Estimated contribution of coronary artery bypass graft surgery to the decline in coronary heart disease mortality: the Minnesota Heart Survey.

OBJECTIVES

This study assessed the possible contribution of coronary artery bypass graft surgery to the decline in coronary heart disease mortality in the Minneapolis-St. Paul metropolitan area population between 1970 and 1984.

BACKGROUND

Coronary artery bypass graft surgery is a major contemporary therapeutic approach for coronary heart disease. Its use has increased over the past two decades because it provides relief of symptoms and, in certain circumstances, prolongs life. During the period that age-adjusted coronary heart disease mortality has decreased, the use of coronary artery bypass graft surgery has increased dramatically, suggesting a relation.

METHODS

All 30- to 74-year old Minneapolis-St. Paul area residents undergoing coronary artery bypass graft surgery between 1970 and 1984 (9,548 patients) were registered; their medical records were abstracted; and their survival was ascertained. These data were used in a medical survival probability model using a multivariate analytical approach developed from registries of patients treated medically. The model assumed that coronary artery bypass graft surgery was not available. Two annual mortality rates were compared: the observed Minneapolis-St. Paul annual coronary heart disease mortality rate and the modeled annual coronary heart disease mortality rate. The difference between these rates was the estimated contribution of coronary artery bypass graft surgery to the decline in coronary heart disease mortality rates.

RESULTS

Between 1970 and 1984, the estimated surgical contribution increased from 0.2% (increased mortality) to +6.6% of the annual decrease in Minneapolis-St. Paul coronary heart disease mortality.

CONCLUSIONS

Between 1970 and 1984, the contribution of coronary artery bypass graft surgery to the decline in coronary heart disease mortality, although small, gradually increased. This change appeared to be related to an increased frequency of coronary artery bypass graft surgery, improved operative mortality and changes in the clinical mix of surgical patients.