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).
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