1 patient [1%]). Internal thoracic artery graft from a previous operation was patent in 43 patients (51%). Perioperative hemodynamic support with inotropes (35%) and intra-aortic balloon pump (14%) or ventricular assist device (2%) was common. The surgical approach varied for each patient. One operative death (1%) occurred. Estimated survival at 5 and 7 years was 77% and 67%, respectively. Late major adverse cardiac events observed during follow-up were cardiac death (n=66), nonoperative reintervention (n=8), and nonfatal myocardial infarction (n=5). CONCLUSION: Off-pump coronary artery bypass grafting can mitigate reoperative risk in patients with an estimated risk of 10% or higher who are undergoing single- or double-vessel revascularization with satisfactory long-term outcome.
Mayo Clin Proc. 2007;82(5):567-571 CABG = coronary artery bypass grafting; CI = confidence interval; EuroSCORE = European System for Cardiac Operative Risk Evaluation; MIDCAB = minimally invasive coronary artery bypass grafting; OPCAB = off-pump coronary artery bypass grafting; RR = risk ratio
O
ff-pump coronary artery bypass grafting (OPCAB) has evolved into a strategy that is complementary to on-pump coronary artery bypass grafting (CABG). However, patient selection for this procedure continues to generate interest. In the current era of coronary surgery, patients
From the Division of Cardiovascular Surgery, College of Medicine, Mayo Clinic, Rochester, Minn. Dr Zehr is now with the University of Pittsburgh Medical Center, Pittsburgh, Pa. Individual reprints of this article are not available. Address correspondence to Dumbor L. Ngaage, MBBS, at his current address: Department of Cardiothoracic Surgery, Castle Hill Hospital, Cottingham, East Yorkshire HU15 6JQ, United Kingdom (e-mail: [email protected]). © 2007 Mayo Foundation for Medical Education and Research
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frequently present for a reoperation in which revascularization using cardiopulmonary bypass is high risk. Although repeated coronary surgery by itself may no longer be considered high risk, sometimes patient characteristics and comorbidities escalate the risk of on-pump CABG reoperation.1-3 This subgroup of patients often presents a management dilemma. Alternative strategies of surgical revascularization, including OPCAB, have been explored in various subsets of these patients.4-10 Avoiding cardiopulmonary bypass has potential benefits,11,12 but concerns have been raised about the integrity of the coronary anastomosis on a beating heart and incomplete revascularization.13 Nonetheless, various studies have shown that OPCAB may have an added advantage in select groups of patients, including those who need reoperations,14-18 thereby emphasizing the importance of patient selection. However, data on late adverse outcomes, such as recurrent symptoms and cardiac events, are lacking. Although many studies have reported early results in different subsets of patients with specific comorbidities, few have investigated late results in high-risk patients defined by calculated surgical risks. The purpose of this study is to determine the role of OPCAB in the treatment of patients with severe, recurrent angina after CABG who are not suitable for percutaneous coronary intervention and are considered too high risk for conventional on-pump revascularization. Both the Parsonnet risk scoring system and the European System for Cardiac Operative Risk Evaluation (EuroSCORE) were used to identify patients with high predicted operative mortality.19-21 Operative outcome and late adverse events were evaluated to determine whether OPCAB is a viable alternative with durable results in this subset of patients. PATIENTS AND METHODS We used our institution’s cardiovascular surgery database to identify all patients who underwent repeated surgical myocardial revascularization with the off-pump technique because they were considered at high operative risk for repeated conventional on-pump CABG at our institution from March 4, 1994, through December 31, 2002. The Mayo Clinic Institutional Review Board approved this study in September 2003, and consent was obtained from
May 2007;82(5):567-571
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For personal use. Mass reproduce only with permission from Mayo Clinic Proceedings.
