Myocardial Disorders in the Neonate Manish Bansal, MD* *Division of Pediatric Cardiology, University of Iowa Stead Family Children’s Hospital, Iowa City, IA Education Gaps 1. Several physiologic changes take place in the myocardium after birth. 2. Knowledge about common primary myocardial disorders that present in the neonatal period has been limited. Abstract Myocardial disorders in the neonate could be a signi ficant cause of morbidity and mortality. The neonatal myocardium is immature and undergoes several changes after birth. These include changes in the size of the myocardium, cellular transport of calcium, and utilization for fatty acid and glucose metabolism. Neonatal myocardium relies heavily on the heart rate to improve cardiac output. Myocardial disorders in the neonate can be classi fied as primary and secondary. Primary myocardial disorders have an inherent abnormality in the cardiac muscle and can be further subclassi fied based on the morphology and presentation. These include hypertrophic cardiomyopathy, dilated cardiomyopathy, and restrictive cardiomyopathy. Secondary myocardial disorders are usually caused by a systemic disorder that affects the cardiac muscle and function. These include inborn errors of metabolism, neuromuscular disorders, and mitochondrial disorders. The diagnosis and management of cardiomyopathy is very speci fic to the type of cardiomyopathy or underlying disorders. A team approach, including neonatology, genetics and metabolism, and cardiology and cardiac transplantation, is essential in managing these cases. Objectives After completing this article, readers should be able to: 1. Describe myocardial physiology and adaptation in the neonatal period. 2. List the common primary myocardial disorders. 3. Recognize myocardial disorders secondary to other diseases. AUTHOR DISCLOSURE Dr Bansal has disclosed no financial relationships relevant to this article. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device. ABBREVIATIONS ARVC arrhythmogenic right ventricular cardiomyopathy DCM dilated cardiomyopathy ECG electrocardiography HCM hypertrophic cardiomyopathy IEM inborn error of metabolism LVOT left ventricular outflow tract MRI magnetic resonance imaging Vol. 19 No. 7 JULY 2018 e403 at Preeyaporn Rerkpinay on July 10, 2018 http://neoreviews.aappublications.org/ Downloaded from
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Myocardial Disorders in the Neonate...the adult: to increase heart rate and/or inotropy to improve cardiac output. At birth, neonatal myocardial tissue responds to changes in the circulation
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Myocardial Disorders in the NeonateManish Bansal, MD*
*Division of Pediatric Cardiology, University of Iowa Stead Family Children’s Hospital, Iowa City, IA
Education Gaps
1. Several physiologic changes take place in the myocardium after birth.
2. Knowledge about common primary myocardial disorders that present in
the neonatal period has been limited.
Abstract
Myocardial disorders in the neonate could be a significant cause of
morbidity and mortality. The neonatal myocardium is immature and
undergoes several changes after birth. These include changes in the size
of the myocardium, cellular transport of calcium, and utilization for fatty
acid and glucose metabolism. Neonatal myocardium relies heavily on
the heart rate to improve cardiac output. Myocardial disorders in the
neonate can be classified as primary and secondary. Primary myocardial
disorders have an inherent abnormality in the cardiac muscle and can be
further subclassified based on the morphology and presentation. These
include hypertrophic cardiomyopathy, dilated cardiomyopathy, and
restrictive cardiomyopathy. Secondary myocardial disorders are usually
caused by a systemic disorder that affects the cardiac muscle and
function. These include inborn errors of metabolism, neuromuscular
disorders, and mitochondrial disorders. The diagnosis and management
of cardiomyopathy is very specific to the type of cardiomyopathy or
underlying disorders. A team approach, including neonatology, genetics
and metabolism, and cardiology and cardiac transplantation, is essential
in managing these cases.
