Congenital malformations - Edocr

Chapter 32
Cardiomyopathy
BARBARA K. BURTON
INTRODUCTION
Cardiomyopathy is a disorder that results fundamentally
from a defect in the cardiac myocyte
in the absence of a gross anatomic anomaly of
the heart. Dilated cardiomyopathy is characterized
by diminished cardiac contractility with ventricular
enlargement, abnormal diastolic function
and congestive heart failure. In contrast, hypertrophic
cardiomyopathy is characterized by inappropriate
thickening of the ventricular walls with
normal, hyperdynamic, or decreased systolic
performance and normal or decreased ventricular
chamber size.
EPIDEMIOLOGY/ETIOLOGY
The etiology of cardiomyopathy is extraordinarily
diverse, particularly in the neonate. Many different
insults, including infection, asphyxia, or exposure
to toxic metabolites may result in myocyte
injury with subsequent myocardial dysfunction. 1
The estimated incidence of cardiomyopathy from
all causes, in the absence of structural heart disease,
is approximately 1 in 10, 000 births. Among
the infectious causes known to be associated
with neonatal dilated cardiomyopathy are bacterial
sepsis and viral myocarditis associated with
agents such as echovirus and Coxsackie virus, type
B. Many inherited metabolic disorders are associated
with dilated cardiomyopathy. Some may
present acutely with other systemic findings that
give clues to the diagnosis while in other cases,
cardiomyopathy may be the sole presenting manifestation.
Disorders associated with congenital lactic
acidosis, such as mitochondrial respiratory chain
defects or defects in pyruvate metabolism, are
often associated with cardiomyopathy, which
may be either dilated or hypertrophic. When elevated
plasma lactic acid levels are noted in an
infant with severe cardiomyopathy and signs of
congestive heart failure, there may be difficulty in
determining whether the lactic acidosis is a primary
finding or secondary to decreased peripheral
perfusion. Sequential determinations following
initiation of treatment may be helpful in sorting
this out. In addition, measurement of lactic acid in
cerebrospinal fluid or in brain by magnetic resonance
spectroscopy is often abnormal in infants
with defects in the respiratory chain or in pyruvate
metabolism, and can be helpful diagnostically.
Patients with Barth syndrome characteristically
exhibit a finding of ventricular noncompaction
on echocardiogram in addition to dilated cardiomyopathy,
neutropenia, and 3-methyglutaconic
aciduria. They have a mutation in the X-linked
gene that codes for the protein tafazzin. Mutations
in the tafazzin gene may also give rise to variant
phenotypes including X-linked cardiomyopathy
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