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all the patients. The operative risk of the patients was calculated using the Parsonnet multivariate logistic regression model and the additive EuroSCORE. All patients had an operative risk of 10 or greater by both risk-scoring systems. Twelve patients (14%) were denied repeated CABG at different facilities because of excessive surgical risk. Most of the patients had patent grafts from previous surgery and needed 1 or 2 grafts. The demographic characteristics, clinical symptoms, comorbidities, and perioperative details of the patients were collated by medical record review. SURGICAL TECHNIQUE The surgical access considered optimal for repeated revascularization was chosen for each patient on the basis of clinical profile and coronary angiographic findings. Therefore, operative approaches included limited thoracotomy incisions (minimally invasive coronary artery bypass grafting [MIDCAB]), full thoracotomy, and median sternotomy. Vessel stabilization was achieved by gentle snaring of target vessels with Silastic loops in the early period and later with local compression or suction devices. Visualization was facilitated by the use of carbon dioxide and isotonic sodium chloride solution blower systems. Distal and proximal anastomoses were handsewn in the usual fashion. FOLLOW-UP The Social Security Death Index was queried, and death certificates were obtained for all nonsurvivors. A follow-up survey questionnaire was sent to all survivors in March 2005 to investigate current symptoms, repeated cardiac interventions, repeated coronary angiograms, and cardiacrelated hospital readmissions. This was followed by telephone calls for a few nonresponders. Also, for patients who visited a Mayo Clinic facility for continued care, other follow-up information, such as postoperative angiography, stress echocardiography, and radionuclide viability studies, was retrieved from the Mayo Integrated Clinical System. STATISTICAL ANALYSES The primary end points were early or late death and repeated cardiac intervention. Categorical variables are expressed as percentages and continuous variables as the median and interquartile range, unless otherwise stated. Univariate analysis was performed using the χ2 test for categorical data, Wilcoxon rank sum test for continuous data, and Kaplan-Meier method for long-term outcomes. The proportional hazards model was used to identify variables associated with poor long-term survival. Models were constructed using categorical variables (sex, diabetes, renal failure, prior CABG, valve operation, myocardial infarction, history of heart failure, stroke, angina class, 568
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New York Heart Association class, preexisting atrial fibrillation, surgical priority, and chronic obstructive pulmonary disease) and continuous variables (age, body mass index, number of prior cardiac operations, left ventricular ejection fraction, Parsonnet score, and EuroSCORE). Statistical significance was defined as P<.05 with a 2-tailed test. Statistical analysis was performed using JMP Statistical Discovery Software (SAS Institute Inc, Cary, NC). RESULTS BASELINE AND OPERATIVE DETAILS Eighty-four patients with a median age of 69 years (range, 49-86 years) were included in the study; 14 (17%) were females. At the time of reoperation, all patients had severe recurrent angina (class III and IV). One patient (1%) had undergone heart transplantation previously, and 15 (18%) had more than 1 previous CABG operation. Preoperative coronary angiography revealed that the left internal thoracic artery was used as a bypass conduit in 60 patients (71%) but was patent in 43 (51%). All previous CABG operations were performed using cardiopulmonary bypass, and the median interval between the last CABG procedure and the reoperative OPCAB was 10 years (range, 0-35 years). The calculated median operative risk was 12 (range, 10-15) based on the EuroSCORE and 14 (range, 11-19) based on the Parsonnet multivariate logistic regression model. Thirty patients (36%) had a left ventricular ejection fraction of 40% or less. Table 1 outlines the baseline characteristics of the study population. MIDCAB incisions were used in 10 patients (12%), left thoracotomy in 26 (31%), and median sternotomy in 48 (57%). In most patients, arterial conduits were used, and the descending thoracic aorta was often the site for proximal anastomoses. Perioperative hemodynamic support was necessary with inotropes in 29 patients (35%), intra-aortic balloon pump in 12 (14%), and ventricular assist device in 2 (2%). One in-hospital death (1%) occurred. The operative details and outcome are outlined in Table 2. LATE OUTCOME Table 3 details the late clinical outcomes. The average duration of postoperative follow-up, defined as the mean interval between hospital discharge and the survey questionnaire, was 3.6 years (maximum, 9 years). During this period, 17 late postoperative deaths occurred, mainly from cardiac causes (12 patients). The Kaplan-Meier estimates for overall late mortality at 1, 3, and 5 years were 6% (95% confidence interval [CI], 3%-17%), 11% (95% CI, 5%22%), and 23% (95% CI, 10%-37%), respectively; Figure 1 shows the survival rates. Univariate determinants of poor long-term survival were body mass index (risk ratio [RR],
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OFF-PUMP CORONARY ARTERY BYPASS GRAFTING FOR HIGH-RISK REOPERATION
TABLE 1. Clinical Profile of 84 Patients Undergoing Repeated Off-Pump CABG*
TABLE 2. Perioperative Details of 84 Patients Undergoing Reoperations*
Characteristic
Value
Characteristic
Mean age (y) (IQR) Female Median body mass index (IQR) Presenting symptoms Angina class III IV Cardiogenic shock Cardiac morbidity Atrial fibrillation Myocardial infarction Median ejection fraction (%) (IQR) (n=80) Prior cardiac operation 1 previous CABG 2 previous CABGs Valve repair or replacements Heart transplantation LITA graft Not used Patent Stenosed Median interval from last operation (y) (IQR) Comorbidities Diabetes mellitus Renal failure Stroke Chronic obstructive pulmonary disease Peripheral vascular disease Median risk stratification values (IQR) Additive EuroSCORE Parsonnet multivariate logistic regression
69 (62-75) 14 (17) 28 (25-32)
Incision Median sternotomy Left thoracotomy Minimally invasive Vessel stabilization Snare Suction Compression No. of distal anastomosis 1 2 Site of distal anastomosis Left anterior descending artery territory† Circumflex territory† Right coronary artery territory Site of proximal anastomosis None Ascending aorta Descending aorta Nongraft arteries In situ grafts Arterial conduits Internal thoracic artery Left Right Bilateral Radial artery Surgical priority Elective Urgent Emergent Conversion to on-pump technique Perioperative cardiovascular support Inotropes Intra-aortic balloon pump Ventricular assist device Renal function impairment Stroke Operative mortality Median hospital length of stay (d) (IQR)
52 (62) 32 (38) 3 (4) 28 (33) 37 (44) 47 (35-60) 69 (82) 15 (18) 8 (10) 1 (1) 24 (29) 43 (51) 17 (20) 10 (6-15) 29 (35) 16 (19) 8 (10) 17 (20) 34 (40) 12 (10-15) 14 (11-19)
*Data are number (percentage) of patients unless otherwise indicated. CABG = coronary artery bypass grafting; EuroSCORE = European System for Cardiac Operative Risk Evaluation; IQR = interquartile range; LITA = left internal thoracic artery.
