To elucidate the hemodynamic responses to sublingual nifedipine administration during exercise and recovery in congestive heart failure, 16 patients with dilated cardiomyopathy (DCM) and 11 controls were studied using supine bicycle exercise testing. The cardiac index (CI) was measured at rest, at peak exercise and successively during recovery by the thermodilution method. The heart rate (HR), mean blood pressure (mBP) and mean pulmonary arterial pressure (mPAP) were measured every minute. The same exercise load and hemodynamic measurements were repeated about 30 min after the sublingual administration of 10 mg nifedipine. The recovery slope in each parameter was analyzed using an exponential function (Cp = C1ekt). The regression coefficient in each parameter was defined as a CI slope, an HR slope, an mBP slope and an mPAP slope. Before the administration of nifedipine, CI at peak exercise was lower, mPAP during recovery was persistently higher and the CI slope was more blunt in DCM patients, compared with those of the controls. With the administration of nifedipine, CI and HR increased or tended to increase, mBP decreased throughout the exercise and recovery, and mPAP decreased at rest, at peak exercise and one min after exercise in the controls. In DCM patients, however, the CI increased, mBP and mPAP decreased nearly throughout the exercise and recovery, while HR increased throughout the exercise and recovery, except at peak exercise. The CI, HR and mPAP slopes were blunted in the controls; whereas, each slope showed no change in DCM patients. These results suggest that sublingual nifedipine administration can reduce both the preload and afterload, and increase CI throughout exercise and recovery without significant alteration in the recovery course.(ABSTRACT TRUNCATED AT 250 WORDS)