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European Journal of Cardio-thoracic Surgery 39 (2011) e122—e127 www.elsevier.com/locate/ejcts The influence of a low ejection fraction on long-term survival in systematic off-pump coronary artery bypass surgery§ Simon Maltais a, Martin Ladouceur b, Raymond Cartier a,* a Department of Cardiovascular Surgery, Montreal Heart Institute/Université de Montréal, Montreal, Quebec, Canada b Biostatistics Department, McGill University Health Center, Montreal, Quebec, Canada Received 19 August 2010; received in revised form 7 December 2010; accepted 13 December 2010 Abstract Objective: Poor left-ventricular ejection fraction (EF) is a recognized operative and long-term risk factor in coronary artery bypass surgery. Over the past decade, off-pump coronary artery bypass surgery has emerged as a new strategy to address myocardial revascularization in poor left-ventricular EF patients, but few reports have documented long-term results. The aim of this study was to investigate long-term clinical results in off-pump coronary artery bypass patients with 35% left-ventricular EF. Methods: From September 1996 to May 2006, 1250 patients underwent off-pump coronary artery bypass revascularization, and were prospectively followed-up at the Montreal Heart Institute. Among them, 137 patients (pts) had a preoperative left-ventricular EF 35%. Follow-up was completed in 97% of patients. Results: Mean follow-up was 66 34 months. Rate of grafts per pts was comparable in both groups. Overall 30-day mortality was 1.7% (1.5% EF >35% pts vs 2.9% in EF 35% pts; p = 0.19). Ten-year survival was lower in poor EF patients (44 7% vs 76 2%), and remained significant even after adjusting for risk factors ( p = 0.04). Freedom from cardiac death for both groups was also significantly reduced in poor EF patients ( p = 0.008). After adjustment, freedom from the combined end point of cardiac or sudden death, myocardial infarction, repeat coronary revascularization, unstable angina, and cardiac failure was comparable in both groups ( p = 0.5). Conclusions: Off-pump coronary artery bypass surgery can be performed adequately and safely in poor EF patients. However, overall and cardiac survival was decreased in this subset of patients with a comparable freedom from major cardiac adverse related events. # 2011 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved. Keywords: OPCAB; Left-ventricular dysfunction; Follow-up; Survival 1. Introduction Ischemic heart disease remains a leading cause of mortality in the developing countries [1]. There are currently more than 5 million diagnosed cases of congestive heart failure (CHF) in North America [1,2]. Recent estimates put the incidence at 550 000 new cases every year [3]. Currently, around 600 000 coronary artery bypass grafting (CABG) procedures are performed worldwide [1]. Conventional CABG using cardiopulmonary bypass (CPB) and cardioplegic arrest has been the gold standard to address ischemic heart disease for several decades. The on-pump CABG (ONCAB) strategy, combined with medical and anesthetic improvements, has ensured a low mortality despite an aging and sicker patient population. CABG among patients with reduced myocardial function still remains a daunting surgical challenge. Several studies have shown that patients with severely depressed § The senior author (R.C.) is advisor for CoroNéo. * Corresponding author. Address: Department of Cardiovascular Surgery, Institut de Cardiologie de Montréal, Université de Montréal, 5000 Belanger Street, Montreal, Quebec H1T 1C8, Canada. Tel.: +1 514 376 3330x2511; fax: +1 514 376 1355. E-mail address: [email protected] (R. Cartier). heart function should be considered high-risk surgical candidates compared with patients with normal ejection fraction [4—6]. In an attempt to reduce the potential deleterious effects of CPB, its avoidance has emerged over the past few years as a new strategy to address myocardial revascularization [7—9]. There have been several controversies surrounding the choice of the optimal surgical strategy in patients with reduced ejection fraction. Many surgeons prefer using CPB because hemodynamic instability, hypotension induced by ventricular