Objectives After completing this article, readers should be able to:
1. Describe myocardial physiology and adaptation in the neonatal period.
2. List the common primary myocardial disorders.
3. Recognize myocardial disorders secondary to other diseases.
AUTHOR DISCLOSURE Dr Bansal hasdisclosed no financial relationships relevant tothis article. This commentary does not containa discussion of an unapproved/investigativeuse of a commercial product/device.
ABBREVIATIONS
ARVC arrhythmogenic right ventricular
cardiomyopathy
DCM dilated cardiomyopathy
ECG electrocardiography
HCM hypertrophic cardiomyopathy
IEM inborn error of metabolism
LVOT left ventricular outflow tract
MRI magnetic resonance imaging
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arrest in normal cardiac embryogenesis. (13) Left ventricle
noncompaction cardiomyopathy may be an isolated abnor-
mality or associated with other congenital heart diseases
such as LVOT abnormalities, Ebstein anomaly, and tetral-
ogy of Fallot. (14) The diagnosis is usually made with
2-dimensional echocardiography or cardiac MRI. Presenta-
tion in the neonatal period is usually associated with poor
prognosis, leading to death or a need for transplantation
early in life.
Conduction System Diseases. As depicted in the Table,
there are various conduction system abnormalities and ion
channel disorders that are classified as cardiomyopathies.
Although classified in this way, the myocardium is usually
normal in these disorders. These disorders are character-
ized by ECG changes and arrhythmias. Cardiac function
could be affected secondary to an arrhythmia. Several spe-
cific genes have been connected to these disorders.
MixedDilated Cardiomyopathy. Dilated cardiomyopathy (DCM) is
more common than HCM or restrictive cardiomyopathy.
(15) The prevalence is about 1 in 2,500 in the general
population and it is the most frequent cause of heart trans-
plantation. DCM can result from a primary abnormality
in the cardiac myocyte or can be secondary to a wide range
of other disorders such as myocarditis. Other secondary
causes include autoimmune and systemic disorders, pheo-
chromocytoma, neuromuscular disorders, and mitochon-
drial, endocrine, and nutritional disorders. About 20% to
35% of DCM cases are familial. (8) Inheritance is hetero-
geneous, with most cases being autosomal dominant.
Patients with DCM usually present at a later age and
rarely in the neonatal period. This disorder is characterized
by ventricular enlargement and decreased systolic function;
affected patients present with symptoms of low cardiac
output such as pallor, irritability, and diaphoresis. (7) Phys-
ical findings include tachypnea, tachycardia, narrow pulse
pressure, and hepatomegaly. ECG shows flattening of the T
wave with possible depression of the ST segments. Cardio-
megaly is evident on chest radiography. Echocardiography is
diagnostic. Cardiac MRI is often helpful in identifying
myocardial fibrosis and scarring but may be difficult to
interpret in neonates with increased heart rates. Manage-
ment includes treatment of heart failure. In contrast to
HCM, vasodilators, diuretics, and inotropes are useful in
the management of DCM. If management is unsuccessful,
patients can develop severe heart failure, arrhythmias, or
sudden death.
Restrictive Cardiomyopathy. This is an extremely rare
condition in which the ventricular cavities are small and
diastolic function is impaired, involving both but predom-
inantly the left ventricle. (7) The systolic function is normal,
at least initially. It is very rare in neonates. Affected neonates
present with signs and symptoms of congestive heart fail-
ure. ECG often shows conduction abnormalities and evi-
dence of ischemia at higher heart rates. Echocardiography
shows normal or small ventricles with dilation of both atria.
Restrictive cardiomyopathy should be differentiated from
constrictive pericarditis as affected patients could have
Figure 3. Echocardiogram of a neonate with left ventriclenoncompaction cardiomyopathy. Arrow shows the deep trabecularrecess.
Figure 2. Echocardiogram of a neonate showing left ventricularhypertrophy with more pronounced septal hypertrophy. LV¼leftventricle; RV¼right ventricle.
