Negative Ventricular Diastolic Pressure in Beating Heart Studied in vitro and in vivo. ∗

Abstract

Since the classic studies of Harvey(1) it has been generally accepted that diastolic filling of the heart resulted from venous return and auricular contraction. While the senior author(2) was studying the effects of anoxia and work on the glycogen content of the rat heart, it was necessary to make observations on the excised heart beating in saline. With each systole it was observed that fluid ejection from the aorta resulted in the jet propulsion of the heart in the solution and it was obvious that the heart must draw in fluid in each diastole to make possible subsequent systolic ejection; thus it was concluded that part of systolic energy was dissipated in diastole(2).

This paper presents the results of a study of pressure changes in intact and excised heart during systole and diastole.

Materials and methods. White rats weighing 300 to 450 g were anesthetized with pentobarbital 6 mg/100 g. The thorax was rapidly opened and the intact heart removed. A 20 gauge needle was inserted into the left ventricle and the needle connected to a three-way stop cock on a Statham strain gauge so that opening the stop cock recorded hydrostatic zero. The heart was placed in a pottery pie plate filled with saline. The three limb leads of the EKG were placed equidistant around the perimeter of the plate with the electrodes immersed in solution. Pressures and EKG were recorded with an Oscillograph. When desired the auricles were opened widely or excised with a pair of scissors. In vivo studies were performed on dogs anesthetized with pentobarbital. Artificial respiration was administered through an intratracheal tube and the chest was widely opened. Umbilical tape was placed around the superior vena cava and azygos veins.