Aortic insufficiency (AI) is a cond

Aortic insufficiency (AI) is a condition in which the aortic valve fails to close completely at the end of systolic ejection, causing leakage of blood back through the valve during LV diastole.

The constant backflow of blood through the leaky aortic valve implies that there is no true phase of isovolumic relaxation. The LV volume is greatly increased due to the enhanced ventricular filling.

When the LV begins to contract and develop pressure, blood is still entering the LV from the aorta (since aortic pressure is higher than LV pressure), implying that there is no true isovolumic contraction. Once the LV pressure exceeds the aortic diastolic pressure, the LV begins to eject blood into the aorta.

The increased end-diastolic volume (increased preload) activates the Frank–Starling mechanism to increase the force of contraction, LV systolic pressure, and stroke volume.