Impact of number of vessels disease on outcome of patients with stable coronary artery disease: 5-year follow-up of the Medical, Angioplasty, and bypass Surgery study (MASS).

OBJECTIVE To evaluate whether the number of vessels disease has an impact on clinical outcomes as well as on therapeutic results accordingly to medical, percutaneous, or surgery treatment in chronic coronary artery disease. METHODS We evaluated 825 individuals enrolled in MASS study, a randomized study to compare treatment options for single or multivessel coronary artery disease with preserved left ventricular function, prospectively followed during 5 years. The incidence of overall mortality and the composite end-point of death, myocardial infarction, and refractory angina were compared in three groups: single vessel disease (SVD n=214), two-vessel disease (2VD n=253) and three-vessel disease (3VD n=358). The relationship between baseline variables and the composite end-point was assessed using a Cox proportional hazards survival model. RESULTS Most baseline characteristics were similar among groups, except age (younger in SVD and older in 3VD, p<0.001), lower incidence of hypertension in SVD (p<0.0001), and lower levels of total and LDL-cholesterol in 3VD (p=0.004 and p=0.005, respectively). There were no statistical differences in composite end-point in 5 years among groups independent of the kind of treatment; however, there was a higher mortality rate in 3VD (p<0.001). When we stratified our analysis for each treatment option, bypass surgery was associated with a lower number of composite end-point in all groups (SVD p<0.001, 2VD p=0.002, 3VD p<0.001). In multivariate analysis, we found higher mortality risk in 3VD comparing to SVD (p=0.005, HR 3.14, 95%CI 1.4-7.0). CONCLUSION Three-vessel disease was associated with worse prognosis compared to single- or two-vessel disease in patients with stable coronary disease and preserved ventricular function at 5-year follow-up. In addition, event-free survival rates were higher after bypass surgery, independent of the number of vessels diseased in these subsets of patients.