1.8; 95% CI, 1.7-2.0; P=.02), diabetes mellitus (RR, 1.5; 95% CI, 1.3-1.8; P=.003), chronic obstructive pulmonary disease (RR, 3.2; 95% CI, 1.1-10.5; P=.04), urgent or emergent surgery (RR, 4.1; 95% CI, 1.3-13.0; P=.05), EuroSCORE (RR, 1.3; 95% CI, 1.1-1.5; P=.002), and Parsonnet score (RR, 1.05; 95% CI, 1.01-1.08; P=.01). Nonfatal myocardial infarction was uncommon and occurred in 5 patients. Significant improvement in symptoms as measured by change in angina class (P<.001) and New York Heart Association functional class (P<.001) was experienced by patients at late follow-up as shown in Table 4. None of the patients had angina class IV symptoms, and only 10% had class III symptoms. Tests of graft patency were performed in 46 (70%) of the 66 surviving patients primarily to investigate symptoms. The indications for reinvestigations were (1) severe recurrent angina, (2) worsening dyspnea, (3) myocardial infarction, and (4) evaluation for noncardiac operation. Coronary angiography was performed in 25 patients, radioactive scanning in 17, and stress echocardiography in 4. Of Mayo Clin Proc.
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Value 48 (57) 26 (31) 10 (12) 9 (11) 24 (29) 51 (61) 67 (80) 17 (20) 48 (57) 35 (42) 14 (17) 25 (30) 18 (21) 29 (35) 3 (4) 9 (11) 37 (44) 21 (57) 12 (32) 4 (11) 20 (24) 53 (63) 29 (35) 2 (2) 1 (1) 29 (35) 12 (14) 2 (2) 9 (11) 3 (4) 1 (1) 6.5 (5-9)
*Data are number (percentage) of patients unless otherwise indicated. IQR = interquartile range. †Three patients had grafts to the left anterior descending and diagonal arteries (both left anterior descending territory), and 4 patients had grafts to 2 arteries in the circumflex territory.
the 25 patients with severe recurrent symptoms, postoperative coronary angiography revealed patent grafts in 19. DISCUSSION We found that OPCAB is a viable alternative strategy for repeated myocardial revascularization in patients not suitable for percutaneous intervention and at excessive operative risk for on-pump CABG. With selective use of this technique, and when appropriate in combination with MIDCAB incisions, we found a 90% reduction in the operative mortality predicted using conventional risk-scoring systems in this high-risk group of patients. Dewey et al15
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TABLE 3. Late Clinical Outcomes After Repeated Off-Pump Coronary Artery Bypass Grafting* Outcome
Value
Death Cardiac events observed Nonfatal myocardial infarction Death Overall late mortality (Kaplan-Meier estimates) (%) (95% CI) 1y 2y 3y Postoperative investigations (n=66) Coronary angiography Radioactive isotope scanning Stress echocardiography Status of graft(s) (n=25) Patent Occluded Angina class (n=53) I II III IV Medications (n=36) β-Blockers ACE inhibitors Aspirin Statin Warfarin Diuretic
17
100
Patients alive (%)
80
5 12 6 (3-17) 11 (5-22) 23 (10-37)
60
40
25 (38) 17 (26) 4 (6)
1-y survival: 94% 5-y survival: 77%
20
19 (76) 6 (24) 2
32 (60) 12 (23) 9 (17) 0 (0) 30 (83) 23 (64) 34 (94) 33 (92) 11 (31) 23 (64)
*Data are number (percentage) of patients unless otherwise indicated. ACE = angiotensin-converting enzyme; CI = confidence interval.