arrhythmias, or cardiac arrests are frequent problems encountered in this specific group of patients. However, it has been speculated that extracorporeal circulation could exacerbate myocardial damage in patients with compromised left ventricles. This could be partly related to the activation of inflammatory mediators, the nonphysiologic ventricular geometry of the empty heart during CPB, or the reduced function of the interventricular septum following CPB [10,11]. There are therefore few reports addressing the long-term evolution of off-pump CABG (OPCAB) revascularization in patients with reduced (<35%) ejection fraction. The objective of this study was to analyze systematically the 1010-7940/$ — see front matter # 2011 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.ejcts.2010.12.022 S. Maltais et al. / European Journal of Cardio-thoracic Surgery 39 (2011) e122—e127 long-term results of OPCAB surgery in a large contemporary cohort of patients with a reduced ejection fraction, focusing specifically on the survival, and on the occurrence of major cardiac-related events in this specific population. 2. Method 2.1. Study design This is a retrospective analysis of prospectively gathered data over a 10-year period (mean follow-up, 66 34 months). From September 1996 to May 2006, 1250 patients underwent OPCAB revascularization at the Montreal Heart Institute (Montreal, Quebec, Canada). From this group, 14 patients had no preoperative left-ventricular ejection fraction (LVEF) evaluation and were excluded from the study. This is a single-surgeon experience (R.C.), and this series represents over 97% of all cases of revascularization performed during the same period. Among patients undergoing OPCAB surgery during this time interval, 137 patients (12%) had a preoperative LVEF of 35% or less, as calculated using transthoracic echocardiogram (TTE), ventriculography or nuclear imaging. Twelve months’ follow-up was completed in all patients. Over time, only 3% of the patients were lost in follow-up. Follow-up reports were obtained by routine clinic visit, telephone interview, or directly from the family physician. When the patients were rehospitalized for cardiac causes in a different hospital, hospitalization reports were requested. This study was approved by the Review Board of the Montreal Heart Institute, and individual consent was obtained for all patients included in this study. 2.2. Surgical technique Patients were operated under general endotracheal anesthesia using continuous Swan—Ganz catheter monitoring, transesophageal echocardiography and arterial pressure monitoring. As previously described, the surgical technique used has been relatively consistent through the years [12]. Patients with important preoperative hemodynamic instability, or moderate to severe (3+ to 4+) mitral regurgitation were excluded from this study, as they were operated under CPB. Most of the surgeries were performed using a full sternotomy incision. During the first period of the experience, the left internal thoracic artery (ITA) was harvested using a pedicled technique. Since 2000, almost all patients had their ITA skeletonized. Heparin was administered at a dose of 150 KIU kg 1. A compressiontype device (Cor-Vasc Retractor Stabilizer; CoroNéo, Montreal, Quebec, Canada) was used for all cases to allow adequate coronary stabilization. In most instances, the culprit lesion was bypassed first. All proximal venous anastomoses were performed with a single side-bite clamping of the ascending aorta while maintaining a systemic blood pressure lower than 85 mmHg to lower the risk of aortic trauma. Postoperatively, all patients received aspirin (80 mg, daily), subcutaneous heparin (5000 KIU, three times a day), and, since 2002, clopidogrel (75 mg, daily) for the first 3 months. e123 2.3. Definition of terms All data included in this study were systematically and prospectively gathered. Patients with a low LVEF were defined as patients with an EF equal or lower than 35%. Perioperative myocardial infarction (MI) was considered significant when there was a new Q wave on the electrocardiogram in association with a new wall motion abnormality on postoperative echocardiography or myocardialspecific creatinine kinase (CK-MB) levels greater than 100 ng ml 1. Significant postoperative renal insufficiency was defined as an increase of 50 nm in creatinine levels at any moment in the postoperative period. Major adverse cardiac events were defined as a combined end point that included cardiac or sudden death, and rehospitalization for MI, repeated coronary revascularization, recurrent unstable angina, or congestive heart failure. 