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Ann Thorac Surg 1996;61:1746-1751
© 1996 The Society of Thoracic Surgeons
Department of Surgery, University of Hong Kong, The Grantham Hospital, Hong Kong, The Albert Starr Academic Center for Cardiac Surgery, Providence, and St. Vincent Hospital & Medical Center, Portland, Oregon
Accepted for publication February 7, 1996.
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Abstract |
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Methods. From November 1964 to July 1994, 963 elderly patients underwent isolated AVR. Long-term survival was investigated in 877 patients (70 to 94 years) who survived operation, with 92% follow-up completeness (mean ± standard deviation, 4.5 ± 3.9 years; maximum, 20.1 years; total, 3,920.2 patient-years), by univariate and multivariate analyses.
Results. Actuarial survival was 38.1% ± 2.8% at 10 years, 17.8% ± 3.0% at 15 years, and 9.0% ± 3.1% at 20 years. Eight variables (age, sex, body surface area [less or greater than 1.7 m2], period of operation, type of prosthesis, size of prosthesis, re-replacement, and concomitant coronary artery bypass grafting) were investigated with regard to long-term survival by the Kaplan-Meier method. Age, sex, and body surface area were significant. Multivariate analysis revealed that older age (p = 0.0005) and male sex (p = 0.0001) were independent variables that determined long-term survival.
Conclusions. Elderly patients may have satisfactory long-term results after AVR. Age and sex are independent determinants. Other factors (such as concomitant coronary artery bypass grafting and type of prosthesis) did not independently influence long-term survival. Coronary revascularization in elderly patients with coronary disease undergoing AVR may lead to a long-term survival similar to that in patients without coronary disease undergoing AVR.
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Introduction |
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70 years) with aortic valve disease [1–9]. It has been demonstrated that isolated AVR can be performed with a low operative mortality rate in elderly patients [2, 3, 10], but the performance of concomitant surgical procedures may expose these patients to higher operative risks [4]. Although the determinants for long-term survival after AVR have been studied, such determinants in elderly patients are not well established. A considerable percentage of elderly patients also have coronary artery disease and need coronary artery bypass grafting (CABG) during AVR. Although there are some studies on the influence of concomitant CABG on long-term survival in AVR patients [2, 4, 11, 12], such an influence has not been clear in the elderly. Lately, CABG has been performed in the elderly with increasing frequency because of the increasing number of elderly patients in the general population, the improving safety of CABG, the increasing incidence of coronary artery disease, and the higher mortality rate after acute myocardial infarction [13, 14], the incidence of which may be reduced by CABG.
The present study was designed to investigate the determinants of long-term survival in the elderly (70 years old) after AVR, with emphasis on the influence of concomitant coronary grafting on survival.
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Material and Methods |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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illustrates the distribution of patient age. Twenty-eight patients (3.2%) had previous AVR. Prostheses used included mechanical valves (early Starr-Edwards in 61 [7%], current Starr-Edwards [model 1260 since 1969] in 276 [31.5%], Björk-Shiley in 13 [1.5%], St. Jude in 38 [4.3%] and tissue valves (Carpentier-Edwards porcine in 365 [41.6%] and Carpentier-Edwards pericardial in 118 [13.5%]) (Table 1).
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Chart review was also carried out when necessary. Operative death was defined as any in-hospital death or out-of-hospital death occurring within 30 days after operation.
Operative Technique
An AVR was performed under the usual methods of cardiopulmonary bypass. After 1980, strategies for myocardial protection during operation included cardioplegia and moderate hypothermia. Core temperature was lowered to 25° to 30°C. After 1990, retrograde cardioplegia introduced through a coronary sinus cannula was used in some patients. The heart was maintained at approximately 20°C or less using intermittent cardioplegia every 20 to 30 minutes. After the aortic valvular leaflets were excised, the prosthetic valve was implanted with interrupted sutures. Selection of the valve prosthesis was based on the patient's age and the surgeon's preference.
Data Collection
A prospective data collection system and follow-up service has been in place since 1960. Initial information comes from review of hospital records, performed originally by chart extraction and more recently using point-of-care computerized data bases. The follow-up system is staffed by full-time clinical specialists who attempt to contact each patient at least annually, on the anniversary of their operation. The questionnaire consists of several questions to elicit functional class, medications, any heart-related clinical events since their last follow-up contact, and, recently, quality of life. Unsuccessful follow-up attempts are followed by repeated efforts, by mail or telephone, to the patient, an alternate contact, and the physician offices.
Statistical Methods
In this study, our primary concern was long-term survival and freedom from complications. We therefore based the analyses primarily on operative survivors (n = 877).
Univariate analysis used nonparametric actuarial survival [15] for estimating actuarial event-free rates and the log-rank statistic for comparisons [16]. Eleven variables (age, sex, preoperative functional class, body surface area [BSA], small BSA [<1.7 m2], period of operation, previous AVR, type of prosthesis, size of prosthesis, concomitant CABG, and re-replacement) were investigated with regard to long-term survival by the Kaplan-Meier method. Complication-free survival was also established. This survival curve excluded the patients who had bleeding due to anticoagulant therapy, thromboembolism, re-replacement, or subacute bacterial endocarditis.