reported a similar finding using the Society of Thoracic Surgeons algorithm for predicted mortality. They reported a reduction in observed mortality in a subset of 153 patients who underwent repeated OPCAB compared with 279 who underwent on-pump CABG. The benefit of this strategy for high-risk reoperations is multifactorial. These patients often have some patent grafts and require target vessel revascularization; thus, incomplete revascularization is not a concern. Consequently, extensive dissection and mobilization for cannulation with the risk of iatrogenic injury are unnecessary. In addition, the deleterious effects of cardiopulmonary bypass are avoided, as are the problems of myocardial protection that can be challenging in these patients. Moreover, the selective use of limited incisions combines the advantages of MIDCAB with avoiding the cardiopulmonary bypass. Finally, the risk stratification systems designed for on-pump CABG may overestimate the risk of OPCAB.
4
6
Time after surgery (y) No. at risk 83
53
26
13
FIGURE 1. Kaplan-Meier survival curve of high-risk patients after offpump coronary artery bypass reoperation.
Major adverse cardiac events such as cardiac death, nonfatal myocardial infarction, and repeated cardiac intervention were not common in the long term. At 3, 5, and 7 years, respectively, the freedom from cardiac death was 98%, 83%, and 70%, and the overall survival times were 89% (95% CI, 77%-95%), 77% (95% CI, 63%-91%), and 67% (95% CI, 46%-81%). Even though these patients had significant comorbidities, the most common cause of late death was cardiac related. However, patient comorbidities such as diabetes and chronic obstructive pulmonary disease added an incremental effect on the risk of late mortality. Surgical risk stratification using the Parsonnet system and EuroSCORE captures patient characteristics and comorbidity and explains the association of a high-risk score with poor longterm survival. Graft patency after OPCAB has been questioned in the past, but Puskas et al22 showed that early patency rates were comparable to those after on-pump CABG for primary procedures. In patients undergoing repeated CABG, we know of no study that reports graft patency. In our select group of high-risk patients, we found a late patency rate of
TABLE 4. Pairwise Comparison of Preoperative and Postoperative Variables* Variables Mean angina class (n=53) Mean NYHA class (n=48) Mean EF (%) (n=43)
Preoperative
Postoperative
Difference (95% CI)
P value
3.2 3.4 46.6
1.4 1.7 45.4
1.8 (1.5 to 2.2) 1.7 (1.3 to 2.2) –1.2 (–5.6 to 3.2)
<.001 <.001 .60
*CI = confidence interval; EF = ejection fraction; NYHA = New York Heart Association.
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OFF-PUMP CORONARY ARTERY BYPASS GRAFTING FOR HIGH-RISK REOPERATION
76% in a subgroup reinvestigated for recurrent symptoms. Therefore, it is self-evident that this patency rate is an underestimation. The selection of patients with a greater propensity to graft occlusion for repeated angiography underpins the low late graft patency rate observed in this cohort of patients. Also, early postoperative angiography, which was performed to diagnose 5 of 6 occluded grafts, can be misleading, especially for arterial grafts. We previously reported the drawbacks of this procedure23 in a study that showed that 86% of grafts that were angiographically occluded in the early postoperative period were probe patent at immediate reoperation. Spasm of both the native coronary artery and arterial graft can be difficult to distinguish from true occlusion at angiography; thus, early postoperative angiography is an unreliable method to detect graft occlusion. The role of OPCAB in the management of coronary artery disease continues to be investigated. These data support the selective use of this technique in patients at high risk of reoperation and in combination with MIDCAB incisions when appropriate. This study examines the early and long-term clinical results in a group of patients with high predicted operative risk determined by objective and internationally accepted risk stratification systems used routinely in cardiac surgery. Other studies have defined high risk solely on the basis of specific comorbid disease conditions16,18,24 or complications of coronary artery disease25,26 or reoperation,7,27 but this study addresses a clinical dilemma increasingly encountered in practice: the patient with severe recurrent angina after CABG with patent graft(s) who requires 1 or 2 bypass grafts. Like all retrospective studies, our study has the inherent drawbacks of patient selection bias, recall bias, and incomplete data on some patients, but the active follow-up with a survey questionnaire provides supplementary data to offset some of these limitations. Because the study population was a highly select group, it was not possible to identify a similar group of patients who underwent on-pump CABG for comparison. However, the risk-scoring systems used in the study are reliable in predicting the operative result of conventional on-pump CABG. CONCLUSION Patients at excessive risk of reoperative CABG pose a management challenge. We found that OPCAB may be a suitable alternative in patients with an estimated risk of reoperation of 10% and higher who require 1 or 2 grafts. Its selective use can mitigate operative mortality with satisfactory late outcomes. We found a significant reduction in reoperative mortality with a low rate of major adverse cardiac events and acceptable long-term survival with the offpump technique combined with a tailored surgical access. Mayo Clin Proc.
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