The effects of verapamil were compared with those of nitroprusside at matched mean arterial pressures and heart rates in 10 symptomatic hypertensive patients during cardiac catheterization. Simultaneous radionuclide angiography and micromanometer pressure measurements were obtained to assess left ventricular pressure-volume relations. Compared with control conditions, verapamil increased left ventricular end-diastolic volume index from 57 ± 16 to 70 ± 28 ml/m2 (p = 0.05) without a significant increase in left ventricular end-diastolic pressure (from 10 ± 4 to 13 ± 6 mm Hg). Despite a downward and rightward shift in the end-systolic pressure-volume relation indicating negative inotropic effects, ejection fraction did not decrease significantly (from 52 ± 9% to 46 ± 9%); cardiac index and stroke volume index remained unchanged. The change in stroke volume index with verapamil was directly related to the magnitude of change in end-diastolic volume index (r = 0.82, p < 0.005), suggesting that the increase in enddiastolic volume did not arise purely from negative inotropic effects. Systemic vascular resistance index decreased from 42 ± 8 to 34 ± 7 mm Hg-min-m2/liter (p < 0.05). In contrast, nitroprusside decreased left ventricular end-diastolic volume index from 57 ± 16 to 41 ± 10 ml/m2 (p < 0.05), cardiac index from 3.2 ± 0.7 to 2.8 ± 0.6 liters/min per m2 (p < 0.05) and stroke volume index from 28 ± 6 to 24 ± 5 ml/m2 (p < 0.01), with no change in systemic vascular resistance index (40 ± 10 mm Hg·min·m2). The end-systolic pressure-volume relation shifted downward and leftward in all patients, stemming from altered left ventricular loading. Thus, in equihypotensive doses, verapamil and nitroprusside have markedly different effects on left ventricular function. The peripheral vasodilation and apparent improvement in left ventricular filling during verapamil balanced the negative inotropic effects, resulting in maintenance of stroke volume and cardiac index. The primary hypotensive effect of verapamil was a decrease in systemic vascular resistance, whereas that of nitroprusside was a decrease in cardiac index stemming from reduced left ventricular preload.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine