Coronary Artery Surgery Study (CASS)

BACKGROUND:

Although it was generally agreed that many patients with severe angina pectoris improved symptomatically after coronary artery surgery, there was less consensus concerning, for example, other effects of the procedure, such as its long-term benefit and the criteria for patient selection. In addition, there were fewer data and less agreement on the effects and proper role of this procedure in other clinical circumstances. Both the surgical procedure and the prior diagnostic procedures represented substantial costs in both monetary and manpower terms; moreover, they entailed morbidity and mortality risks.

There existed an urgent need for reliable and quantitative information regarding the effects of coronary artery surgery in patients with ischemic heart disease. To be meaningful, these data had to be set into the perspective of the clinical course of such patients under medical treatment.

This assessment presupposed a meaningful classification of these patients and of the therapeutic interventions as well as evaluations of the effects of surgical and medical regimens in terms of mortality, the quality of life, and objective hemodynamic and other physiological measurements. Only such information could provide sufficient background for determining the suitability of coronary artery surgery for a particular patient.

In 1972, the National Heart and Lung Advisory Council identified these questions as topics of high priority, and the National Heart and Lung Institute established an Ad Hoc Policy Advisory Board on Coronary Artery Surgery to assist it in developing a program of research activities. In its report, the Board noted a 'critical need for objective data on the long- and short-term effects of coronary artery surgery.' Requests for proposals were issued to carry out the recommendations of the Board.