Cardiac hypertrophy and left ventricular end-diastolic stress.

Equatorial and longitudinal left ventricular wall stress were calculated at end-diastole in a group of 66 patients in sinus rhythm. Thirty-one patients had volume overload of the left ventricle: six with acute and 21 with chronic aortic incompetence, and four with chronic mitral incompetence. Another six patients had aortic stenosis and 25 had congestive cardiomyopathy. Four patients served as controls. Stress was calculated using a thick-walled ellipsoid model. In patients with volume overload and congestive cardiomyopathy, ventricular dilatation was accompanied by an appropriate increase in wall thickness so that the "stress conversion factor" (the factor relating pressure to stress) was normal and absolute stress depended on end-diastolic pressure. In pressure overload of the left ventricle (aortic stenosis), the increase in wall mass reduced the stress conversion factor so that aboslute fiber stress was normal. These data support the hypothesis that muscle fiber stress may be an important determinant of left ventricular hypertrophy.