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Ann Thorac Surg 2000;69:464-474
© 2000 The Society of Thoracic Surgeons

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Original Articles

Risk factors and outcomes after coronary reoperation in 739 elderly patients

^a Departments of Thoracic and Cardiovascular Surgery, The Cleveland Clinic Foundation, Cleveland, Ohio, USA
^b Department of Biostatistics and Epidemiology, The Cleveland Clinic Foundation, Cleveland, Ohio, USA

Address reprint requests to Dr Lytle, Department of Thoracic and Cardiovascular Surgery, The Cleveland Clinic Foundation, 9500 Euclid Ave, F-25, Cleveland, OH 44195
e-mail: lytleb{at}ccf.org

	Abstract

Top Abstract Introduction Patients and methods Results In-hospital results Comment Appendix 1 Appendix 2 Appendix 3 References

 
Background. As second coronary artery bypass graft (CABG) operations are becoming more common in elderly patients, we conducted a retrospective analysis of risk factors for in-hospital and late outcome in patients aged 70 and over.

Methods. We reviewed records of 739 patients who underwent second CABG at age 70 or older at our institution between 1983 and 1993. Preoperative, operative, and postoperative variables were analyzed to identify predictors of in-hospital and long-term mortality.

Results. The mean age (± standard deviation) at reoperation was 74 ± 3 years and the mean interval after primary operation was 130 ± 55 months. In-hospital mortality was 7.6% (n = 56). Preoperative factors associated with increased in-hospital mortality were preoperative creatinine greater than 1.6 mg/dL (p < 0.001), emergency operation (p < 0.001), female sex (p = 0.012), moderate or severe left ventricular dysfunction (p = 0.049), and left main coronary disease (p = 0.045). In-hospital, actuarial survival was 75% at 5 years and 49% at 10 years. Cardiac event-free survival was 60% at 5 years and 27% at 10 years. The factors independently associated with increased late death were hematocrit (p = 0.046), diabetes (p = 0.011), peripheral vascular disease (p < 0.001), left ventricular function (p < 0.001), history of cancer (p = 0.016), preoperative nonsinus rhythm (p = 0.003), anticoagulation or antiplatelet therapy (p = 0.018), postoperative encephalopathy (p = 0.001), and postoperative stroke (p = 0.014).

Conclusions. CABG reoperation can have excellent results for many elderly patients, but mortality is markedly higher when elderly patients have certain risk factors and comorbidities, alone or in combination. This information should be helpful in educating patients before they decide whether to choose reoperation.

	Introduction

Top Abstract Introduction Patients and methods Results In-hospital results Comment Appendix 1 Appendix 2 Appendix 3 References

 
Increasingly elderly patients are being considered for coronary artery bypass graft (CABG) reoperation. Although long-term survival of patients after primary coronary revascularization is excellent, CABG is by no means curative. Thus, a large number of elderly patients will need coronary reoperation. In general, coronary reoperation is safe and effective. However, elderly patients have a higher incidence of preoperative comorbidities that may result in greater perioperative morbidity and increase the risk of early and late mortality.

No large study has been undertaken to examine the short-term and long-term outcomes of elderly patients undergoing a second CABG procedure. Thus, we analyzed the relationships between risk factors and both in-hospital and long-term outcome among patients who underwent a second isolated CABG procedure at age 70 or older.

	Patients and methods

Top Abstract Introduction Patients and methods Results In-hospital results Comment Appendix 1 Appendix 2 Appendix 3 References

 
With the aid of our institution’s cardiovascular information registry, we reviewed medical records and identified consecutive patients of at least 70 years of age who underwent a first isolated coronary reoperation at our institution between January 1983 and December 1993, regardless of the year of the first CABG. Patients who had undergone more than one previous cardiac operation or who had additional noncoronary operations as part of their first or second coronary operation were excluded.

