Which physical maneuver during examination typically decreases the intensity of the murmur in hypertrophic obstructive cardiomyopathy?

In hypertrophic obstructive cardiomyopathy (HOCM), the intensity of the outflow tract obstruction can change based on body position and maneuvers during examination. Squatting typically increases venous return to the heart, which in turn increases preload. This leads to dilation of the left ventricle, reducing the obstruction at the left ventricular outflow tract and ultimately decreasing the intensity of the murmur associated with HOCM.

By squatting, the increased blood volume and enhanced filling of the heart helps mitigate the dynamic obstruction caused by the thickened interventricular septum and the mitral valve apparatus being pulled into the outflow tract. As a result, the murmur typically associated with HOCM becomes softer or may even resolve completely due to this hemodynamic change.

Understanding why squatting is effective in this context helps in differentiating HOCM from other cardiac conditions and underscores the importance of maneuvers in clinical assessment.