Question

How will blood leaking through an incompetent aortic valve during diastole affect the preload and stroke volume of the left ventricle?

Answer 1

Valvular insufficiency results from valve leaflets not completely sealing when a valve is closed is called as aortic regurgitation. Aortic regurgitation occurs when the aortic valve fails to close completely and blood flows back from the aorta (Ao) into the left ventricle after ejection into the aorta is complete and during the time that the left ventricle (LV) is also being filled from the left atrium (LA). Because the ventricle is being filled from two sources (aorta and LA), this leads to much greater LV filling; therefore, LV end-diastolic volume is increased as well as LV end-diastolic pressure. The increased ventricular end-diastolic volume (preload) leads to an increase in the force of contraction through the Frank-Starling mechanism, which causes a greater than normal stroke volume into the aorta. This elevates aortic systolic pressure ; however, the aortic diastolic pressure is much lower than normal because blood more rapidly leaves the aorta due to regurgitation back into the ventricle. Therefore, a defining characteristic of aortic regurgitation is an increase in aortic pulse pressure (systolic minus diastolic pressure). The elevation in LV end-diastolic pressure causes blood to back up into the left atrium and pulmonary veins, which leads to an increase in left atrial pressure and pulmonary capillary wedge pressure, which can result in pulmonary congestion and edema. The backward flow of blood into the ventricular chamber during diastole results in a diastolic murmur.