This study sought to investigate, in patients with idiopathic-dilated cardiomyopathy, the clinical and prognostic value of a Doppler-derived index of myocardial function that combines systolic and diastolic time intervals of the left heart cycle. The Doppler index was measured in 75 patients (aged 61 +/- 13 years; 45 men and 30 women) in sinus rhythm and 75 age- and sex-matched controls. Ejection time was measured from the left ventricular outflow Doppler signal. The sum of isovolumic times was obtained by subtracting the ejection time from the interval between cessation and onset of mitral inflow measured from the mitral inflow velocity profile. The index was the sum of isovolumic times divided by ejection time. The values of the Doppler index in patients with idiopathic-dilated cardiomyopathy (0.85 +/- 0.32) were significantly higher than values in controls (0.37 +/- 0.08, p < 0.001). During follow-up of 5 years, 1 patient underwent cardiac transplantation and 36 patients died, 29 of cardiac, 5 of noncardiac, and 2 of unknown causes. Univariate analysis demonstrated that the Doppler index (chi-square = 18.3, p < 0.001), ejection fraction (chi-square = 15.2, p <0.001), symptom status (chi-square = 9.2, p = 0.002), and mitral deceleration time (chi-square = 5.2, p = 0.02) were significant predictors of outcome. However, multivariate stepwise analysis of these variables showed that the Doppler index (chi-square = 10.7, p = 0.001) and ejection fraction (chi-square = 6.7, p = 0.01) were the most significant independent predictors of outcome. The Doppler index reflects disease severity and has incremental prognostic value in dilated cardiomyopathy. Ease of use, nongeometric dependency, excellent separation of clinical groups, and a strong relation to outcome enhance its appeal.