Cardiac rhythm in hypertension assessed through 24 hour ambulatory electrocardiographic monitoring. Effects of load manipulation with atenolol, verapamil, and nifedipine.

Abstract

In systemic hypertension, left ventricular wall stress (afterload) is reduced and function enhanced, compared with normal, in the presence of concentric hypertrophy; the opposite occurs when hypertrophy is combined with dilatation. The hypothesis that cardiac rhythm may be related in part to the interacting variables, i.e., left ventricular structure, afterload and function, was studied. A total of 85 primary hypertensives were divided into 3 groups: group 1, 24 cases with normal sized heart; group 2, 33 cases with concentric hypertrophy; and group 3, 28 cases with hypertrophy and dilatation. Cardiac rhythm through 24 h ambulatory ECG monitoring and end-systolic left ventricular circumferential wall stress were investigated before and after 7 days of treatment with atenolol, verapamil and nifedipine in groups 1 and 2, and with the 2 Ca antagonists in group 3. Atrial and ventricular extrasystoles were recorded in 75-100% of the subjects in the control group (13 normotensives) and in the hypertensive groups. Average 24 h atrial ventricular extrasystoles in group 1 and ventricular extrasystoles in group 2 were similar to normal before treatment and were not affected by drugs; changes in circumferential wall stress with treatment were comparable. In group 2 the number of atrial extrasystoles in 24 h was significantly higher than in all the other groups. They were not influenced by changes in wall stress, and were interpreted as related to the atrial booster pump action in the presence of concentric hypertrophy. In group 3 a great number of ventricular extrasystoles was associated with the highest baseline left ventricular afterload; circumferential wall stress and ventricular extrasystoles were poorly affected by verapamil; the remarkable circumferential wall stress reduction caused by nifedipine was paralleled by an obvious decrease in ventricular extrasystoles. In systemic hypertension, a relation may exist between cardiac structure, load and rhythm, and ventricular arrhythmias may benefit from effective left ventricular unloading.