Differential effects of isradipine and atenolol on peripheral hemodynamics and arterial compliance

In a double-blind parallel-group randomized study, 28 patients with essential hypertension (World Health Organization class I/II) were allocated in equal numbers to one of two groups for treatment with either isradipine 5 to 20 mg twice daily or atenolol 50 to 100 mg once daily. At the end of the study, 12 patients were evaluable in the isradipine group and nine in the atenolol group. Assessments at baseline and after 20 weeks of treatment included arterial and venous compliance, mean peripheral perfusion pressure, heart rate, and digital vascular resistance using photoplethysmography. Isradipine had a direct relaxing effect on the arterioles, revealed by a significant increase in arterial compliance and a concomitant normalization of the digital vascular resistance. Atenolol had no significant effect on these parameters but, as expected, it lowered the heart rate, which was not affected by isradipine in the long term. The venous compliance remained low in both groups and, since isradipine--unlike atenolol--is known to have venodilating properties in vitro, its lack of effect in vivo is most likely due to reflex activation of sympathetically mediated venous tone. Because of the preference of isradipine for the arterial side of the peripheral vascular tree, the mean peripheral perfusion pressure remained higher in this group than in the atenolol group, although central systemic blood pressure was lowered equally and satisfactorily in both groups.