Regional variations in calculated diastolic wall stress in rat left ventricle.

Principal radii of curvature and wall thickness were measured at the apex and three other loci on the free wall of the left ventricle in 16 rat hearts that had been fixed at end-diastolic pressure. The law of Laplace was applied to calculate the mean tensile stress at each locus. No significant variation was found among the nonapical loci, but apical stress was approximately twice the stress calculated for any nonapical locus. The higher stresses that must be borne by the apex may be a predisposing factor for apical aneurysm in certain cardiomyopathies such as Chagas' disease. These higher stresses may also help to promote apical aneurysms in patients with ischemic heart disease.