Variables
The outcome and explanatory variables examined are listed in Appendices 1 through 3. In-hospital death was defined as death before hospital discharge, regardless of duration of the hospitalization. A patent artery was defined as any graft or native vessel that was not 100% occluded. Smoking between operations was included as a variable, but smoking before the first operation was not considered. Cardiac event-free survival after discharge was defined as survival without the following events: heart failure, arrhythmia requiring treatment, additional cardiac operation, interventional cardiac procedure, myocardial infarction, or angina recurrence of New York Heart Association (NYHA) functional class III or IV.

During the study period, oxygenated crystalloid or blood cardioplegia were used as myocardial protection at the discretion of the surgeon. Retrograde coronary sinus delivery of cardioplegic solution and delivery protocols varied according to surgeon and case.

Table 1 shows the preoperative patient characteristics. Table 2 shows number of grafts and the graft conduits at reoperation.

Statistical analysis
Data are summarized by frequencies and percentages (out of nonmissing data) for the categorical factors and means, standard deviations, medians, minimums, and maximums for the continuous factors. For in-hospital mortality, univariable analyses were performed by ² or Fisher exact tests for the categorical variables and Student’s t-tests or Wilcoxon’s two-sample tests for the continuous variables. Univariable Cox proportional hazard models or log-rank tests were used to access the individual relationship of each variable to late mortality and cardiac events. Kaplan-Meier estimates for the late results are reported in the text and parameter estimates, standard errors, hazard ratios, confidence intervals of the hazard ratios, confidence intervals of the hazard ratios and Wald ² p values based on the univariable Cox proportional hazard models are presented in the tables.

Risk factors at least marginally associated with an outcome on univariate analysis (p < 0.1) were used in the development of the univariable models. Stepwise regression methods were then used to determine the factors which were independently associated (p < 0.005) with the outcome. Based on the stepwise analyses, the results of the multivariable logistic regression model of in-hospital mortality and multivariable Cox proportional hazard models of late mortality and cardiac events are reported in the tables.

	Results

Top Abstract Introduction Patients and methods Results In-hospital results Comment Appendix 1 Appendix 2 Appendix 3 References

 
Seven hundred thirty-nine patients were included in the analysis. The mean age (± standard deviation [SD]) was 74 ± 3 years (range, 70 to 88 years). The mean interval (± SD) between surgeries was 130 ± 55 months (range, 0 to 300 months).

	In-hospital results

Top Abstract Introduction Patients and methods Results In-hospital results Comment Appendix 1 Appendix 2 Appendix 3 References

 
Mean total stay in the intensive care unit (ICU) was 4.7 ± 9.5 days (range, 0 to 112 days). Mean total length of postoperative hospital stay was 14.5 ± 14.8 days (range, 0 to 114 days). There were 56 (7.6%) in-hospital deaths. Cardiovascular causes accounted for 28 deaths, of which myocardial infarction was the cause in 14 patients (Table 3). Tables 4 and 5 show factors univariately associated with in-hospital mortality. Multivariable logistic regression analysis identified 5 preoperative factors independently associated with an increased risk of in-hospital mortality (Table 6). No patient had all 5 of these factors. Using this final model, we estimated the probability of in-hospital death and compared it with actual in-hospital mortality in our patients using combinations of these preoperative risk factors (Table 7). When all preoperative, intraoperative, and postoperative factors were considered, factors independently associated with an increased risk of in-hospital mortality are shown in Table 6. In-hospital morbidity is listed in Table 8.

View larger version (14K): [in this window] [in a new window]   Fig 1. Survival curves after coronary reoperation in the elderly. Actuarial survival was 75% at 5 years and 49% at 10 years. Actuarial survival without NYHA III or IV angina recurrence was 67% and 38% at 10 years. Actuarial cardiac event-free survival was 60% at 5 years and 27% at 10 years.

