Hemodynamic Effects of Isradipine and Nifedipine in Chronic Sustained Hypertension

Abstract

As isradipine is known to be less cardiodepressant than nifedipine, myocardial wall stress--an important determinant of cardiac oxygen demand--may also be more favorably influenced by isradipine. Therefore, the acute effects of an intravenous (i.v.) infusion of isradipine (0.4 mg) vs. nifedipine (2.0 mg) on cardiac hemodynamics and systolic wall stress were investigated in a crossover study of 12 hypertensive patients. Vasodilation-induced reflex activation was limited by pretreatment with i.v. propranolol at 0.1 mg/kg of body weight. The hemodynamic parameters measured were statistically comparable at baseline and after propranolol with both calcium antagonists, as was blood pressure reduction. However, the end-systolic volume decreased with isradipine, but not with nifedipine [before: 69 +/- 7.0 ml (mean +/- SEM); after: 61 +/- 6.1 ml; 2p less than 0.01 vs. before: 62 +/- 6.1 ml; after: 64 +/- 7.0 ml; NS, (difference between changes in response to treatments: 2p less than 0.05)]. The ejection fraction increased only with isradipine vs. nifedipine [before: 48 +/- 2.3%; after: 54 +/- 2.3%; 2p less than 0.001 vs. before: 52 +/- 2.0%; after: 52 +/- 2.3%; NS (difference between changes in response to treatments: 2p less than 0.05)]. Systolic wall stress decreased significantly more with isradipine than with nifedipine [before: 2,767 +/- 231; after: 2,153 +/- 162 relative units; 2p less than 0.001 vs. before: 2,636 +/- 212; after: 2,310 +/- 199 relative units; 2p less than 0.05 (difference between changes in response to treatments: 2p less than 0.05)]. These results suggest that isradipine, given acutely, unloads the heart more than does nifedipine.