Comparison of the hemodynamic effects of five calcium channel blockers at rest and during exercise in essential hypertension.

Dihydropyridine and verapamil-like calcium channel blockers reduce blood pressure (BP) in essential hypertension (EH) but have different effects on heart rate (HR) at rest. This study compares the HR and hemodynamic responses to exercise of long-term treatment with nifedipine, nisoldipine, verapamil, tiapamil and diltiazem in five groups of patients with mild and moderate EH (diastolic BP ranging 100-120 mmHg). In a total of 76 patients (mean age 43 years) BP was measured intraarterially, cardiac output by dye dilution (Cardiogreen) and HR by electrocardiogram. Acutely HR and cardiac index (CI) rose (9 and 12%) while BP and total peripheral resistance index (TPRI) were reduced (9 and 19%). After one year calcium channel blockade intraarterial pressure at rest sitting fell from 172/105 to 150/91 mmHg (13%) and at 100 W exercise from 205/109 to 188/97 mmHg (10%). HR remained unchanged in the dihydropyridine groups (range +/- 3%) in all situations while it invariably fell (range 3 to 15%) in the groups treated with verapamil-like calcium blockers. The fall in HR was greater during exercise than at rest (mean 10% vs 6%). With these drugs stroke volume (SV) tended to increase (range 1 to 10%) while it remained unchanged in the dihydropyridine groups. Only minor changes were seen in CO. In all groups the TPRI fell, averaging 15% at rest and during exercise. Thus, the verapamil-like calcium blockers induce a negative chronotropic effect that is enhanced during work, but the cardiac pump function is preserved by a compensatory increase in SI. Independent on the cardiac responses both groups of calcium blockers lower BP by peripheral vasodilatation both at rest and during exercise.