Interact CardioVasc Thorac Surg 2008;7:218-221. doi:10.1510/icvts.2007.167916
© 2008 European Association of Cardio-Thoracic Surgery
Institutional report - Coronary |
Early and mid-term results of off-pump coronary artery bypass grafting in patients with end stage renal disease: surgical outcomes after achievement of complete revascularization
Tetsuya Horaia,*,
Toshihiro Fukuib,
Minoru Tabatac and
Shuichiro Takanashib
a Department of Biomedical Engineering, Lerner Research Institute, The Cleveland Clinic Foundation, 9500 Euclid Avenue, ND20, Cleveland, OH 44195, USA
b Department of Cardiovascular Surgery, Sakakibara Heart Institute, Tokyo, Japan
c Department of Cardiac Surgery, Brigham and Women's Hospital, Boston, MA, USA
Received 13 September 2007;
received in revised form 28 November 2007;
accepted 29 November 2007
 The abstract was presented at the 14th annual meeting of the Asian Society of Cardiovascular Surgery, Osaka, Japan, June 1–3, 2006.
*Corresponding author. Tel.: +1-216-445-9333; fax: +1-216-444-9198.
E-mail address: thourai-tky{at}umin.ac.jp (T. Horai).
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Abstract
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End stage renal disease is a risk factor for mortality after coronary artery bypass grafting. We conducted a retrospective review of 37 consecutive dialysis-dependent patients who underwent off-pump coronary artery bypass grafting between April 2001 and July 2004. Complete revascularization was successfully performed in all patients. The mean number of anastomoses was 3.7, and early graft patency was 98.8%. Thirty-day mortality was 2.7%. In-hospital mortality was 8.1%. At a mean follow-up of 26 months, there were six late deaths including one cardiac death, and five cardiac events. Actuarial survival rate at one and three years was 88.8% and 77.0%, respectively. Cardiac event free rate at one and three years was 85.9% and 72.6%, respectively. Multivariate analysis revealed that preoperative left ventricular ejection fraction (P=0.003) and smoking history (P=0.026) were significant predictors for mid-term mortality, and co-existing peripheral vascular disease was a significant predictor for cardiac events (P=0.033). Early and mid-term outcomes after off-pump coronary artery bypass grafting in patients with end stage renal disease have acceptable mortality rate with excellent early graft patency, while low ejection fraction and smoking history were significant risk factors for mid-term survival, and co-existing peripheral vascular disease was a significant predictor for cardiac events.
Key Words: Off-pump coronary artery bypass; Dialysis; Chronic renal insufficiency
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1. Introduction
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Cardiovascular disease remains the most frequent cause of death for patients with end stage renal disease (ESRD). More and more patients will be referred for surgical revascularization owing to angina or hemodynamic instability while on dialysis. ESRD is considered to be an independent risk factor for early and late survival after coronary artery bypass grafting (CABG) [1]. According to the large studies that enrolled more than 50 dialysis-dependent patients, operative mortality of 5.9–14.6% has been reported [1–6]. Off-pump CABG (OPCAB) has become an established and feasible procedure [7] and has been shown to reduce morbidities in high-risk patients [8]. However, early and late outcome of OPCAB in ESRD patients remains poorly defined. Some reports have demonstrated that OPCAB has better early outcomes than conventional CABG in ESRD patients [9]. Others have shown that ESRD does not increase operative risks in OPCAB [10, 11]. However, a recent study has shown that long-term survival after OPCAB was worse than that after conventional CABG because of less frequency of complete revascularization [12].
We performed complete surgical revascularization, which was defined as providing one or more grafts per any coronary system which had 50% or more stenotic lesions present, without cardiopulmonary bypass in patients with ESRD. In this study, we assessed early and mid-term outcomes in ESRD patients after OPCAB with complete revascularization and identified the predictors for postoperative death and cardiac events.
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2. Materials and methods
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2.1. Patients
We retrospectively reviewed 37 consecutive dialysis-dependent patients scheduled for OPCAB between April 2001 and July 2004 at the Shin-Tokyo Hospital, Chiba, Japan. Informed consents were obtained for patient's data collection and there were no ethical conflicts in this study. Of those patients, 36 were receiving hemodialysis and one was receiving peritoneal dialysis. All procedures were performed by a single, experienced surgeon (S.T.). This study group accounts for 6.0% of all OPCAB scheduled patients in the same period at the same hospital.
The patients' demographics are shown in Table 1. The most common cause of ESRD was diabetic nephropathy in this study group. Smoking history included current smoking history and past history within one year before surgery, and emergency surgery was defined as a non-elective operation performed within 24 h after admission. Co-existing peripheral vascular disease included a history of claudication, prior surgical or percutaneous treatment for arterial vascular insufficiency, and an ankle brachial index of 0.9 or less.
