Physiologic Behavior of the in Situ Papillary Muscles

Distention of the intact right ventricular papillary muscles induced both mechanical and electrophysiologic changes in the whole heart. Severe dysrhythmia accompanied tension exerted upon the right, but not upon the left ventricular chordae tendineae. The right ventricular papillary muscles contain numerous receptors, stimulation of which induces marked changes in afferent impulse traffic in the cardiac nerves. Local papillary muscle contractile force was initially depressed and then elevated while that of distant myocardial segments was augmented during local papillary muscle distention. These responses were shown to be influenced by both sympathetic and parasympathetic cardiac nerves. A physiologic cardio-cardiac neural control mechanism is proposed to account for these dynamic cardiac events.