[Nisoldipine, a new calcium antagonist: its effect on systolic function and relaxation in the dog].

The effect of calcium-blockers on left ventricular (LV) relaxation is still a matter of debate. In 7 open-chest dogs we studied the effect of 0.01 mg/kg Nisoldipine intravenously on LV systolic function and relaxation. LV long and short axes and LV wall thickness were measured by ultrasonic crystals. LV high-fidelity pressure and aortic pressure were recorded at rest, and 2 and 30 min after i.v. Nisoldipine. Partial obstruction of the ascending aorta was performed to keep LV peak systolic pressure close to control values. LV systolic wall stress and LV ejection fraction were calculated in all dogs. The time constant of LV pressure decay (T; ms) was determined from a linear regression of LV pressure and neg. dP/dt. Heart rate and LV end-diastolic pressure remained unchanged following the administration of Nisoldipine. LV peak systolic pressure and wall stress decreased significantly 2 and 30 min after Nisoldipine but were in the normal range with partial obstruction of the ascending aorta. Max. dP/dt decreased slightly although not significantly after Nisoldipine. LV ejection fraction increased, however, significantly from 30% to 39% at 2 min and to 35% at 30 min after Nisoldipine. The time constant T increased from 27 ms to 40 ms (P less than 0.05) at 2 min and amounted to 28 ms at 30 min following Nisoldipine. It is concluded that Nisoldipine is associated with a persistent decrease of LV afterload and a transitory increase in T.(ABSTRACT TRUNCATED AT 250 WORDS)