Murmur increasing with Valsalva manouvre -

Increases 65% of the time with hyperophic cardiomyopathy; decreased 30% of the time; Increased intensity 65% sensitive and 96% specific for hyperophic cardiomyopathy as opposed to other lesions Most other murmurs decreased intensity during Valsalva. Physiologic explanation: murmur intensity increases with decreased LV volume because of increased proximity of septum and mitral valve; decreased venous return with Valsalva Ref Harrison 20th edition pg 1446