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Ann Thorac Surg 1995;59:112-117
© 1995 The Society of Thoracic Surgeons

Health Status After Myocardial Revascularization: Inferior Results in Women

Department of Surgery, Torrance Memorial Medical Center, Torrance, California

Accepted for publication July 12, 1994.

	Abstract

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
We followed up 1,335 patients (287 female, 1,048 male) for 2 to 18 years (mean, 4.3 years) after they had undergone coronary artery bypass grafting. A health status index was calculated on the basis of their responses to annual questionnaires. The female patients were older (64.1 ± 0.3 versus 60.4 ± 0.3 years) and had a higher incidence of diabetes (28.6% versus 16.1%). The risk profile of women was otherwise similar to that of men. The hospital mortality was significantly higher in the women, particularly in those younger than age 60. The probability of survival (Kaplan-Meier) at 5, 10, and 15 years was lower in female patients at each interval. The mean health status index was also lower in women at 5, 10, and 15 years, and also lower in all subsets. In nondiabetic patients, the hospital mortality and probability of survival at 10 years did not differ between the female and male patients. In the diabetic patients, the hospital mortality was 11.0% (women) and 3.6% (men); the survival at 10 years was 0.42 (women) and 0.56 (men) (p < 0.001). Thus, the health status in women is less satisfactory than that of men after myocardial revascularization, and the probability of survival is lower. The excess mortality in female patients may be due to the higher incidence of diabetes in this group.

	Introduction

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
Coronary atherosclerosis that affects women differs from the disease that affects men. The disease is first manifested at a later age, and the presenting event is more likely to be angina rather than death or myocardial infarction [1]. The morbidity associated with myocardial infarction is greater in women, and the potential for rehabilitation less [2]. Although the relative risk of coronary artery disease in persons less than 65 years of age is twice as great for men, the risk for women older than this is approximately the same as that in the older men.

Not surprisingly, the risk associated with coronary artery bypass procedures is greater in women [3, 4]. This has been attributed to anatomic differences, such as small vessel size and lower graft patency [5], and to referral bias, in that higher-risk female patients may be referred for surgical intervention [6].

Quality-of-life variables have been infrequently studied in patients who have undergone coronary artery bypass procedures, and the impact of gender has not been evaluated. To gain further insight into this situation, we prospectively followed up on a large series of patients upon whom myocardial revascularization was performed using a method for evaluating quality of life initially suggested by Weinstein and Stason [7]. These authors recommended the periodic calculation of a health status index in which the definable health status, ranging from death to varying degrees of disability to full health, is assigned a weight of from zero to one. Health outcomes that are expressed in terms of quality of life are necessarily subjective. We therefore mailed questionnaires to the patients annually in which they were asked to evaluate their health status in comparison with their status before operation.

In a previous study on the effect of increasing age in patients who undergo myocardial revascularization, we found that the quality of life after revascularization was better, the improvement lasted longer, and the risk of reoperation was less in older patients [8]. In the present study, we analyzed the effect of gender on survival and health status after coronary artery bypass grafting.

	Material and Methods

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
This series included all patients upon whom myocardial revascularization procedures were performed by the two senior authors (J.S.C. and R.A.C.) from January 1972 through December 1988 at several private hospitals in Los Angeles. Those patients who were operated on at Wadsworth Veterans' Administration Hospital in Los Angeles, which were included in a previous study [8], were not included in this analysis to eliminate the gender bias that would be produced by their inclusion. Patients having concomitant valve replacement were also excluded.

Saphenous vein grafts were used in all patients, with internal mammary artery grafts used selectively until after 1982, when the internal mammary artery graft began to be used preferentially for the left anterior descending coronary artery. Bilateral internal mammary artery grafts were used only when vein graft material was inadequate and occasionally in younger patients.

