The murmur of HOCM is important to detect due to its clinical implications. The murmur is high-pitched, crescendo-decrescendo, midsystolic murmur heard best at the left lower sternal border.  The murmur of HOCM does not radiate to the carotids like that of AS.  The important auscultatory features of HOCM that distinguish it from AS relate to dynamic auscultation.

The murmur of HOCM becomes quite loud with Valsalva. This maneuver effectively acts to decrease left ventricular filling which results in worsened left ventricular outflow tract obstruction in patients with HOCM making the murmur louder. Standing from the squatting position has a similar effect (this results in sudden pooling of blood in the legs decreasing venous return). In patients with aortic valvular stenosis, the murmur will get softer with Valsalva/standing since less blood is being ejected through the aortic valve. Rapid squatting from a standing position forces increased venous return and would have the opposite effect of Valsalva/rapid standing.

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