Evidence for left ventricular diastolic suction in closed-chest dogs

¹ Departments of Physiology and Pharmacology, Medical College of Georgia, Augusta, Georgia

The question of ventricular filling by "suction" was investigated by recording the transmural ventricular pressure in normally breathing animals who had recovered from surgery. This transmural pressure was recorded as the difference between the thoracic pressure and the intraventricular pressure. It was considered positive whenever the ventricular pressure exceeded the thoracic pressure as is the case during systole, and negative when it was less than the thoracic pressure. During diastole the difference between these pressures are always small (±10 mm Hg or less). In the normal untraumatized animal it is zero or positive (filling by venous pressure). After the animal deteriorates from repeated experiments it may become negative, (filling by an action of the ventricular wall or suction). This suction is greater as a result of conditions which interfere with venous return and diminish the size of the ventricles by x-ray (mitral stenosis or bleeding). The force of suction is lessened after transfusions which increase the size of the ventricles. Considerations are advanced for believing that the suction force originates in elastic recoil of the ventricular wall and that it is not clearly an important factor in the mechanism of cardiac pumping.