Asian Cardiovasc Thorac Ann 2007;15:19-23
© 2007 Asia Publishing EXchange Ltd
Risk Evaluation and Midterm Outcome of Cardiac Surgery in Patients on Dialysis
Noriko Boku, MD,
Munetaka Masuda, MD,
Masataka Eto, MD,
Takahiro Nishida, MD,
Shigeki Morita, MD,
Ryuji Tominaga, MD
Department of Cardiovascular Surgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
For reprint information contact: Munetaka Masuda, MD Tel: 81 45 787 2644 Fax: 81 45 786 0226 Email: mmasuda{at}yokohama-cu.ac.jp, Department of Surgery, Graduate School of Medicine, Yokohama City University, 3-9, Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan.
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ABSTRACT
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The medical charts of 54 patients on maintenance dialysis who underwent cardiovascular surgery (37 elective and 17 urgent/emergency) from 1994 to 2004 were retrospectively analyzed. Thirty patients had coronary artery bypass grafting (17 elective and 13 urgent/emergency), 18 had valve replacement (16 elective and 2 urgent/emergency), and 6 underwent aortic surgery (4 elective and 2 urgent/emergency). The overall early mortality rate was 11.1%, comprising 2 patients (5.4%) who had elective operations and 4 (23.5%) who had urgent or emergency operations ( p = 0.049). The overall 5-year survival rate was 48.4%. The 5-year survival rate was 67.2% for elective surgery and 10.5% for urgent/emergency surgery ( p = 0.0001). The midterm clinical results after elective cardiovascular surgery were acceptable, whereas the results after urgent/emergency surgery were poor. For elective surgery, sufficient and detailed preoperative examinations might have contributed to the better operative outcome. Early diagnosis and consultation to avoid urgent/emergency operations in dialysis patients is recommended.
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INTRODUCTION
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Cardiovascular disease is a leading cause of mortality in patients requiring maintenance dialysis.1,2 In 2000 and 2001, more than 30% of patients on maintenance dialysis in Japan died from heart failure or myocardial infarction.3 Although the reported number of patients on maintenance dialysis who undergo cardiac surgery has been increasing, the results have not been satisfactory.4–8 End-stage renal failure requiring renal replacement therapy is generally recognized as one of the major risk factors for mortality after cardiovascular surgery.9,10 In addition, the prognosis of patients after inception of maintenance dialysis is poor, and the mortality rate for cardiovascular events such as coronary artery disease and congestive heart failure in dialysis patients is more than 10 to 20 times higher than in the general population.1,2 There are several recent reports on the outcomes of cardiac surgery, which included a large number of dialysis patients.4,5 The aim of the present study was to analyze the operative outcome in patients on maintenance dialysis in our institute and to stratify the operative risk in these patients, using logistic EuroSCORE to predict midterm results.
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PATIENTS AND METHODS
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From January 1994 to December 2004, 2,274 cardiovascular operations were performed in Kyushu University Hospital, including 54 patients on maintenance dialysis. There were 37 elective and 17 urgent or emergency operations. The medical charts of these patients were retrospectively analyzed, and data on their present status were collected through outpatient records, telephone interviews, and letters. Operative risk was estimated by calculating the logistic EuroSCORE for each patient.11
Prior to the operation, patients underwent brain computed tomography and carotid artery Doppler ultrasound examination to evaluate cerebrovascular disease. When there was doubt about the presence of a significant lesion in the cervical or intracranial arteries, patients subsequently underwent cerebrovascular scintigraphy and magnetic resonance angiography. Most patients also underwent chest computed tomography to evaluate calcification in the ascending aorta. Epiaortic echocardiography was carried out after pericardiotomy in all patients who underwent surgery after 1999, and the operative strategy for coronary artery bypass grafting (CABG) was modified, or the site of aortic cross clamping was altered, to avoid complications due to atheromatous thromboembolism. The indications for off-pump coronary artery bypass were based on past history and findings obtained from the preoperative examinations and intraoperative epiaortic echo. The indication for on-pump beating heart CABG was hemodynamic instability in patients who were not candidates for aortic cross clamping due to poor preoperative cardiac function and significant atheromatous lesions in the ascending aorta.