2.4. Statistical analysis Results are expressed as the mean value standard deviation. The t-test or linear regression was used to analyze continuous measures, while the chi-square test was used to analyze categorical data. All survival curves analyses are adjusted. The performed survival analyses were adjusted for potential confounders. Time to mortality or major adverse cardiac events were presented using adjusted survival curves and compared between groups (low vs normal LVEF) using the log-rank test. Cox regression analysis was used to predict the Table 1. Demographic characteristics. Number Age (years) Female Hypertension Diabetes Family history for coronary disease Hyperlipidemia Obesity Smoking Chronic pulmonary obstructive disease Chronic renal failure Peripheral vascular disease Stroke history Previous MI Recent MI (<30 days) NYHA class III or IV History congestive heart failure Left-ventricular ejection fraction (%) Preoperative atrial fibrillation Unstable angina Emergent operation Preoperative intra-aortic balloon No. affected vessels Left main disease Low LVEF (<35%) Normal LVEF (35%) 137 65.4 10.0 27 (19.7%) 76 (55.5%) 49 (35.8%) 79 (57.7%) 1099 64.4 10.0 230 (21.0%) 645 (58.6%) 318 (29.0%) 742 (67.5%) 100 37 48 27 (73.0%) (27.0%) (35.0%) (19.7%) 12 (8.8%) 46 (33.6%) 19 88 63 135 51 (13.9%) (64.2%) (46.0%) (98.0%) (37.%) 856 358 294 128 (77.8%) (32.5%) (26.7%) (11.8%) 47 (4.3%) 199 (18.1%) 0.28 0.41 0.27 0.12 0.15 0.12 0.11 0.02 0.01 0.02 <0.0001 (7.6%) (34.6%) (17.3%) (99.1%) (4.7%) 0.01 <0.0001 <0.0001 0.68 <0.0001 29.2 5.3 55.6 9.7 <0.0001 11 (8.0%) 37 (3.4%) 0.01 113 (82.5%) 26 (11.0%) 33 (24.1%) 750 (86.9%) 45 (4.1%) 56 (5.1%) 0.01 <0.0001 <0.0001 2.74 0.51 47 (34.3%) 84 381 190 1091 52 p Value 2.67 0.57 325 (29.5%) 0.20 0.15 LVEF: left-ventricular ejection fraction; MI: myocardial infarction; NYHA: New York Heart Association. e124 S. Maltais et al. / European Journal of Cardio-thoracic Surgery 39 (2011) e122—e127 effect of a low (35%) EF on mortality and on major adverse cardiac events adjusted for the risks factors that were significant at a 0.05 level in the univariate analysis. Actuarial survival was obtained using the Kaplan—Meier method. Statistical significance was considered at a value of p < 0.05. Data were analyzed using the Statistical Package for Social Sciences (SPSS) 13.0 software (SPSS, Chicago, IL, USA). 3. Results 3.1. Demographic characteristics and preoperative risk factors Table 1 reports preoperative demographic characteristics of all patients included in this study. As expected, patients in the low LVEF group were generally burdened with more comorbidities than patients in the normal LVEF group. Smoking, chronic pulmonary obstructive disease, chronic renal failure, peripheral vascular disease, stroke history, atrial fibrillation, previous MI (including recent MI), and history of CHF were significantly more frequent in the low LVEF group. Similarly, patients in the low LVEF group had more unstable angina, had more frequently emergent operations, and had an increased rate of preoperative intra-aortic balloon pump insertion. 3.2. Operative data Surgical and operative details are reported in Table 2. The only statistically significant difference was the percentage of bilateral ITA bypasses performed, which was significantly lower in the low LVEF group (16.9% vs 31.9%; p < 0.0001). As expected, completeness of revascularization was significantly lower in the low LVEF group ( p < 0.001), as akinetic or dyskinetic territories are more frequently encountered in this subset of patients. The number of grafts performed was, however, similar between the two groups (low LVEF group, 3.09 0.87 vs 3.17 0.91 in the normal LVEF group, p = 0.29). No significant differences were observed for conversion to CPB. 3.3. Early