STUDIES ON DIGITALIS. IV. OBSERVATIONS IN MAN ON THE EFFECTS OF DIGITALIS PREPARATIONS ON THE CONTRACTILITY OF THE NON-FAILING HEART AND ON TOTAL VASCULAR RESISTANCE

Abstract

The direct effects of two digitalis preparations on the contractile force of the heart were studied by means of the Walton-Brodie strain gage arch in 21 patients who had never experienced congestive heart failure. Fourteen patients with either atrial septal defect or pulmonic stenosis, studied during cardiopulmonary bypass, were given 0.5 to 1.5 mg of acetylstrophanthidin, a dose which averaged 0.026 mg/kg body weight. This resulted in an increase in contractile force which ranged from 16 to 327% and averaged 89% of the contractile force measurement prior to digitalization. In 3 patients who received an average dose of 0.022 mg/kg of lanatoside C during cardiopulmonary bypass, the right ventricular contractile force increased by an average of 31% of control levels. In an attempt to study the response of a ventricle which had not been subjected to an abnormal hemodynamic burden for a prolonged period of time, left ventricular contractile force was recorded immediately after mitral valvulotomy in 3 patients. Acetylstrophanthidin increased contractile force an average of 24% of the control levels. The administration of the digitalis preparations to patients on cardiopulmonary bypass at a constant perfusion rate permitted study of the direct effects of these drugs on systemic vascular resistance. Acetylstrophanthidin resulted in a brief increase in systemic vascular resistance which averaged 23% and lanatoside C resulted in an average increase of 14% of the control levels. It is concluded that these digitalis preparations augment the contractile force of the non-failing human heart and constrict the systemic vascular bed.