Hypertrophic cardiomyopathy is a primary myocardial disorder of unknow
n cause with diverse clinical manifestations due to unimpaired, someti
mes hyperkinetic, systolic left ventricular ejection function with or
without outflow tract obstruction and/or diastolic dysfunction from im
paired ventricular relaxation. Autosomal dominant genetic transmission
is common, with sporadic occurrence in, at most, half of the cases. M
olecular genetic analysis demonstrates abnormal myosin heavy-chain gen
e expression in some families. Asymmetrical left ventricular hypertrop
hy occurs with disproportional thickening of the anterior basal septum
compared with the free wall. Extensive and widespread myocardial fibe
r disarray is common. A systolic pressure gradient across the left ven
tricular outflow tract may be present at rest, can be induced as with
isoproterenol, or may be absent. The clinical picture and prognosis ar
e greatly affected by the common diastolic dysfunction of impaired ven
tricular relaxation due to increased stiffness. Although hypertrophic
cardiomyopathy may be recognized in infancy, clinical signs usually be
gin in adolescence or young adult years. Presenting symptoms are dyspn
ea, fatigue, chest pain, syncope, or sudden death. Infants may present
for evaluation because of a family history, the auscultation of an as
ymptomatic murmur, or, less frequently, because of an arrhythmia or co
ngestive heart failure. The echocardiogram is the most useful tool for
monitoring the evolution of the disease and results of treatment. Sig
nificant diagnostic features are left ventricular hypertrophy, asymmet
ric septal hypertrophy, and systolic anterior motion of the anterior m
itral leaflet. Doppler echocardiographic studies can quantify the degr
ee of outflow tract obstruction and are useful to evaluate therapy. In
dices of diastolic left ventricular dysfunction are demonstrable, incl
uding wall motion abnormalities, prolongation of early diastolic peak
velocity of flow across the mitral valve, flow deceleration and relaxa
tion times, and a decreased mitral E:A flow ratio. Hemodynamic evaluat
ion by cardiac catheterization is used less often today because of the
usefulness of echocardiagraphic studies. Holter 24- to 48-hour electr
ocardiographic monitoring is advised to identify patients with ventric
ular tachycardia who have a risk of sudden and unexpected death. In al
l age-groups, however, and especially in children, the absence of vent
ricular arrhythmia in no way excludes the possibility of sudden death.
Beta-Adrenergic blocking medications have been the primary medical tr
eatment for hypertrophic cardiomyopathy for many years, but these agen
ts do not appear to change the natural history of the condition or pre
vent sudden death. Verapamil, the most widely used calcium channel blo
cker in hypertrophic cardiomyopathy, appears to improve symptoms and e
xercise capacity. Amiodarone, which suppresses ventricular tachycardia
, may prevent sudden death. Surgical therapy for hypertrophic cardiomy
opathy is considered elsewhere in this issue of Progress in Pediatric
Cardiology.