A Randomized Trial of Coronary Artery Bypass Surgery

TLDR

The Coronary Artery Surgery Study (CASS) compared medical versus surgical treatment in selected patients with chronic, stable coronary artery disease. The study followed a subset of 160 patients with reduced ventricular function (ejection fraction 0.34–0.50) randomized to medical therapy (82) or surgery (78) over an average of seven years, with baseline characteristics comparable between groups. Seven‑year survival was higher in the surgical group (84 % vs 70 %) and, among patients with triple‑vessel disease, survival was 88 % versus 65 % for surgery versus medical therapy, indicating improved outcomes with bypass surgery.

Abstract

The Coronary Artery Surgery Study (CASS) was designed to compare medical and surgical treatment of selected patients with chronic, stable coronary artery disease. This report concerns a subset of patients with reduced ventricular function. Of 780 patients randomly assigned to medical or surgical treatment, 160 had ejection fractions above 0.34 but below 0.50 at base line and have been followed for an average of seven years. Eighty-two patients were assigned to medical therapy, and 78 to surgery; the two groups were comparable at base line with regard to prognostically important variables. At seven years, 84 per cent of patients in the surgical group were alive, as compared with 70 per cent of the medical group (P = 0.01). Nearly half the patients with impaired ventricular function had triple-vessel disease at entry; at seven years, observed survival in this group was 88 and 65 per cent for those assigned to surgical and medical treatment, respectively (P = 0.009). Survival of patients with single-vessel or double-vessel disease was similar in the two treatment groups. We conclude that patients with triple-vessel disease and ejection fractions higher than 0.34 but lower than 0.50 appear to have improved seven-year survival with elective bypass surgery.