2.2. Surgical procedures
Our surgical procedures are as follows. Surgery was mostly performed through median sternotomy. Arterial conduits were harvested in a skeletonized fashion, and saphenous vein grafts were harvested with an open method. A heart positioner and stabilizer were used during anastomoses, and epiaortic echo was performed to evaluate the availability of the aorta. A bloodless field was obtained using a proximal silastic snare suture and CO2 blower. The indication for performing bypass grafting was 50% or more stenotic vessels larger than 1 mm in diameter.
2.3. Data collection and follow-up
We retrospectively reviewed the medical records. In addition, follow-up data were collected from telephone interviews with the patients or their family members.
Myocardial infarction was defined as a positive result for new Q-waves in the electrocardiogram, or a peak level of the myocardial-bound isoenzyme of creatine kinase 10% of total creatine kinase. Angina was diagnosed when typical symptoms accompanied with new ST and T-wave changes appeared on the electrocardiogram. Postoperative complications included the following: bleeding requiring re-exploration, myocardial infarction, low output syndrome (the use of dopamine or dobutamine at doses over 5 µg/kg/min), ventricular arrhythmia, stroke, respiratory failure (intubation time over 48 h), and mediastinitis. Cardiac events included cardiac death, recurrent angina, myocardial infarction, percutaneous coronary interventions and repeated CABG.
2.4. Statistical analysis
Values of continuous variables are expressed as mean±S.D. Univariate comparisons were performed using a Student's t-test,  2-test or Fisher's exact test. A logistic regression model was used to determine predictors of death and major postoperative complications. Explanatory variables in this model included all variables in Table 1 and harvest of bilateral internal mammary arteries. Actuarial survival rate, freedom from cardiac death and freedom from cardiac events were analyzed using the Kaplan–Meier method. Cox proportional hazard model was used to determine significant predictors for midterm mortality and cardiac events. Explanatory variables were selected with a forward stepwise method. The P-value was considered statistically significant when it was <0.05. Statistical analysis was performed using the SPSS version 11.5J (SPSS, Inc., Chicago, IL).
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3. Results
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Operative variables are listed in Table 2. One required emergency conversion for a cardiopulmonary bypass due to ventricular arrhythmia during anastomoses. Complete revascularization was successful in all patients. The left internal mammary artery (IMA) was the most frequently used graft, in 36 patients (97.3%). The right IMA, the gastroepiploic artery, and the saphenous vein graft were used in 29 patients (78.3%), 11 patients (29.7%), and 23 patients (62.2%), respectively. Bilateral IMAs were harvested in 29 patients (78.3%). The number of distal anastomoses was 3.7±1.2 (range 1–6).
Thirty-day mortality was 2.7% (1/37), and in-hospital mortality, including 30-day mortality, was 8.1% (3/37). Causes of death were ventricular arrhythmia, perioperative myocardial infarction, and respiratory failure associated with mediastinitis. Postoperative morbidities occurred in five patients (13.5%) as detailed in Table 3. Univariate analysis revealed that preoperative left ventricular ejection fraction was significantly associated with in-hospital mortality (P=0.002). However, the association was not significant in a multivariable logistic regression model. Any variables including preoperative and operative variables were not detected as a predictor for the occurrence of postoperative morbidities.
Postoperative angiography was performed in patients who gave informed consent. Thirty patients underwent coronary angiography within one month after surgery, and a total of 81 grafts were evaluated. The early graft patency rate was 98.8% as summarized in Table 4.
Follow-up was completed in 33 of 34 patients who were discharged from our hospital. Mean follow-up time was 26±15 months (range 5–54). No patients underwent kidney transplantation during the course of the follow-up. There were six late deaths, including one cardiac death of myocardial infarction 13 months after surgery. There were four other cardiac events during the follow-up period. All of them were diagnosed as angina, and new stenotic lesions or progressions of disease were found in the native coronary arteries, not in any bypass grafts, from angiography. Actuarial survival rates, including operative mortality, at one and three years were 88.8% and 77.0%, respectively. Freedom from cardiac death at one and three years was 94.4% and 91.1%, respectively. Cardiac event free rates at one and three years were 85.9% and 72.6%, respectively. Cox proportional hazard model revealed that preoperative left ventricular ejection fraction and smoking history were significant predictors for postoperative death, and it also revealed that co-existing peripheral vascular disease was a significant predictor for cardiac events as presented in Table 5.
