The availability of circulatory support devices has increased the importance of accurately identifying patients at risk for hemodynamic compromise during percutaneous transluminal coronary angioplasty (PTCA). Accordingly, prospective evaluation of 3 criteria to predict hemodynamic compromise (defined as a decrease in systolic blood pressure > or = 20 to < 90 mm Hg during balloon inflation) in 157 patients (group A) undergoing PTCA was performed. Left ventricular ejection fraction < 35% had a sensitivity of 13% and a specificity of 95%. Greater than 50% of the myocardium at risk was associated with a sensitivity of 31% and a specificity of 85%. The angiographer's assessment of high risk for hemodynamic compromise had the highest sensitivity of 56% and a specificity of 86%. The clinical and angiographic characteristics of these patients were reviewed to identify risk factors retrospectively. Multivariate analysis of 28 variables identified multivessel disease, diffuse disease, myocardium at risk, and stenosis before PTCA as independent predictors of hemodynamic compromise. With use of this analysis, a 13-point weighted scoring system was created based on the regression of coefficients of the variables. Defining high risk for hemodynamic compromise as a risk score > or = 4, the sensitivity of this criterion in group A patients was 81% and the specificity was 74%. The scoring system was then prospectively applied to 61 consecutive patients (group B) undergoing PTCA. In using a risk score > or = 4 to define high risk, this scoring system had a sensitivity of 92% and a specificity of 92%.(ABSTRACT TRUNCATED AT 250 WORDS)