To determine the simultaneous effects of multiple risk factors, we used semiparametric multivariable proportional hazard regression [17]. Risk factors that were significant or nearly so (p < 0.2) by univariate analysis were entered into a forward stepwise regression; entry to the model was based on the likelihood ratio statistic based on the maximum partial likelihood estimates (SPSS, Inc, Chicago, IL). A p value less than 0.05 was considered significant.
Coronary artery disease was classified as single-, double-, or triple-vessel disease based on a 70% or greater narrowing of luminal diameter of the left anterior, circumflex, or right coronary artery. Left main disease was defined as 50% or greater narrowing.
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Results |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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gives the long-term survival and complication-free survival.
Univariate Analysis
Eight variables (age, sex, BSA less or greater than 1.7 m2, period of operation, type of prosthesis, size of prosthesis, re-replacement, and concomitant CABG) were investigated with regard to long-term survival by the Kaplan-Meier method. Age, sex, and BSA were significant.
Influence of Age on Long-Term Survival
The influence of older age was reflected by decreased survival. In patients younger than 75 years, the survival was 41.9% ± 3.8% at 10 years (n = 50) and 24.6% ± 4.1% at 15 years (n = 15). In contrast, in patients older than 75 years, the survival was 33.8% ± 4.0% at 10 years (n = 28) and 5.4% ± 3.4% at 15 years (n = 2) (p = 0.02) (Fig 2). (Note that the Kaplan-Meier curves for each subgroup terminate at the time of the last death [or event] in that subgroup, and patients surviving beyond that time are not indicated. But in fact, such patients could be shown by extending the last point on the curve horizontally to the duration of the longest survivor in the subgroup.)
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. Female patients had better long-term survival. In the female patients, the survival was 81.4% ± 2.5% at 5 years (n = 139), 49.1% ± 4.8% at 10 years (n = 34), and 26.0% ± 5.7% at 15 years (n = 9). In contrast, in the male patients, the survival was 68.9% ± 2.4% at 5 years (n = 192), 31.7% ± 3.3% at 10 years (n = 44), and 13.6% ± 3.3% at 15 years (n = 9) (p = 0.0001) (see Fig 3).
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1.7 m2) on long-term survival was examined. A BSA less than 1.7 m2 was a significant variable in the patients whose BSA was recorded (n = 574). The patients who had a small BSA (<1.7 m2) had better long-term survival: 81.3% ± 3.5% at 5 years (n = 67), 40.0% ± 8.5% at 10 years (n = 7), and 16.0% ± 9.4% at 15 years (n = 2). In contrast, in the patients whose BSA was greater than 1.7 m2, the survival was 70.0% ± 2.9% at 5 years (n = 113), 37.5% ± 6.2% at 10 years (n = 8), and 31.2% ± 7.7% at 15 years (n = 5) (p = 0.023) (Fig 4).
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). The survival was 82.7% ± 3.2% at 5 years (n = 89), 45.8% ± 6.3% at 10 years (n = 19), and 30.3% ± 7.8% at 15 years (n = 4). In contrast, in the patients who received larger prostheses (>21 mm), the survival was 71.3% ± 2.1% at 5 years (n = 241), 35.9% ± 3.1% at 10 years (n = 61), and 15.0% ± 3.1% at 15 years (n = 13) (p = 0.008) (see Fig 5).
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). Patients who had AVR without concomitant CABG had slightly better long-term survival than those with concomitant CABG: 76.1% ± 2.3% at 5 years (n = 197), 40.0% ± 3.7% at 10 years (n = 45), and 20.2% ± 4.4% (n = 10) at 15 years versus 70.7% ± 2.8% at 5 years (n = 133), 35.6% ± 4.2% at 10 years (n = 32), and 14.5% ± 3.9% at 15 years (n = 10).
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Freedom From Thromboembolism and Bleeding Complications
The freedom from thromboembolism was 88.4% ± 2.0% at 5 years (n = 317) and 74.2% ± 3.7% at 10 years (n = 73). With regard to thromboembolic complications, there was no difference between tissue valves (85.6% ± 2.1% at 5 years [n = 172] and 74.0% ± 3.5% at 10 years [n = 58]) and mechanical valves (86.7% ± 2.1% at 5 years [n = 149] and 75.0% ± 4.3% at 10 years [n = 32]) (p = 0.6). Similarly, there were no differences between male and female patients (p = 0.9) or between patients who were younger than 75 and those who were older than 75 years (p = 0.2).
The freedom from bleeding complications was 93.0% ± 1.1% at 5 years (n = 341), 87.1% ± 2.2% at 10 years (n = 74), and 77.1% ± 6.6% at 15 years (n = 13).
Incidence of Re-Replacement
The freedom from re-replacement in the survivors was 97.9% ± 0.9% at 5 years and 96.42% ± 1.4% at 10 years. There was no difference between male and female patients with regard to the incidence of re-replacement of the aortic valve (p = 0.6). There was also no difference between patients who were younger than 75 and those who were older than 75 (p = 0.1).
