Eur J Cardiothorac Surg 2004;25:59-64
© 2004 Elsevier Science NL
Long-term cardiac survival after reoperative coronary artery bypass grafting
Luc Noyeza*,
Frans M. van Eckb
a Department of Thoracic and Cardiac Surgery, 414, PO Box 9101, 6500 HB Nijmegen, The Netherlands
b Heart Center, University Medical Center, St. Radboud, Nijmegen, The Netherlands
Received 14 July 2003;
received in revised form 21 September 2003;
accepted 4 October 2003.
* Corresponding author. Tel.: +31-24-3613711; fax: +31-24-3540129
e-mail: l.noyez{at}thorax.umcn.nl
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Abstract
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Objective: Despite advances in cardiac surgery, the risk of reoperative coronary artery bypass surgery (RECABG) still exceeds those of a primary myocardial revascularization and also the late results are not so favourable. In this study, long-term cardiac survival is analyzed. Methods: We analyzed long-term cardiac survival of 466 patients who survived the first 6 months after a RECABG between January 1987 and December 1998. Actuarial survival estimates were calculated and pre- and peroperative variables were analyzed to identify predictors of long-term cardiac related mortality. Results: Mean follow-up was 7.7±3.8 years (1–17 years), and follow-up was 95.6% complete. One-year cardiac survival was 98.2%, 5-year: 91.0%, 10-year: 78.7% and 14-year survival 60.2%. Cardiac survival was only significantly superior for patients under 65 years of age at the moment of the RECABG. Impaired left ventricular function was identified as the only independent predictor of late cardiac-related mortality. Conclusion: The long-term survival in patients undergoing RECABG is acceptable. Once patients survived the first 6 postoperative months, advanced age (>65 years) is affecting long-term cardiac survival and impaired left ventricular function is the only independent predictor of late cardiac mortality.
Key Words: Coronary • Reoperation • Cardiac survival
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1. Introduction
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Patients undergoing reoperative coronary artery bypass surgery (RECABG) have higher mortality, perioperative as well as at long-term, compared with patients undergoing a primary myocardrevascularization (CABG) [1–4]. Since the study of Blackstone, using hazard function methology for time-related events, it is clear that risk factors must be identified for each phase of hazard [5]. In previous articles we focussed on mortality in the early 6-month phase after RECABG [6,7]. The present study concerns the long-term survival of patients surviving the early postoperative phase after RECABG. This is in contrast with most other studies evaluating long-term results starting their ‘long-term analysis’ at the moment of the operation or hospital discharge.
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2. Material and methods
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2.1. Patients
With the aid of our database, Coronary Surgery Database Radboud Hospital (CORRAD), a registry that stores pre-, peri-, postoperative and follow-up data on all patients undergoing isolated coronary bypass grafting, we identified a series of 541 patients undergoing a first RECABG from January 1987 to December 1998 at the UMC St. Radboud Nijmegen.
The clinical indication for RECABG was angina and proven ischemia despite medical therapy with ß blockers, calcium antagonists or nitrates, or a combination. We distinguish between three groups: (1) elective operations, patients with stable cardiac function usually scheduled at least 1 day prior to the surgical procedure; (2) urgent operations, when surgery is required within 24 h after admission; and (3) emergency operations, in case of operation for evolving infarction, ischemia not responding to medical therapy, or cardiogenic shock. Probably due our restrictive attitude for PTCA of diseased vein grafts, only two patients were operated in emergency after a failed PTCA. Forty-one patients (7.5%) were reoperated for early graft failure, 130 patients (24.1%) for late graft failure, 49 patients (9.1) for progression of athersosclerosis in the native coronary system, 314 patients (58.1%) for a combination of late graft failure and progression of athersosclerosis in the native coronary system, and seven patients (1.2%) for incomplete revascularization. The mean interval between the CABG and RECABG was 141±59 months (0–300).
Hospital mortality 36/541 (6.7%) and early phase—6-month—mortality 75/541 patients (13.9%) were the subject of our previous studies [6,7]. The 466 surviving patients were entered in this follow-up study. The studied pre- and peri-operative variables are listed in Table 1.
To be able to compare our survival rates with other studies, we also calculated survival for the total patient population (541 patients) starting from the operation.
2.2. Follow-up
Follow-up information is based on data from cardiologists, family doctors, and an annual survey sent directly to the patients. A cross-sectional follow-up was performed in December 2002. If there was no response from the patient, the information was traced by telephone contact with the patient, family, doctor, or government records. In case of death, the cardiologist, family doctor, or patients family was contacted to identify the cause of death.
