Adult Echocardiography Practice Exam

Which structure primarily contributes to the resistance in the left ventricular outflow tract in hypertrophic cardiomyopathy?

1. Mitral valve

2. Septum

3. Aortic valve

4. Left atrium

The correct answer is: Septum

In hypertrophic cardiomyopathy (HCM), the primary contributor to the resistance in the left ventricular outflow tract is the interventricular septum. In HCM, this septum may undergo significant hypertrophy, becoming thickened and encroaching into the left ventricular outflow tract. This anatomical alteration leads to a dynamic obstruction to blood flow as the hypertrophied septum interacts with the mitral valve apparatus during systole. As the left ventricle contracts, the flow of blood can be obstructed when the thickened septum moves closer to the anterior mitral valve leaflet. This obstruction can result in increased pressure gradients and can manifest clinically as symptoms of heart failure, syncope, or even sudden cardiac death in some patients. Understanding the mechanics of this condition highlights the importance of the septum's role in HCM, which fundamentally alters the way blood is ejected from the heart. Other structures like the mitral valve, aortic valve, and left atrium, while they can play roles in the overall function of the heart, are not the primary contributors to the outflow tract resistance seen in HCM. The notable pressure gradients and flow dynamics associated with the hypertrophied septum are central to the pathology