View larger version (9K): [in this window] [in a new window]   Fig 2. Cardiac event-free survival curve after coronary reoperation for elderly by preoperative creatinine level ( 1.6 mg/dL versus > 1.6 mg/dL). In the group with preoperative creatinine level equal or less than 1.6 mg/dL (solid line), cardiac event-free survival was 60% at 5 years and 27% at 10 years. In the group with preoperative creatinine level greater than 1.6 mg/dL (dashed line), it was 55% at 5 years and 14.8% at 9 years (last observation).

View larger version (9K): [in this window] [in a new window]   Fig 3. Cardiac event-free survival curve after coronary reoperation for elderly by preoperative history of diabetes mellitus. In the group without preoperative diabetic history (solid line), cardiac event-free survival was 65% at 5 years and 27% at 10 years. In the group with preoperative diabetic history (dashed line), it was 46% at 5 years and 26% at 10 years.

View larger version (9K): [in this window] [in a new window]   Fig 4. Cardiac event-free survival curve after coronary reoperation for elderly by preoperative history of peripheral vascular disease. In the group without preoperative history of peripheral vascular disease (solid line), cardiac event-free survival was 65% at 5 years and 32% at 10 years. In the group with preoperative history of peripheral vascular disease (dashed line), it was 52% at 5 years and 15% at 10 years.

View larger version (9K): [in this window] [in a new window]   Fig 5. Cardiac event-free survival curve after coronary reoperation for elderly by preoperative left ventricular function (normal/mild versus moderate/severe). In the group with normal left ventricular function or mild dysfunction, cardiac-event-free survival was 64% at 5 years and 27% at 10 years. In the group with moderate or severe dysfunction, it was 51% at 5 years and 25% at 10 years. (Solid line = normal/mild; dashed line = moderate/severe.)

	Comment

Top Abstract Introduction Patients and methods Results In-hospital results Comment Appendix 1 Appendix 2 Appendix 3 References

Despite the increased number of coronary reoperations for elderly patients, little is known about the in-hospital and long-term results for this group. Most studies have examined either coronary reoperation [3–5] in all patients or coronary bypass operation in the elderly [6–9]. The elderly patients who underwent coronary reoperation were analyzed in these studies as small subgroups.

According to previous studies, symptoms, hypertension, and left main coronary artery disease all tend to be more severe in elderly patients [7]. In our study, 68.7% were NYHA functional class III or IV, 48.4% were hypertensive, and -33.4% had left main coronary artery disease. In addition, 58.6% of patients had a myocardial infarction before coronary reoperation, and 36.2% had moderate or severe left ventricular dysfunction.

Our in-hospital mortality was 7.6%. Acinapura and associates reported an 8% in-hospital mortality after CABG reoperation in septuagenarians [6], a rate similar to the 8.9% mortality in patients aged 70 years or older reported by He and coworkers [10]. These studies focused on patient age (70 years or older), but patients who underwent reoperation were only a small proportion of the study group. Perrault and associates reported a 30-day mortality of 11% after coronary reoperation [4] in patients with a mean age of 58 years.

To identify elderly patients at high risk of in-hospital mortality after coronary reoperation preoperatively, we analyzed preoperative variables for in-hospital mortality separately. Multivariate analysis identified 5 preoperative factors for in-hospital mortality. When patients have none of these preoperative risk factors, the estimated probability of in-hospital death is only 2%. Thus, in elderly patients without these risk factors, CABG reoperation is as safe as primary CABG in younger patients. However, it is not uncommon for elderly patients to have comorbidities, including these preoperative risk factors. The estimated probability of in-hospital death of a patient with all risk factors is 86.1%.

Our mortality rate was skewed tremendously by these high-risk patients. The indication for coronary reoperation must be considered carefully for high-risk elderly patients. The goal of preoperative management is to optimize their renal function and left ventricular function and to avoid emergency reoperation. When this goal is achieved, the estimated probability of in-hospital mortality is greatly decreased. However, these conditions are often nonremediable, despite aggressive preoperative medical therapy. The presence of these conditions should prompt careful consideration of the risk-benefit ratio of operation, which should be discussed carefully with high-risk patients.