postoperative outcomes Perioperative morbidity and in-hospital mortality (30 days) are represented in Table 3. There were no statistically significant differences in early in-hospital mortality (low LVEF group, 2.9% vs 1.5% in the normal LVEF group, p = 0.19). Table 3. Postoperative data. In-hopital/30-days mortality Perioperative MI Perioperative NSTEMI Confusion Reoperation for bleeding Atrial fibrillation Acute renal failure Stroke Transient ischemic attack Deep sternal infection Sternal dehiscence Respiratory complications Postoperative intra-aortic balloon ICU stay (days) Mechanical ventilation (h) Hospital stay (days) Low LVEF (<35%) Normal LVEF (35%) p Value 4 3 1 24 7 52 33 1 0 4 0 14 3 16 19 13 131 49 281 303 9 1 8 14 87 7 (1.5%) (1.7%) (1.2%) (11.9%) (4.5%) (25.6%) (27.5%) (0,8%) (0.3%) (0.7%) (1.3%) (7.9%) (0.6%) 0.19 0.45 0.53 0.05 0.43 0.002 0.24 0.69 0.54 0.04 0.19 0.22 0.09 2.6 0.8 16.8 1.0 6.5 0.5 0.001 0.01 0.10 (2.9%) (2.2%) (0.7%) (17.5%) (5.1%) (38.0%) (24.2%) (0,7%) (0%) (2.9%) (0%) (10.2%) (2.2%) 3.7 0.9 25.9 4.4 7.5 0.5 ICU: intensive care unit; LVEF: left-ventricular ejection fraction; MI: myocardial infarction; NSTEMI: non-ST-elevation myocardial infarction. There were no significant differences in neurological events, postoperative infarction, re-operations for excessive bleeding, acute renal failure, sternal dehiscence, respiratory complications, or insertion of postoperative intra-aortic balloon pump. Postoperative confusion, atrial fibrillation, and deep sternal infections were more frequently encountered in the low LVEF group. Intensive care unit length of stay was significantly increased in the low LVEF group (3.7 0.3 days vs 2.6 0.1 days, p = 0.001). The hospital length of stay was, however, similar for both groups (low LVEF group, 7.5 0.5 days vs 6.5 0.5 in the normal LVEF group, p = 0.10). 3.4. Late clinical outcomes 3.4.1. Long-term survival Non-adjusted 10-year survival was significantly lower in the low LVEF patients (44 7% vs 76 2%, p < 0.001), and remained significant even after adjusting for risk factors ( p = 0.04) (Fig. 1). Similarly, the adjusted freedom from cardiac death (defined as death from cardiac or unknown causes) survival curve was significantly reduced in the low LVEF group compared with the normal LVEF patients ( p = 0.008) (Fig. 2). The multivariate Cox regression analysis model revealed that preoperative CHF, chronic peripheral vascular disease, stroke history, recent MI, renal insufficiency, completeness of revascularization, and low LVEF (<35%) were significant predictors of long-term mortality (Table 4). Table 2. Operative data. Table 4. Multivariate Cox regression analysis model for overall survival. Re-operations No. of CABG Complete revascularization Conversion CPB Single ITA Bilateral ITA Sequential ITA Low LVEF (<35%) Normal LVEF (35%) p Value 8 (5.8%) 3.09 0.87 113 (83.1%) 2 (1.5%) 134 (97.8%) 23 (16.9%) 24 (18.0%) 71 (6.5%) 3.17 0.91 1047 (95.3%) 5 (0.5%) 1062 (96.7%) 351 (31.9%) 221 (20.1%) 0.48 0.29 <0.0001 0.17 0.41 <0.0001 0.45 CABG: coronary artery bypass graft; CPB: cardiopulmonary bypass; ITA: internal thoracic artery; LVEF: left-ventricular ejection fraction. Peripheral vascular disease Chronic renal insufficiency Completeness of revascularization Stroke history Recent myocardial infarction History congestive heart failure Preoperative low LVEF (<35%) Hazard ratio (HR) 95% CI p Value 1.78 2.29 0.50 1.96 1.55 1.63 1.46 1.31—2.43 1.46—3.61 0.33—0.77 1.34—2.88 1.12—2.15 1.09—2.46 1.00—2.15 <0.0001 <0.0001 0.002 0.001 0.01 0.01 0.04 CI: confidence interval; LVEF: left-ventricular ejection fraction. [()TD$FIG] [()TD$FIG] S. Maltais et al. / European Journal of Cardio-thoracic Surgery 39 (2011) e122—e127 Fig. 1. Survival curve comparing patients with low ejection fraction (<35%) (dashed line) and normal ejection fraction (solid line) after correcting for risk factors. Ten-year survival was significantly lower in the low LVEF patients after adjustment for risk factors ( p = 0.04). 