Comparative analysis of cardiac function, geometry, energetics and coronary reserve in hypertensive heart disease

Abstract

In essential hypertension ventricular function is determined primarily by the degree of hypertrophy (myocardial factor) and by the organic complications in the coronary artery (coronary factor). Ventricular function is inversely correlated with ventricular size and systolic wall stress, inasmuch as ventricular function diminishes when these two variables increase. Even the young hypertensive heart of normal size with no angiographic abnormalities appears to be prone to ischemia, because the coronary reserve is seriously limited even in the absence of coronary stenosis. Unlike ventricular distensibility, myocardial compliance may be normal even in the presence of pronounced myocardial hypertrophy. As myocardial compliance decreases, systolic wall stress increases and ventricular function is reduced. The hypertensive heart, the most common form of an irregular hypertrophy of the ventricular wall, is found in 14% of such cases. Analysis of the degree of hypertrophy shows that the hypertrophy can be inappropriately high (high mass-to-volume ratio, reduced wall stress), appropriate, or inappropriately low (normal mass-to-volume ratio, increased wall stress). Coronary reserve is reduced even in hypertensive hypertrophy without evidence of coronary artery disease. MVO2 per mass unit was directly correlated with systolic wall stress per cross-sectional area of the left ventricular wall. It is concluded that the appropriateness of left ventricular hypertrophy, as a result of mass-to-volume ratio and stress, is a major determinant of left ventricular performance, of coronary blood flow, and of myocardial oxygen consumption. Pharmacotherapeutical means of reversing cardiac hypertrophy (prazosin, clonidine, enalapril, and nifedipine) were analyzed in concentrically, as well as eccentrically, hypertrophied left ventricles. Regression of cardiac hypertrophy, i.e. therapeutic intervention on a critical precursor of hypertensive congestive heart failure, can be obtained by various antihypertensive agents. Prazosin, calcium channel blockers and angiotensin-converting enzyme inhibitors as well as a combined treatment regimen using alpha-receptor blockers together with diuretics and vasodilators can all induce regression of hypertrophy associated with an improvement in left ventricular function. Moreover, an improved coronary reserve may reduce the ischemic risk of the hypertrophied myocardium. However, not all antihypertensive drugs seem equally effective in bringing about coronary regression of left ventricular hypertrophy. No regression or little regression has been found with diuretic monotherapy despite a satisfactory reduction in blood pressure.(ABSTRACT TRUNCATED AT 400 WORDS)