What murmur characteristic is most associated with idiopathic hypertrophic obstructive cardiomyopathy?

In idiopathic hypertrophic obstructive cardiomyopathy (IHOCM), the primary feature is the obstruction of left ventricular outflow, which often occurs during systole. This condition leads to a characteristic systolic murmur that is typically described as increasing in intensity with maneuvers that decrease venous return, such as when a patient stands or performs the Valsalva maneuver. This occurs because reducing the venous return causes less blood in the left ventricle, which exaggerates the outflow tract obstruction and consequently intensifies the murmur.

This characteristic response to changes in venous return is crucial in distinguishing IHOCM from other cardiac conditions. In IHOCM, the murmur is also often described as a "crescendo" type during systole, but the emphasis on how it intensifies with decreased venous return helps in confirming the diagnosis. Understanding this connection between the murmur and the hemodynamic changes due to venous return is essential for recognizing IHOCM in clinical practice.