THE CARDIODYNAMIC CHANGES IN THE AORTA AND LEFT VENTRICLE DUE TO STENOSIS OF THE AORTA

Abstract

An analysis was made of the effects produced by stenosis of the aorta in anesthetized dogs based on optical pressure curves recorded simultaneously from the aorta and left ventricle. Stenosis of the aorta increased the height of the left ventricular pressure curve, made the summit more peaked, increased the duration of the curve, and augmented the steepness of the ascent and descent. No vibrations were superimposed however. The changes are shown to be partly the result of the constriction itself which decreases the conversion of potential mechanical energy to kinetic energy of flow and partly the result of the increase in the diastolic stretch of the ventricle. The pressure curve of a completely isometric contraction of the right ventricle is reproduced. The similarity in the fundamental contour of the aortic and left ventricular curves during ejection disappears when a stenosis is created; the amplitude and the gradients of the ascent change in opposite directions and the peaks no longer coincide. The aortic pressure curve shows the following changes during stenosis: decreased pulse amplitude, lowered pressure levels, prolonged ejection time, diminished gradient of ascent, less decisive in-cisura and after-vibration, superimposition of systolic (and early diastolic) vibrations on the curve, appearance of a sharp vibration low down on ascent. The aortic curve resembles the subclavian pulse optically recorded in clinical cases of aortic stenosis. The sharp vibration on the ascent changes its position with different degrees of stenosis. It is a forced vibration probably created by the suction action of the suddenly produced axial stream beyond the constriction. The importance in this vibration as the anlage of the radial pulse is again emphasized.