Mortality increases when coronary reoperation causes myocardial damage, which may present with the need for a postoperative intraaortic balloon pump and postoperative rhythm disturbance. Thus, meticulous dissection to avoid embolization caused by diseased grafts and thorough myocardial protection are important in decreasing in-hospital death [4, 11]. Rich and associates found that female sex was associated with increased mortality in younger patients but that this difference did not appear to extend to the elderly [12]. In contrast, our analysis indicated that female sex is a risk factor for increased in-hospital mortality. One reason for this high risk in women may be the smaller size of their coronary arteries, which makes CABG technically more difficult.

Incidence of perioperative myocardial infarction was 3.5%. This result is comparable with that of other studies [4, 6]. Our growing experience and the advent of retrograde cardioplegia has contributed markedly to this low rate for coronary reoperation. We obtain myocardial protection with an induction dose of antegrade cardioplegia, followed by liberal doses of retrograde cardioplegia although the details of delivery vary according to surgeon and case. Lytle and colleagues pointed out that the retrograde route not only allows delivery of cardioplegic solution but will also allow accumulated atherosclerotic debris to float out of coronary arteries [11]. The most common in-hospital cardiac morbidity was atrial fibrillation. The incidence of postoperative atrial fibrillation increases significantly with advancing age [7]. Postoperative atrial fibrillation is not regarded as a major complication. However, it greatly prolongs the hospital stay and therefore increases the cost of treatment. Recent data indicate that amiodarone is an effective preventive method for postoperative atrial fibrillation [13]. We do not have experience with prophylactic amiodarone.

Previous studies from our institution revealed that internal thoracic artery graft at the first coronary operation does not increase the risk at coronary reoperation [14, 15]. The present study confirmed that using the internal thoracic artery at the first operation does not increase the risk of in-hospital death at reoperation in elderly patients, so an internal thoracic artery graft should not be discouraged for elderly patients either at the first coronary operation or at reoperation.

Our findings show that symptomatic relief from angina after coronary reoperation is excellent. Before reoperation, 68.7% of our patients were NYHA functional class III or IV. A mean of 51 months after reoperation, 91.6% of patients were NYHA class I or II. Thus, coronary reoperation can provide elderly patients with a good quality of life.

For in-hospital survivors, actuarial survival was 75% at 5 years and 49% at 10 years. Actuarial survival without recurrence of NYHA III or IV angina was 67% at 5 years and 38% at 10 years, cardiac event-free survival was 60% at 5 years and 27% at 10 years.

Among long-term risk factors, a cancer history often rules out a patient being considered for coronary reoperation because late death from cancer is common in elderly patients. Patients with a previous history of any type of cancer must be evaluated carefully for local recurrence at the primary site and for any sign of metastasis. Patients with malignancies are usually not candidates for CABG unless they are severely limited by their ischemic heart disease and the malignant lesion is curable.

Mean total stay in the ICU was 4.7 days, and the mean total length of the postoperative hospital stay was 14.5 days. Length of ICU stay and total length of the postoperative hospital stay did not decline from 1983 to 1993. Both the ICU stay and postoperative stay are long, which inevitably increases the cost of coronary reoperation for the elderly. The costeffectiveness of coronary reoperation for elderly patients will be closely scrutinized.

In summary, elderly patients who require coronary reoperation tend to have more preoperative comorbidity and less physiological reserve than younger patients. They also tend to have more severe symptoms from ischemic heart disease. Coronary reoperation in the elderly is a significant surgical challenge. Overall, coronary reoperation can be performed with relatively low in-hospital mortality with excellent postoperative symptomatic relief and survival of 75% at 5 years and 49% at 10 years. However, for high-risk patients, the risk-benefit ratio of operation should be considered carefully. The findings of this study provide detailed information that should be discussed the patient and family members before deciding whether to choose repeat CABG.

