The murmur of hyperopic obstructive cardiomyopathy is decreased in which of the following

Ref: Harrison's 19th E pg 1568 In supine position, there is increased venous return. Here blood acts as a physical barrier between hyperophied septum and anterior mitral leaflet. So increased blood in LV, decreases the murmur. Note: Vasodilation, increases the pressure gradient between LV and Aoa and hence increase the murmur. Note :All murmurs decreases with valsalva maneuver except that of HOCM and MVP. In hocm, blood acts as a physical barrier between hyperophied septum and anterior mitral leaflet. During valsalva, there is decreased venous return and subsequently decreased blood reaching LV. As blood flow reduces, there is more chances of obstruction, it increases the murmur (ejection systolic murmur)