Questionnaires were sent to patients at 6 and 12 months after operation and annually thereafter. In it were questions about the presence or absence of symptoms and whether the patients had had any interventional procedures during the follow-up interval. The patients were asked to evaluate their health status in comparison with their status before the operation and to rate it as ``greatly improved,'' ``slightly improved,'' or ``not improved or worse.'' The health status index was recorded as follows: asymptomatic, greatly improved, 1.0; mild symptoms, greatly improved, 0.8; moderate symptoms, slightly improved, 0.6; and not improved or worse, 0.4. The return rate of the questionnaires was excellent, but occasionally it was necessary to contact patients by telephone or through relatives. The primary source of the health status information was, however, the questionnaires, and these provided an objective measure of the patients' subjective impression of their response to the operation. The data were coded primarily by two persons: a retired medical records librarian and one of us (L.K.M.S.).

Data were analyzed using the PC!INFO time-oriented data management and analysis system (Retriever Data Systems, Seattle, WA), which is a modification of the original interactive CLINFO system designed for clinical investigators by the Rand Corporation (Santa Monica, CA) and described by Lincoln and associates [9]. Life table analysis was performed by the Kaplan-Meier method [10], and survival differences were calculated by Gehan's [11] modification of the Wilcoxon test. Group differences in other variables were determined by analysis of variance, the Wilcoxon two-group rank-sum test for nonparametric data, or ² tests.

The follow-up period ranged from 2 to 18 years (mean, 4.3 years). Follow-up at 5 years was 93.4% complete for women and 93.3% complete for men; at 10 years, it was 87.5% complete for women and 89.7% complete for men. Patients were considered lost to follow-up if the health status could not be determined for 2 years after the last follow-up period.

	Results

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
Clinical Data
The mean age (± the standard error) of the women was 64.1 ± 0.3 years versus 60.4 ± 0.3 years in the men (Table 1). Diabetes was present in 28.6% of the women and 16.1% of the men. The history of congestive heart failure was slightly greater and the incidence of previous myocardial infarction at the time of operation was slightly lower in women. The incidence of multivessel or left main artery disease was similar for both men and women, and the number of patients who had had a previous heart operation did not differ significantly between men and women. Women were more likely to have normal ventricular function, but the incidence of an ejection fraction less than 0.4 was the same for both women and men. Isolated coronary artery bypass grafting was performed in 79% of the patients in each group, and the remaining 21% had bypass grafting that was associated with other problems or procedures, such as a left ventricular aneurysm, acute myocardial infarction, peripheral vascular disease, or chronic renal failure.

Hospital Mortality Rate
The hospital mortality was twice as high in women (6.3%) as in men (3.1%) (p = 0.011) (Table 2). The mortality was greater in women having isolated coronary artery grafts, in younger women, and in women with good ventricular function than that in the comparable groups of men. The mortality was not significantly different in women who were 60 years old and older at the time of revascularization and in women with associated problems. The operative mortality in diabetic women was 11.0% (9 of 82), and that in diabetic men was 3.6% (6 of 169). The mortality in nondiabetic patients did not differ significantly between women and men. The causes of operative death were predominantly cardiac related in both women and men.

View larger version (20K): [in this window] [in a new window]   Fig 1. . Probability of survival for all male patients compared with that for all female patients.

View larger version (24K): [in this window] [in a new window]   Fig 2. . (A) Probability of survival for diabetic patients. (B) Probability of survival for nondiabetic patients.

View larger version (24K): [in this window] [in a new window]   Fig 3. . (A) Probability of survival for patients younger than 60 years. (B) Probability of survival for patients 60 years and older.

View larger version (46K): [in this window] [in a new window]   Fig 4. . Health status index for subsets. Shown is the mean for the first 10 postoperative years. (CAB = coronary artery bypass; L main = left main artery disease; LV = left ventricle.)

	Comment

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
The higher morbidity in women who undergo coronary artery bypass procedures is once again documented by this study. As noted in other reports, the differing comorbidities in women and men present at the time of operation appear to explain the findings. In the Coronary Artery Surgery Study (CASS), the increased risk in women was attributed to small stature and small vessel diameter [5]. The operative mortality decreased as both the body size and vessel diameter increased. At the Cleveland Clinic, the operative mortality was found to be twice as high in women, but, when adjusted for the body surface area, the difference was not statistically significant [3]. The long-term survival (5 to 10 years) cited for both the CASS and Cleveland Clinic study did not differ between women and men [3, 12].

