Studies on Cardiac Dimensions in Intact, Unanesthetized Man

Abstract

The effects on ventricular dimensions of intact, unanesthetized patients of isoproterenol, a drug that stimulates beta adrenergic receptors, and of methoxamine, an agent that stimulates alpha adrenergic receptors, were studied by means of a cineradiographic technic. The administration of isoproterenol to 13 patients consistently resulted in a decline in the end-systolic dimensions of both ventricles. A smaller and less consistent decrease in ventricular end-diastolic dimensions was noted. In contrast, the administration of methoxamine resulted in an increase of ventricular end-diastolic dimensions in all 10 patients studied. Left ventricular end-systolic dimensions increased during methoxamine infusion in the eight patients in whom the measurements were made, but changes in right ventricular end-systolic dimensions were inconsistent. The alterations in heart rate induced by isoproterenol and methoxamine could account only in part for the observed changes in ventricular dimensions. It is anticipated that the experimental approach used in this study, that is, the measurement of ventricular dimensions in intact, unanesthetized human subjects, will help to provide a more complete analysis of the action of drugs on the circulation of man.