2.3. Statistical analysis
Actuarial survival estimates were calculated using the Kaplan–Meier method and compared using the log-rank test. Univariate analysis and multiple logistic regression analysis were used to identify risk factors that independently predicted long-term cardiac-related mortality. A P-value of 0.05 or less was considered significant.
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3. Results
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Four hundred and sixty-six patients with a mean age of 63.4±8.4 years (median 64, range 32–91) were included in the follow-up. Follow-up was 95.6% complete, 20 patients were lost for follow-up. Mean follow-up was 7.7±3.8 years, median 7.0 years and a range of 1–17 years. There were 138 late deaths: in 89 patients there was a proven cardiac related death, in four patients the cause of death was unknown, however, these deaths were computed as cardiac deaths. Thus, we have 93 patients (67.4%) with a cardiac related death. In the other 45 patients (22.6%) death was of non-cardiac cause, 21 of them died of cancer.
The total 1-year survival is 97.3%, 5-year: 86.8%, 10-year: 68.6% and a 14-year survival of 48.1%. The cardiac survival is presented in Fig. 1
. The 1-year cardiac survival is 98.2%, 5-year: 91.0%, 10-year: 78.7% and a 14-year survival of 60.2%. Cardiac survival was only significantly superior for patients under 65 years of age compared to older patients (P=0.002) (Fig. 2) for the other studied variables (Table 2) there was no significant difference in survival.
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Fig. 1. Cardiac survival for survivors of the early postoperative phase after reoperative coronary bypass surgery.
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Fig. 2. Cardiac survival divided by age (P=0.002, log rank test) Dotted line patients younger than 65 years. Full line patients aged 65 years or older.
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Table 2. Studied variables tested for their association with long-term cardiac survival and P-value (log-rank test)
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To be able to compare our survival rates with other studies, we also calculated survival for the total patients population (541 patients) starting from the operation. This resulted in a 1-year survival of 83.8%, 5-year: 76.9% and a 10-year survival of 60.6%. Cardiac survival was 84.8%, 78.5%, and 66.5%, respectively.
Univariate analysis identified impaired left ventricular function (P=0.02) and mild valve disease (P=0.04) as two variables related with late cardiac mortality (Table 3). Impaired left ventricular function is identified by multivariate analysis (Table 4) as the only independent variable for late cardiac mortality (P=0.021).
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4. Discussion
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Based on the work of Blackstone, using hazard function methodology for the occurrence of a time related event, as postoperative death, a three-phase hazard function was identified. An early phase, during the first postoperative months, prolonged in high risk patients and influenced by patient and procedural related variables, a constant and a late phase [5,8]. In our previous work we analyzed the occurrence of mortality during the early phase after RECABG [6,7]. In the present study we analyzed long-term survival of patients undergoing a RECABG because each phase has its own risk factors. We started our survival analysis at the end of the early phase, 6 months postoperative. This is different from other survival studies, and consequently it is difficult to compare our results with these studies [9–17]. Therefore, we also calculated survival for our entire patient population.
Table 5 gives a review of different survival studies. Studied period, number of patients, age, mortality, patients included in follow-up, and 5 and 10-year survival are summarized. Because some studies give reviews over different periods, the indicated age is only approximate [11,12]. It must be clear, however, that several points make the comparison difficult. First, the studied patients population are operated in different time frames. This is not only important because of different surgical techniques, patient profile, but also because the indication for RECABG changed over the years [11,12,18–22]. In the early 1970s, the majority of RECABG's were performed because of progression of atherosclerosis in the native coronary system or due to incomplete revascularization. Later in the 1980s, the reason for RECABG had shifted to predominantly failure of the graft. In recent years, more and more patients are reoperated because of progression of the disease in the native system, in combination with patent arterial grafts [22]. Second, the age of the studied populations is different, varying between 56 and 80 years, or even older [16]. Age is indicated in several studies as an important variable influencing survival [1,10–12,14,17]. Third, in several studies the hospital period, mortality, is included or not included in the survival analysis. Fourth, it is difficult to compare the risk of the studied patient populations. Risk analysis models, such as Parsonnet [23], or Euroscore were not used [24] and the reported operative, hospital or 30-day mortality, probably an indication of the risk of the operated population, varies in all these studies.