Gardner and associates [4], in a study covering the years 1974 through 1983, found the operative mortality in women was higher throughout the study period, until 1983, when parity was achieved (2.4% for women versus 2.6% for men), despite an increasing age at operation in women as compared with men. These authors found that, although advancing age was associated with increased hospital mortality, the difference in women was not statistically significant.

In a group of patients operated on during 1982 through 1987, Khan and associates [6] found that the difference in operative mortality (4.6% in women versus 2.6% in men) was due to greater age and a higher preoperative functional class in the women. King and associates [13] compared women undergoing a first-time coronary artery procedure with men matched for age (mean, 64.2 years). No overall difference in the hospital mortality was found, but women younger than 70 years had an operative mortality rate of 4.2% compared with a rate of 2.2% in men.

We also found that patients operated on more recently tended to be older and were more likely to present with unstable angina or myocardial infarction than those who presented more remotely in time. This did not influence the comparative results between the women and men, because both groups presented with more acute conditions during the later years of the study.

The finding that the probability of survival up to 15 years after operation is less in women is at variance with the findings noted in previous reports. This may be due to the considerably higher incidence of diabetes in our patients than that in either the CASS and Cleveland Clinic series. Diabetes affected 28.6% of the women in the present study, compared with 15.0% for the CASS series and 10.1% for the Cleveland Clinic series. The CASS and Cleveland Clinic study were performed during an earlier period; both primarily included younger patients with good ventricular function. In a study concurrent with ours, Rahimtoola and associates [14] found the 15-year survival to be better in men than in women after isolated coronary artery bypass grafting.

Younger age appeared to have an adverse impact on the survival of women. This finding was also noted for the CASS, in which the 6-year survival in women younger than 50 years was found to be lower than that in men, while older women and men exhibited a similar long-term survival [12]. We also found that the long-term survival in older women and men was similar; even in diabetic women older than 60 years the probability of survival was similar to that of the men (z = 0.88; p < 0.30).

The finding that women experience less satisfactory outcomes than men after coronary artery bypass procedures has been thought to be due to the higher risk profile in women at the time of operation. Our data do not indicate that the women were at higher risk than the men at the time of operation, with the exception of a higher incidence of diabetes in the women. More women than men had normal left ventricular function at the time of operation, and the number of diseased vessels was similar. The incidence of congestive heart failure was slightly higher but the incidence of previous infarction slightly lower in women. Older age in women also did not prove to be a risk factor, as already noted.

Women reported a less satisfactory health status than did men, even among the subsets with a similar long-term survival, such as nondiabetics and those aged 60 years and older. The method we used to assess health status was not elaborate, but simplicity was a necessity in this type of longitudinal analysis, as it is not likely that extensive psychosocial evaluations could have been obtained at annual intervals in such a large series of patients. The consistency of the findings over a long period is important to the validity of the study.

In summary, in our long-term follow-up study of patients who have undergone coronary artery bypass grafting, we found that the hospital mortality, long-term survival, and health status index as determined by annual questionnaires are inferior in women as compared with those in men. The excess mortality appears to be primarily due to a higher incidence of diabetes, particularly in younger women. A lower quality of life may be related to anatomic or metabolic differences that limit the effectiveness of bypass grafts in women.

	Footnotes

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 
Address reprint requests to Dr Carey, 3475 Torrance Blvd, Suite B, Torrance, CA 90503.

	References

Top Footnotes Abstract Introduction Material and Methods Results Comment References

 

1. Kannel WB. Metabolic risk factors for coronary heart disease in women: perspective from the Framingham Study. Am Heart J 1987;114:413–9.[Medline]
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This Article Abstract Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Carey, J. S. Articles by Singer, L. K. M. Search for Related Content PubMed PubMed Citation Articles by Carey, J. S. Articles by Singer, L. K. M.