What is the cause of mid systolic closure of the aortic valve in hypertrophic cardiomyopathy?

Mid-systolic closure of the aortic valve in hypertrophic cardiomyopathy is primarily caused by systolic anterior motion (SAM) of the mitral valve. In this condition, the abnormal positioning and function of the mitral valve, typically resulting from ventricular hypertrophy, can lead to it being pulled toward the outflow tract of the left ventricle during systole. As the mitral valve leaflets move anteriorly, they can obstruct the left ventricular outflow tract and create a turbulent flow pattern. This obstruction can prevent the aortic valve from remaining fully open throughout systole, leading to its mid-systolic closure.

Systolic anterior motion and its relation to the dynamics of blood flow during systole are crucial in understanding the physiological changes that occur in hypertrophic cardiomyopathy. The closing of the aortic valve during mid-systole can also contribute to the characteristic heart murmurs associated with this condition, highlighting the interplay between the mitral and aortic valves under the influence of altered ventricular geometries.