In off-pump coronary artery bypass, coronary anastomoses were performed using a suction-type stabilizer and an apical suction device, with or without a coronary shunt. Conventional CABG, valve surgery, and distal aortic operations were performed under cardiopulmonary bypass with moderate systemic hypothermia. These patients received cold crystalloid cardioplegia every 20 min and terminal warm blood cardioplegia just before aortic declamping for cardioprotection, which was the same as the method used in the non-dialysis patients. The patients also had intraoperative diluted ultra-hemofiltration during cardiopulmonary bypass, until the serum potassium levels declined below 4.0 mEq·L–1. Circulatory arrest and retrograde cerebral perfusion under deep hypothermia were employed in aortic arch operations. Patients who underwent elective surgery were dialyzed on the day before the operation. Postoperative dialysis was initiated with continuous hemofiltration on the day after the operation in the intensive care unit after confirmation of hemostasis. The method of hemodialysis was switched to the usual dialysis when the patient’s hemodynamics stabilized.
The chi-squared test or Fischer’s exact test was used for analyses of categorical data, and an unpaired t test was used for analyses of continuous parameters. Survival analyses were performed with the Kaplan-Meier method to determine the actuarial survival. Survival rates were compared between patient groups with the log rank test.
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RESULTS
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There were no females among the urgent/emergency patients. There was no significant difference in the mean ages of the elective and urgent/emergency groups, nor in the frequencies of comorbidity (Table 1
). The mean logistic EuroSCORE in patients who underwent urgent/emergency surgery was significantly higher than in those who had elective operations ( p = 0.002). The predicted mortality calculated by logistic EuroSCORE for each category of disease was 8.75 for ischemic heart disease, 11.2 for valvular heart disease, and 13.2 for aortic disease (Table 1).
The operation time, duration of cardiopulmonary bypass, and aortic cross clamp times were 505 ± 261, 208 ± 93, and 104 ± 44 min, respectively, in elective surgery. In urgent/emergency operations, these times were 487 ± 153, 192 ± 59, and 111 ± 43 min, respectively. The surgical procedures are summarized in Table 2. In 27 of the 30 CABG cases (90%), the left internal thoracic artery was used; in the other 3 cases, this conduit had already been used in a previous operation. Eighty percent of CABG operations were performed with arterial grafts only (14 of 17 elective cases, 10 of 13 urgent/emergency cases). The mean number of distal anastomoses was 2.2 ± 1.1 in elective operations and 2.8 ± 1.0 in urgent/emergency procedures. After the introduction of routine intraoperative epiaortic echo in 1999, the percentage of off-pump operations in elective CABG significantly increased (0/10 before 1999, 3/7 after 2000; p = 0.023). Mechanical valves were our prostheses of choice although a bioprosthetic valve was used in 4 patients, based on patient preference.
Early mortality is shown in Table 3. The overall early mortality was 6 patients (11.1%); 2 had elective operations and 4 had urgent/emergency operations. The early mortality rate was significantly higher in the urgent/emergency group (23.5%) compared to the elective group (5.4%; p = 0.049). The causes of the 2 early deaths after elective surgery were systemic arterial thromboembolism after aortic valve replacement, and gastrointestinal bleeding after conventional CABG. Two operative deaths among the urgent/emergency group were due to acute mesenteric arterial thromboembolism after emergency off-pump CABG, and multiple organ failure resulting from low cardiac output syndrome after urgent mitral valve replacement for active infective endocarditis. The causes of the 2 hospital deaths in the urgent/emergency group were intraoperative stroke after ruptured descending aortic aneurysm repair, and massive intestinal bleeding after emergency ascending aortic replacement. Perioperative morbidity is shown in Table 3. The frequency of mediastinitis was significantly higher in the urgent/emergency group ( p = 0.033). The incidence of prolonged mechanical ventilation (> 72 hr) was also significantly higher in the urgent/emergency group (52.9%) compared to the elective group (21.6%; p = 0.021).
The follow-up was 100% complete. The mean follow-up period was 5.54 years (range, 0.02–11.04 years). The overall 1 and 5-year survival rates were 73.4% and 48.4%, respectively. The survival curves are shown in Figure 1. The 1 and 5-year survival rates in patients treated electively were 84.8% and 67.2%, respectively, whereas the 1 and 5-year survival rates in the urgent/emergency group were 50.4% and 10.5%, respectively (Figure 1). There was a significant inter-group difference in survival rates ( p = 0.0001). The 1 and 5-year survival rates including operative deaths in CABG patients were 77.9% and 47.2%. The 5-year survival including operative deaths in elective CABG patients was 70.8%. The 5-year survival including operative deaths in elective valve surgery was 49.2%. All 4 patients who had elective aortic surgery survived. The 5-year survival including operative deaths in urgent/emergency CABG patients was 14.0%. There were no survivors among patients who underwent urgent/emergency valve and aortic surgery. The causes of late mortality are also included in Table 3
. Five deaths in CABG patients and 1 in a valve surgery patient were cardiac-related. Five deaths in CABG patients and 2 in valve surgery patients were due to infectious diseases. Other late morbidity included catheter intervention in 2 CABG patients and cerebral hemorrhage in one who had a valve replacement.