3.4.2. Major adverse cardiac events (MACE)-free survival MACE-free 10-year survival was significantly decreased in low LVEF patients (60 8% vs 75 2%, p = 0.0002). However, after adjustments for significant variables, difference was not significant anymore (Fig. 3). After breaking down the major cardiac events, freedom from re-admission for CHF was less frequently encountered in low LVEF patients (82 5% vs 95 1%, p < 0.001), and remained significant even after correction for risk factors ( p = 0.03). 4. Discussion Considering the enormous growth of interventional cardiology in the recent years, patients undergoing CABG surgery are frequently encountered at the end stage of their disease, presenting with severely impaired LV function. [()TD$FIG]Despite many advances and innovations in cardiac surgery, Fig. 2. Freedom from cardiac death survival curve comparing patients with low ejection fraction (<35%) (dashed line) and normal ejection fraction (solid line) after correcting for risk factors. Ten-year cardiac-free survival was significantly lower in the low LVEF patients after adjustment for risk factors ( p = 0.008). e125 Fig. 3. Major adverse cardiac event-free survival curve comparing patients with low ejection fraction (<35%) (dashed line) and normal ejection fraction (solid line) after correcting for risk factors. Ten-year freedom from major adverse cardiac events (MACE) combining endpoint of myocardial infarction, repeat coronary revascularization, unstable angina, and cardiac failure was comparable for both groups ( p = 0.48). the management of patients with impaired LV function still remains a surgical challenge. Conventional surgical revascularization using CPB in patients with severely depressed LV function is associated with a higher postoperative morbidity and mortality compared with patients with normal LV function [13,14]. Good mid-term surgical results reported with OPCAB surgery were associated with an increased popularity of this revascularization technique, especially in this category of high-risk patients with poor LV function [15,16]. Several meta-analyses have been conducted to address outcomes of revascularization with/without CPB. Generally, patients undergoing OPCAB have at least equivalent outcomes with respect to perioperative mortality, stroke, atrial fibrillation, need for blood transfusions, and hospital length of stay [17—20]. The main focus of this retrospective study was to evaluate systematically the long-term evolution of OPCAB surgery in a large contemporary cohort of patients with a significantly depressed EF. The present study has several unique features compared with already published studies: (1) the series comprised a large number of patients with a significantly longer follow-up; (2) this study focused not only on survival, but also addressed the occurrence of major cardiac-related events in this specific population; (3) the number of grafts performed was comparable between the two groups; and (4) the surgical technique has been consistent through the years, and has been extensively described in previously reported studies [12]. In the current study, 1250 patients underwent OPCAB revascularization and were prospectively followed over 10 years. Among them, 137 patients had a preoperative LVEF of 35% or less. As expected for this much sicker population, patients in the low LVEF group were more likely to have significant history of smoking, chronic pulmonary obstructive disease, chronic renal failure, peripheral vascular disease, stroke, atrial fibrillation, previous MI, CHF, unstable angina, and preoperative intra-aortic balloon pump insertion than the normal LVEF group. Nevertheless, the in-hospital (30 e126 S. Maltais et al. / European Journal of Cardio-thoracic Surgery 39 (2011) e122—e127 days) mortality was non-significantly different between the two groups (low LVEF group, 2.9% vs 1.5% in the normal LVEF group, p = 0.19), although an unfavorable trend was observed for low EF patients. These results are comparable with two recent studies addressing OPCAB surgery in patients with reduced LV function (defined as LVEF lower than 35%) [21,22]. Both revealed similar results as regards perioperative morbidity (respiratory failure rate, inotrope use, and need for intra-aortic balloon counterpulsation, although Darwazah et al. reported higher in-hospital 30-days mortality (6.1%) in patients with severely depressed LVEF. This report showed, as expected, that