Coronary artery bypass surgery in women and in men; early and long-term results. A study of the Norwegian population adjusted by age and sex.

OBJECTIVE: We wished to analyse early mortality, postoperative low-output syndrome needing intra-aortic balloon pumping support (IABP), total mortality, recurrent angina pectoris and total non-fatal myocardial infarction in women compared with men. Also, the standard mortality ratio (SMR) was estimated to compare the mortality data to the general Norwegian population of comparable sex and age.

METHODS: A total of 1025 patients; 113 women and 912 men, were submitted to coronary artery bypass surgery at Rikshospitalet, Oslo between August 1982 and December 1986. The patients were followed up until the 1st of January 1993, representing a mean follow-up time of 7.4 years. An exposed/non-exposed cohort study design was used. A power study was carried out. The standardized mortality ratios for women and men were calculated after adjusting for age and sex.

RESULTS: Crude odds ratio (ORC) of early mortality was 2.0 with a 95% confidence limit (CL95%) of 0.7-5.4. Odds ratio of low output syndrome needing intra-aortic balloon support was 1.7 (CL95% = 0.8-4.2). Statistical significance was not achieved for these end-points. Women did not run an increased hazard of total mortality (ORC = 0.9; CL95% = 0.5-1.5), recurrent angina pectoris (ORC = 1.4; CL95% = 0.8-2.4) or of total non-fatal myocardial infarction (ORC = 0.8; CL95% = 0.4-1.6) when compared with men. Adjusting for confounders did not significantly alter the results. When matched on sex and age and compared to the normal Norwegian population, we found an increased SMR in both men (2.5; CL95% = 2.2-2.9) and women (4.1; CL95% = 2.2-4.9).

CONCLUSION: The risk of early mortality and low-output syndrome needing intra-aortic balloon support tended to be higher in women compared with men. Women did not run an increased risk of total mortality, recurrent angina or of total non-fatal myocardial infarction. The standard mortality ratio was increased in both men and women, but in particular higher in women, suggesting a more aggressive course of coronary artery disease in operated women than in operated men. However, this difference did not show in the long term follow-up, due to the beneficial effect of coronary artery bypass surgery in both men and women.