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4. Discussion
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Atherosclerotic vascular disease including myocardial infarction and other cardiac disorder is the most frequent cause of morbidity and mortality in patients with ESRD. There are many reports regarding the outcomes after CABG in ESRD patients [1–6]. However, there are only some reports of OPCAB for ESRD patients, demonstrating early outcome advantages over conventional CABG [9] or demonstrating comparable results with non-dialysis patients undergoing OPCAB [10, 11]. On the other hand, Dewey and associates have shown that long-term survival after OPCAB was found to be worse than for a conventional CABG group because of less frequency of complete revascularization [12]. In most of these studies [9, 10, 12], OPCAB patients with ESRD received relatively few grafts and the numbers of distal anastmoses were smaller than those of on-pump or non-ESRD patients. It might lead to the occurrence of incomplete revascularization. Complete revascularization is one of the important goals of CABG to provide patients with good long-term functional status, and it should be performed whenever possible [13]. The OPCAB technique for multivessel complete revascularization is an established procedure [7], and this should be implemented for ESRD patients. In our patients, the number of distal anastomoses was 3.7±1.2 (range 1–6), which was larger than that of previous reports, and complete revascularization was carried out without cardiopulmonary bypass in all patients.
Our thirty-day mortality rate was 2.7%, and in-hospital mortality rate was 8.1%. Regarding remote outcomes, there was one cardiac death of myocardial infarction 13 months after surgery, and other causes were cerebral hemorrhage in three patients, pneumonia, and unknown. Three-year survival rates were reported to range from 56 to 90% in ESRD patients undergoing conventional CABG [2, 4–6]. Meanwhile, the follow-up period of OPCAB cohort in the previous study was relatively short [12]. In our study, freedom from cardiac death at three years was 91.1%, and there was only one cardiac death among those who survived operative period. Meanwhile, actuarial survival rate at three years was 77.0%, which is almost identical to those of previous studies. We believe that we were able to reduce the risk of fatal cardiac events with the indication of complete revascularization for ESRD patients. However, it did not necessarily improve the actuarial survival rate. Further investigation is expected to determine the best treatment of coronary disease in ESRD patients.
According to the previous reports, diabetes and peripheral vascular disease [5], or congestive heart failure and cardiomegaly [6], or age, left ventricular ejection fraction and NYHA classification [2] would be risk factors of remote mortality after CABG in ESRD patients. In this study, analysis of mid-term survival proved that smoking history was an independent predictor as well as preoperative left ventricular function. Franga and associates [14] stated the similar result in their study of on-pump CABG in dialysis-dependent patients. With these data, we should encourage our patients with ESRD to stop their smoking habit early.
There were five cardiac events in the follow-up period. Except for a patient who died of myocardial infarction, four patients underwent angiography that revealed the causes for cardiac events were progressions of disease in the native coronary arteries. Co-existing peripheral vascular disease was found to be the one and only significant predictor for cardiac events. This result would be convincible because arteriosclerosis has been considered to be a systemic disease.
To accomplish complete revascularization of multi-vessels, bilateral IMAs and SVG were frequently used in our patients, because the radial artery should be preserved for blood access to dialysis. Previous studies have shown that the use of bilateral IMAs in ESRD patients does not increase morbidity such as mediastinitis [3, 15]. The IMA is considered to provide an excellent patency rate as a coronary bypass graft. Moreover, arterial grafting was shown to reduce a risk of cardiac death in a long-term follow-up study [13]. Kai and associates also demonstrated that use of bilateral IMAs reduced cardiac events in their retrospective study [15]. In our study, harvesting bilateral IMAs did not lead to postoperative complications, and there was only one cardiac related death in the follow-up period. Although this issue is still controversial, we believe that the use of bilateral IMAs for complete revascularization of multi-vessels will provide many benefits even in ESRD patients.
The limitations of this study include the relatively short length of follow-up and small sample size, and our results may not be generalizable. A larger study is required to validate our results. Meanwhile, we cannot describe the superiority of complete revascularization as well as the OPCAB procedure because this was a retrospective observational study without a control group. A comparative prospective randomized trial is needed to determine the validity of them.
In conclusion, we were able to perform complete revascularization safely with off-pump techniques in ESRD patients, and early and mid-term outcomes have acceptable mortality rate with an excellent early graft patency rate. Use of bilateral IMAs did not increase the occurrence of postoperative morbidities, and we will continue to use bilateral IMAs for ESRD patients. We also determined that preoperative low ejection fraction and smoking history were significant predictors of mortality. Meanwhile, co-existing peripheral vascular disease was also demonstrated to be a significant predictor for cardiac events.
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Abstract
1. Introduction
