Shape and Volume Changes During "Isovolumetric Relaxation" in Normal and Asynergic Ventricles

Clinically suspected coronary artery disease was assessed in 52 patients by 16-mm biplane left ventriculography. Outward movement of the left ventricular wall was observed prior to mitral valve opening in normal patients and those with coronary artery disease. In the normal ventriculogram, outward movement was usually visible in the anterior wall and the apex. In the asynergic ventricle, the outward movement almost invariably occurred at the region of optimal contraction. Outward movement of the ventricular wall during protodiastole and isovolumetric relaxation was accompanied by a significant volume increase over the end-systolic volume. The volume increase was greater in the abnormal than in the normally contracting ventricle.The altered ventricular volume was probably associated with the return to the ventricle of blood contained between the patent aortic leaflets at the end of ventricular ejection. This event occurs during aortic valve closure when ventricular pressure is falling more rapidly than aortic pressure. It accounts for the alteration in volume between end ejection and pre-mitral valve opening.The stroke volume, which is generally calculated from end-systolic and end-diastolic volumes, may therefore be inaccurate by at least 10% because ventricular volume immediately before mitral valve opening is not utilized in the calculation. Some of the discrepancies between angiocardiographic stroke volume and ejection fraction measurements and those obtained by other methods may be explained by failure to use preinflow volume (PIV) in the calculations.