In hypertrophic cardiomyopathy (HCM), there is decreased compliance due to the disorientation of myosin fibres.

Maneouvres which decrease venous return will increase the intensity of the murmur

(valsalva – baroreceptor mediated fall in cardiac output, standing, nitrates).

Maneouvres which increase venous return will decrease the murmur as this overcomes the obstruction (squatting, beta blockers).

Beta blockers and calcium channel blockers help increase end diastolic filling and treat symptoms but have no effect on risk reduction of sudden death. Amiodarone improves survival.

Over a hundred different mutations in at least nine different genes, all encoding sarcomeric polypeptides, have been associated with hypertrophic cardiomyopathy (HCM).