Which condition will intensify a hypertrophic cardiomyopathy (HCM) murmur?

In hypertrophic cardiomyopathy (HCM), the murmur typically arises from the outflow obstruction created by the abnormal thickening of the heart muscle, primarily involving the interventricular septum. This murmur is typically a systolic ejection murmur best heard at the left sternal border.

When preload is decreased, such as with dehydration or using certain medications like nitroglycerin, there is a reduction in the volume of blood filling the heart. This decrease in preload leads to a lesser degree of ventricular filling and can result in increased obstruction of blood flow out of the left ventricle during systole. As the ventricle contracts against this obstruction with less blood volume, the turbulence of the flow increases, leading to a more pronounced murmur.

Understanding how changes in preload can affect the hemodynamics and the resultant sound characteristics of the HCM murmur is essential for clinical evaluation. Thus, decreased preload serves to intensify the murmur associated with hypertrophic cardiomyopathy, making it an important consideration in the assessment and management of the condition.