Left ventricular (LV) diastolic function is often impaired in coronary artery disease (CAD). To assess whether verapamil could improve LV diastolic properties, 12 patients with CAD undergoing right- and left-sided cardiac catheterization, as well as simultaneous radionuclide angiography, were studied before and during intravenous administration of verapamil (0.1 mg/kg as a bolus followed by 0.007 mg/kg/min). The heart rate was kept constant by atrial pacing in both studies. LV pressure-volume relations were obtained. Verapamil decreased LV systolic pressure (130 +/- 22 to 117 +/- 16 mm Hg, p less than 0.01) and the end-systolic pressure/volume ratio (2.4 +/- 1.3 to 1.6 +/- 0.5 mm Hg/ml, p less than 0.05), and increased LV end-diastolic (13 +/- 4 to 16 +/- 4 mm Hg, p less than 0.02) and pulmonary capillary pressures (10 +/- 5 to 12 +/- 5 mm Hg, p less than 0.005). Despite such negative inotropic effects, cardiac index increased (3.4 +/- 0.7 to 3.9 +/- 0.6 liters/min/m2, p less than 0.02). The time constant of isovolumic relaxation shortened (63 +/- 14 to 47 +/- 9 ms, p less than 0.02); peak filling rate increased (370 +/- 155 to 519 +/- 184 ml/s, p less than 0.001; 2.6 +/- 1.1 to 3.3 +/- 0.9 end-diastolic counts/s, p less than 0.02; and 4.1 +/- 1.6 to 5.5 +/- 1.5 stroke counts/s, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)