the long-term survival rate in patients low LVEF was significantly lower than in patients with normal LV function. This difference remained significant even after adjusting for risk factors ( p = 0.04). Corrected freedom from cardiac death survival curve was also significantly reduced in the low LVEF group compared with the normal LVEF patients ( p = 0.008). As expected, cardiac-related death was more frequent in the low LVEF group (16.5% (n = 22), compared with the normal LVEF group (4.3%, n = 46); p < 0.001). Death from non-cardiac causes was similar between the two groups (15.5%, n = 21) in the low LVEF group, compared with 10.2% (n = 112) in the normal LVEF group ( p = 0.13). Youn et al. showed similar midterm results in patients with depressed LV function as OPCAB revascularization resulted in a survival rate of over 80% at 6 years [23]. Suzuki et al. recently reported comparable midterm results, as the 5-year freedom from death from all causes was 57% in an OPCAB group of patients with a low LVEF. In this same study, the rates of freedom from cardiac death observed was 73%, while the rates of freedom from the combined end point of cardiac death, MI, repeat coronary intervention, and heart failure requiring treatment was 65% [24]. In our experience, the corrected freedom from major adverse cardiac events (MACE) combining end point of MI, sudden death, repeated coronary revascularization, unstable angina, and cardiac failure was comparable for both groups ( p = 0.48). However, when taken separately, corrected CHF-free survival was significantly lower in 35% of LVEF patients (Table 5). This emphasizes the need for a close postoperative medical follow-up in organized CHF clinics for this specific group of patients. Aggressive heart failure therapy (beta-blockers, angiotensin-converting enzyme (ACE)-inhibitors) should always be rapidly reinstituted following surgery in this high-risk group of patients. From a technical perspective, achieving good surgical outcomes among patients with compromised LV results from the ability to completely revascularize the ischemic myocardium. OPCAB revascularization of the diseased coronary vessels can only be done under optimum conditions, provided the quality of vessels is suitable for grafting. In this Table 5. Freedom from major adverse cardiac events (%) at 10 years according to each endpoints. Freedom from: Low LVEF (<35%) Normal LVEF (35%) p Value Recurrent myocardial infarction Recurrent angina Repeated angiogram Repeated revascularization Congestive heart failure 96 2% 89 3% 75 6% 93 3% 83 2% 93 1% 84 2% 76 2% 90 1% 95 2% 0.72 0.79 0.60 0.60 0.001 retrospective study, the number of grafts performed did not differ between the two groups. To perform a complete revascularization in OPCAB surgery, the heart must be elevated. Previous work by Grundeman et al. showed that coronary blood, especially in the circumflex system, is greatly affected by vertical displacement [25]. We believe that minimizing hemodynamic changes by using the Trendelenburg position, deep pericardial traction stitches, coronary shunts, and, occasionally, the right pleuro-pericardial detachment is the key to achieve optimal revascularization in this group of high-risk patients with depressed LV function. In the present study, severe persistent hemodynamic instability or intractable signs of ongoing ischemia, despite these simple maneuvers, were the most frequent reasons for conversions. 5. Conclusions There are few reports addressing the long-term evolution of OPCAB revascularization in patients with a depressed LV function. The current study showed that OPCAB surgery could be performed adequately and safely in poor EF patients. However, overall and cardiac survival was decreased, while a comparable freedom of major cardiac adverse related events was observed. 6. Limitations This study is limited by its retrospective design. Despite advanced statistical methodology, unknown sources of bias may possibly confound these results. Seven patients were also converted intra-operatively from OPCAB to CPB. However, the incidence of conversion was very low (0.6%) and not significantly different between the two groups. 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