The two studies most comparable with ours are from Weintraub et al. [14], especially in the section separately evaluating a group of patients aged between 60 and 69 years, operated between 1975 and 1993 (indicated as Weintraub [II] in Table 5). The difference is that this study began in 1975; of the 2030 described patients 471 patients were operated before 1985, but hospital mortality and long-term survival are comparable with our results for the entire group. The second study is from Shapira [17], the reported 30-day mortality (3%) and long-term survival (90%, 74%) seems superior to our results. The number of patients and mean age of the studied population are comparable, however, the study starts in 1978 and ends in 1989. Looking to the indications for reoperation, this study shows a high percentage of incomplete revascularization (11.1%), a low percentage of combined graft failure and progression of the disease (22.5%). If we compare this with our previous study and other studies, it is clear that this patient population is not comparable with our described population or other recent studies of patients undergoing RECABG [10,13–16,22].
Starting our survival analysis at 6 months postoperatively, cardiac related survival only seems to be influenced by age (older or younger than 65 years). Age is identified in several other survival studies [1,10–12,14,17], however, in contrast to a majority of these studies, co-morbidity factors and cardiac related variables are not identified as variables with a significant adverse effect on cardiac related longevity. However, diabetes (P=0.06), female gender (P=0.07), and impaired left ventricular function (P=0.07), bend to significance in our analysis. After uni- and multivariate analysis impaired left ventricular function is identified as the only independent predictor of late cardiac related mortality after redo surgery. Impaired left ventricular function is identified by several other studies as a predictor for cardiac related mortality, however, other variables such as diabetes, hypertension, emergency surgery and others identified in these reports were not significant in our analysis [1,2,10–17].
One criticism is that some variables are not included in our analysis. The most important is certainly completeness of the revascularization at the moment of the RECABG. In four patients (0.8%) it was preoperatively decided to do an incomplete revascularization (two patients with a single graft to the LAD and one patient with a single graft to the right coronary artery, and this despite pathology in the circumflex arteries, in another patient with extensive pathology, only an additional IMA graft was constructed to a diseased vein graft to the LAD). All the other RECABG's were performed with a complete revascularization as starting point. However, diffuse pathology, lack of graft material, make the definition of completeness of revascularization in RECABG extremely difficult. The question is; is revascularization complete if the surgeon performed all preoperatively planed grafts and distal anastomoses, or if the surgeon performed as much as possible of the preoperatively planned grafts and distal anastomoses, without increasing the risk for complications during the operation. It was even surprising that in our review of the literature [1,11–17], only in the study of BW Lytle et al. is completeness of revascularization analyzed [11]. Completeness of revascularization is, however, not clearly defined and the study describes patients undergoing a RECABG between 1967 and 1984. As already mentioned in this discussion, it is difficult to compare these patients with our patients. Most of these patients had not even a complete revascularization at the CABG, and even during the RECABG completeness of revascularization varies between 51% and 75%. It is remarkable that the following study of the Cleveland Clinic [12], completeness of revascularization, is not analyzed. The changing profile of patients undergoing a RECABG, an increase of patients with progression of atherosclerosis in the native coronary arteries and patent arterial grafts [22], only complicates the definition of complete revascularization. A patient with a patent IMA graft to the LAD, reoperated with new grafts to the distal right coronary artery and to the circumflex. But without a graft to a calcified diagonal branch, because of the risk of peroperative problems. Is this a complete revascularization or not? On the other hand, we realize that in these patients it would be interesting to know if completeness of revascularization is important. A recent study of Czerny et al. showed indirectly that completeness of the revascularization affects significant recurrence of angina but could not show a difference in long-term survival (mean follow-up 50±23 months) [25].
Another point of criticism is that secondary prevention and certainly medical therapy changed over the years. At our department, patients reoperated before 1992 received mostly no platelet-inhibiting agents after the CABG. Systematic control of cholesterol or lipoprotein status, use of statins, are important but changed over the years. However, this information is not registered in our database and thus not available.
In spite of the limitations of our study, the importance is that once patients survive the early postoperative period (6 months) after RECABG, their cardiac related survival is influenced by age, and that an impaired left ventricular function is the only independent predictor for cardiac related mortality. These findings confirm the importance of the early postoperative period and the identified variables, it seems that the early postoperative period is an executioner, selecting the strongest patients.
In conclusion, the long-term survival in patients undergoing reoperative coronary artery surgery are acceptable. Once patients survived the first 6 postoperative months, only advanced age (>65 years) is affecting long-term cardiac survival and impaired left ventricular function is the only independent predictor of late cardiac mortality.
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Abstract
1. Introduction
