Mechanics of the interventricular septum

Abstract

Dr. Eldon Smith has just pointed out that the interventricular septum is a compliant membrane during diastole. Although stiffer during systole, the shape and position of the septum is also determined by the instantaneous transseptal pressure gradient. I’ll try to show that contractions of septal muscle fibers influence cardiac pump-function depending on the end-diastolic position of the septum and illustrate this by presenting examples from selective right- and left ventricular volume loading. The experiments I’ll refer to were performed at the Institute for Experimental Medical Research, University of Oslo, Norway. The results have been published by Dr. Molaug and co-workers. We used mongrel dogs, anesthetized with sodium pentobarbital. The chest was opened and segment lengths were recorded in the right and left ventricular free walls and the interventricular septum. Pairs of piezoelectric crystals were sewn into midwall positions, and segment lengths were recorded by an ultrasonic technique.