Multivariate Analysis (Cox Proportional Hazard Regression)
Two regression analyses were performed. Because BSA was recorded in 574 patients and it was a significant variable in the univariate analysis, one of the regressions included BSA and the other one did not.
Nine variables were included in the first Cox hazard regression: age as a continuous variable, age 75 years or less versus greater than 75 years, gender, BSA as a continuous variable, BSA less than 1.7 m2, the type of valve prosthesis, concomitant CABG, the size of the prosthesis as a continuous variable, and small size of the prosthesis (
21 mm versus >21 mm). This regression analysis revealed that age, concomitant CABG, and gender were independent variables for determining long-term survival after AVR in patients over 70 years old (Table 2).
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Comment |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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Although AVR has been an acceptable operative treatment for elderly patients suffering from aortic valve disease, the long-term survival after AVR has not been well established, even though this is important information to estimate the effect of AVR in this age group. On the one hand, aortic valve disease, particularly the degenerative lesion, is one of the most common diseases in the elderly; on the other hand, there is little information with regard to late survival, which is the main index of the success of such an operation in this particular age group. Therefore, studies on the late results after AVR in the elderly are important in many respects.
Risk Factors for Long-Term Survival
The influence of older age on the operative mortality rate was obvious in previous studies [18]. The present study confirmed the influence of old age on long-term survival. Our study showed that in patients between 70 and 75 years old, the 10-year survival was still 41.9% ± 3.8%. However, it decreased with further aging. This shorter life expectancy for patients older than 75 years should be taken into account when the decision for operation is being made.
The influence of sex on long-term survival in elderly patients was also significant. In our study, the higher 10- to 15-year survival in women (49.1% ± 4.8% versus 31.7% ± 3.3% at 10 years and 26.0% ± 5.7% versus 13.6% ± 3.3% at 15 years) (see Fig 3) clearly demonstrated this difference. This implies that long-term survival for older women after AVR may be better than that for male patients.
One of the primary goals of the present study was to investigate whether concomitant CABG is a risk factor for late survival in elderly patients undergoing AVR. Theoretically, the influence of concomitant CABG should be viewed in two aspects. First, those patients who had concomitant CABG had coronary artery disease that increased their risk even after concomitant CABG, compared with the patients who had only aortic valve lesions without coronary artery disease. Second, such concomitant CABG may reduce the risk compared with the patients who had mild coronary artery disease that may not need CABG during the AVR, but may be progressive later. Therefore, the influence of concomitant CABG on late survival may be complex. In addition, the patients with coronary artery disease have less severe aortic valve disease on average; in other words, their operative indication is coronary artery disease and their aortic valve disease is not as severe as that in the patients who have aortic valve disease alone. This factor may also contribute to the findings in the present study that concomitant CABG was not an independent risk factor, as demonstrated by the second regression, which included all 877 patients.
We have demonstrated recently that in patients with a small aortic root, small BSA favors the long-term results. Because of such an influence and because a considerable number of elderly patients have a small aortic root [10], in the present study we also looked at the influence of small BSA on late survival (p = 0.023; see Fig 4). We included this variable in the equation because of its importance, although over a 20-year period it was recorded in only 65.5% of the patients. The regression showed that BSA is not an independent factor for survival.
Type and Size of Prosthesis
With regard to the type of valve prosthesis used, there have been a number of studies that reported satisfactory long-term results after AVR in elderly patients using either mechanical [3, 4, 19] or bioprosthetic [9, 20] valves. The present study did not detect any difference between mechanical and bioprosthetic valves.
With regard to the size of the prosthesis, we demonstrated in a previous study [10] that there was no difference in long-term survival between patients who received a small (21 mm) or a larger (>21 mm) prosthesis. However, our present study showed that, by univariate analysis, long-term survival in elderly patients after AVR was better in those who received smaller prostheses (21 mm) (p = 0.009). This probably occurred because more female patients received small prostheses. As demonstrated earlier, the present study showed that women had better long-term survival after AVR. Nevertheless, the multivariate analysis ruled out the size of the prosthesis as an independent risk factor for long-term survival.
Incidence of Thromboembolic and Re-Replacement Complications
In this experience, the incidence of complications was low, as seen from the complication-free survival rate (see Fig 1B). Thromboembolism and re-replacement were studied by two major determinants of long-term survival (ie, age and sex) and by the type of prosthesis (mechanical or tissue valve). There was no difference between these subgroups. Similar results were seen for re-replacement. Therefore, the major determinants of long-term survival after AVR in the elderly do not relate directly to the incidence of major complications.
In conclusion, elderly patients may have satisfactory long-term results after AVR, for which age and sex are independent determinants. Other factors (such as concomitant CABG and type of prosthesis) did not independently influence long-term survival. Coronary revascularization in elderly patients with coronary disease undergoing AVR may lead to a long-term survival similar to that in patients without coronary disease undergoing AVR.
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Acknowledgments |
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TopFootnotesAbstractIntroductionMaterial and MethodsResultsCommentAcknowledgmentsReferences |
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