Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HOCM) has an incidence
of about 1 in 1000. Presentation is with hypertrophy of the left
and/or right ventricle without dilatation. Many affected
individuals are asymptomatic and the initial presentation may
be with sudden death. In others, there is slow progression of
symptoms that include dyspnoea, chest pain and syncope.
Myocardial hypertrophy may not be present before the
adolescence growth spurt in children at risk, but a normal
two-dimensional echocardiogram in young adults will virtually
exclude the diagnosis. Many adults are asymptomatic and are
diagnosed during family screening. Atrial or ventricular
arrhythmias may be asymptomatic, but their presence indicates
an increased likelihood of sudden death. Linkage analysis and
positional cloning has identified several loci for HOCM.
The genes known to be involved include those encoding for
beta myosin heavy chain, cardiac troponin T, alpha
tropomyosin and myosin binding protein C. These are
sarcomeric proteins known to be essential for cardiac muscle
contraction. Mutation analysis is not routine, but mutation
detection allows presymptomatic predictive testing in family
members at risk, identifying those relatives who require
follow up.