This study was designed to clarify the validity of Doppler indices for assessment of the severity of congestive heart failure in patients with dilated cardiomyopathy. Left ventricular (LV) and right ventricular (RV) Doppler indices, defined as the sum of isovolumic contraction time and relaxation time divided by the ejection time, were obtained in 30 normal; subjects and 35 patients with ischemic or idiopathic dilated cardiomyopathy. We analyzed the correlation between New York Heart Association (NYHA) functional class, right-sided cardiac pressure, and the Doppler indices. Patients with dilated cardiomyopathy revealed significantly higher LV and RV Doppler indices than normal subjects; however, the LV Doppler index did not correlate significantly with NYHA functional class or right-sided cardiac pressure. On the other hand, the RV Doppler index correlated significantly with NYHA functional class (rs = 0.83, P < 0.001), pulmonary capillary wedge pressure (r = 0.80, P < 0.001), pulmonary artery systolic pressure (r = 0.81, r < 0.001) and pulmonary artery diastolic pressure (r = 0.77, P < 0.001). Both RV isovolumic contraction and relaxation time also correlated significantly with right-sided cardiac pressure. In 12 patients who improved from NYHA III-IV to I-II after treatment, the RV Doppler index decreased from 0.84 +/- 0.25 to 0.33 +/- 0.10 (P < 0.001), while the LV Doppler index did not change significantly (0.72 +/- 0.27 to 0.68 +/- 0.23, P = 0.53). These results suggest that the RV Doppler index is useful fur assessment of the severity of congestive heart failure in patients with dilated cardiomyopathy.