	Appendix 1

Top Abstract Introduction Patients and methods Results In-hospital results Comment Appendix 1 Appendix 2 Appendix 3 References

 

	Appendix 2

Top Abstract Introduction Patients and methods Results In-hospital results Comment Appendix 1 Appendix 2 Appendix 3 References

	Appendix 3

Top Abstract Introduction Patients and methods Results In-hospital results Comment Appendix 1 Appendix 2 Appendix 3 References

	References

Top Abstract Introduction Patients and methods Results In-hospital results Comment Appendix 1 Appendix 2 Appendix 3 References

1. Bureau of the Census. Statistical abstract of the United States, 1996. 116th ed. Washington DC: Government Printing Office, 1996.
2. Cosgrove D.M., Loop F.D., Lytle B.W., et al. An 11-year evolution of coronary arterial surgery (1967–1978). Ann Surg 1979;190:444-455.[Medline]
3. Loop F.D., Lytle B.W., Cosgrove D.M., et al. Reoperation for coronary atherosclerosis. Changing practice in 2509 consecutive patients. Ann Surg 1990;212:378-386.[Medline]
4. Perrault L., Carrier M., Cartier R., et al. Morbidity and mortality of reoperation for coronary artery bypass grafting. Cardiovasc Surg 1991;7:427-430.
5. Salomon N.W., Page U.S., Bigelow J.C., Krause A.H., Okies J.E., Metzdorff M.T. Reoperative coronary surgery. J Thorac Cardiovasc Surg 1990;100:250-260.[Abstract]
6. Acinapura A.J., Rose D.M., Cunningham J.N., Jr, Jacobowitz I.J., Kramer M.D., Zisbrod Z. Coronary artery bypass in septuagenarians. Circulation 1988;78(Suppl I):179-184.
7. Loop F.D., Lytle B.W., Cosgrove D.M., et al. Coronary artery bypass graft surgery in the elderly. Cleve Clin J Med 1988;55:23-34.[Medline]
8. Mullany C.J., Darling G.E., Pluth J.R., et al. Early and late results after isolated coronary artery bypass surgery in 159 patients aged over 80 years and older. Circulation 1990;82(Suppl IV):229-236.
9. Salomon N.W., Page U.S., Bigelow J.C., et al. Coronary artery bypass grafting in elderly patients. Comparative results in a consecutive series of 469 patients older than 75 years. J Thorac Cardiovasc Surg 1991;101:209-218.[Abstract]
10. He G.W., Acuff T.E., Ryan W.H., Bowman R.T., Douthit M.B., Mack M.J. Determinants of operative mortality in elderly patients undergoing coronary artery bypass grafting. J Thorac Cardiovasc Surg 1994;108:73-81.[Abstract/Free Full Text]
11. Lytle B.W. Coronary reoperations. Coron Artery Dis 1993;4:703-706.[Medline]
12. Rich M.W., Keller A.J., Schechtman K.B., Marshall W.G., Jr, Kouchoukos N.T. Morbidity and mortality of coronary bypass surgery in patients 75 years of age or older. Ann Thorac Surg 1988;46:638-644.[Abstract]
13. Daoud E.G., Strckberger S.A., Man K.C., et al. Preoperative amiodarone as prophylaxis against atrial fibrillation after heart surgery. NEJM 1997;337:1785-1791.[Abstract/Free Full Text]
14. Lytle B.W., McElroy D.M., McCarthy P.M., et al. Influence of arterial coronary bypass grafts on the mortality in coronary reoperations. J Thorac Cardiovasc Surg 1994;107:675-683.[Abstract/Free Full Text]
15. Bailot R.G., Loop F.D., Cosgrove D.M., Lytle B.W. Reoperation after previous grafting with the internal mammary artery. Ann Thorac Surg 1985;40:271-273.[Abstract]

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