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DISCUSSION
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The major finding of this study was that both early and late mortality rates were significantly higher in patients treated on an urgent or emergency basis. The 5-year survival after elective surgery of 67.2% is better than the overall 5-year survival after inception of dialysis in Japan (58%–63%).3 End-stage renal failure is generally considered to be one of the major risk factors for mortality after cardiac operations.9,10 The predicted operative mortality calculated by logistic EuroSCORE in our patients was relatively high in the elective surgery patients (6.8%) and very high in urgent/emergency patients (16.9%). Our actual mortality was comparable to the predicted values. Therefore, risk stratification by logistic EuroSCORE was a useful predictor in the current study. We also compared these scores with recent non-dialyzed CABG patients in our institute. There were 380 elective and 184 urgent/emergency CABG operations. The early mortality in elective CABG was 0.26% and the logistic EuroSCORE was 3.43 ± 2.98, whereas the early mortality was 1.63% and the logistic EuroSCORE was 14.18 ± 13.81 in urgent/emergency CABG in non-dialyzed patients. There was no significant difference in logistic EuroSCOREs between dialyzed and non-dialyzed CABG patients. Accordingly, the early mortality in dialyzed patients was higher than in non-dialyzed patients with an equivalent logistic EuroSCORE; however, midterm survival in elective CABG patients was better than that in dialyzed patients in general.2
High operative morbidity in dialyzed patients is an important problem that needs resolution. The high rates of thromboembolism and bleeding are of major concern. To reduce the incidence of thromboembolism, we introduced vigorous assessment of vascular disease, including the use of epiaortic echo. Since this was introduced in 1999, intraoperative stroke has become a rare complication, although we need more cases to draw definitive conclusions. It is well known that dialyzed patients with cardiovascular diseases or congestive heart failure have unfavorable prognoses.1,2,12 Although our results showed a satisfactory 5-year survival in elective surgery patients, it was disappointing (10.5%) in the urgent/ emergency patients. This implies additional risk factors in the urgent/emergency patients due to comorbidity. The logistic EuroSCORE seemed to be a good predictor not only of early outcome but also of late outcome.
The reported 5-year survival after CABG in patients on dialysis is 39% to 71%, whereas the 5-year survival after valve replacement in this group is 
= 20%.4–6,13–15 Our survival results were superior for valve replacement and comparable for CABG. Our good results for valve replacement may be due to the fact that most valve operations were isolated aortic valve replacements or aortic valve replacement with a small additional procedure.4,6,16 In all categories of cardiovascular disease, long-term survival was satisfactory in elective cases and poor in urgent/emergency cases. To improve the long-term outcome in dialyzed patients, an early operative indication should be considered to reduce the later need for an urgent or emergency operation. Two urgent/emergency operations for valve disease were due to infective endocarditis. Infective endocarditis is a known complication in hemodialysis patients, with an incidence of 0.0056% to 1.4%.17,18 The prognosis for hemodialysis patients with infective endocarditis is dismal; hospital mortality is 30%–60%, 1-year survival is 38.4%–56.3%, and 5-year survival is only 10.9%.17–19 A recent report noted perioperative mortality of 73% in hemodialysis patients undergoing valve replacement for infective endocarditis.20 In such patients, a strategy to prevent infective endocarditis is essential. Despite the poor outcome of urgent/emergency operations, results of elective operations in our dialyzed patients were satisfactory. Noninvasive examinations such as echocardiography, computed tomography, scintigraphy, and positron-emission tomography have enabled the detection of cardiovascular lesions in the early stages. It is well-known that many dialysis patients are complicated by cardiovascular disease, thus early diagnosis is essential.
There were several limitations in this study; as it was a retrospective and non-randomized study in a small number of patients with various cardiac diseases, we could not draw definitive conclusions. However, the superior midterm survival after elective surgery, comparable to the prognosis in dialyzed patients in general, supports our operative strategy. In addition, it indicates the importance of avoiding urgent or emergency surgery by regular examinations and early consultation for surgery in patients on dialysis who have cardiovascular disease.
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REFERENCES
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ABSTRACT
INTRODUCTION