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presenting symptom. (30) Duchenne and Becker muscu-
lar dystrophies are among the most common myopathies
associated with cardiomyopathy. The heart is usually
affected later in life and affected infants usually are
asymptomatic.
Myotonic dystrophy is the most common form of mus-
cular dystrophy. The clinical presentation depends on the
form of the disease: congenital, infantile, juvenile, or adult-
onset. The severity depends on the number of CTG repeats,
with the most severe disease developing in patients with
more than 1,000 repeats. (30) The congenital form presents
with decreased movements in fetal life, hypotonia, and
respiratory failure. Cardiac involvement appears in the
second decade of life. Cardiovascular symptoms in these
disorders are not overt because of the low level of physical
activity.
Mitochondrial DisordersMitochondrial disorders are a heterogeneous group of
multisystem diseases secondary to mutations in nuclear
or mitochondrial DNA. These can be diagnosed at any age
depending on the severity of the disease. Cardiac manifes-
tations could include HCM or DCM. (31) Cardiac involve-
ment is typical of certain abnormalities.
Kearns-Sayre syndrome is a mitochondrial myopathy
consisting of ptosis, ophthalmoplegia, and retinal pigmen-
tation; affected patients are predisposed to atrioventricular
conduction abnormalities.
Patients with myoclonic epilepsy with ragged red
fibers or mitochondrial encephalomyopathy with lactic
acidosis and strokelike episodes could develop HCM or
DCM.
The most common infantile mitochondrial disorder is
Leigh syndrome, a progressive neurodegenerative disorder.
(31) This syndrome is characterized by gliosis, demyelin-
ation, capillary necrosis, and necrosis in the brain. Cardiac
involvement could be in the form of HCM and conduction
defects such as Wolff-Parkinson-White syndrome.
Sengers syndrome presents with congenital cataracts,
HCM,mitochondrialmyopathy, and lactic acidosis. Affected
patients can present with a severe neonatal form that causes
infantile death or a more benign form with longer survival.
The cause of death is usually HCM.
Barth syndrome is an X-linked genetic disorder charac-
terized by cardiomyopathy, intermittent neutropenia, mus-
cular weakness, and 3-methyl-glutanic aciduria. It is caused
by mutation in the tafazzin (TAZ) gene. Affected patients
have a high mortality rate during infancy as a result of
cardiac dysfunction.
DIAGNOSIS AND MANAGEMENT
The evaluation of patients with a cardiomyopathy ismethod-
ical, and involves evaluation by multiple specialties includ-
ing neonatology, cardiology, metabolism, and genetics.
Psychological and family support should be available,
because quite often these patients have an underlying
systemic or genetic disorder that requires extensive coun-
seling and guidance. The cardiac transplant team should
be involved when providers suspect a possible cardiomyop-
athy. If relevant, a muscle or myocardial biopsy can help to
identify the underlying neuromuscular disorder. Manage-
ment of secondary cardiomyopathies often involves correc-
tion of the underlying metabolic or genetic disorders. The
role of immunoglobulin administration in neonatal myo-
carditis is uncertain. Cardiac failure is oftenmanaged symp-
tomatically with the use of diuretics, afterload-reducing
agents in infants with DCM, and b-blockers in patients
with HCM.
CONCLUSION
Myocardial disorders in the neonatal period are not uncom-
mon and may have a heterogeneous presentation. Patients
with a primary cardiomyopathy usually do not present
during the neonatal period. If symptoms are present, the
condition is usually associated with a poor prognosis.
Patients with a secondary cardiomyopathy may present in
the neonatal period, depending on the severity of the
underlying defect.
American Board of PediatricsNeonatal-Perinatal ContentSpecifications• Know the anatomy and pathophysiology (including genetics) ofan infant with a condition affecting myocardial performance.
• Recognize the clinical features in an infant with a conditionaffecting myocardial performance.
• Recognize the laboratory, imaging, and other diagnostic featuresof an infant with a condition affecting myocardialperformance.
• Formulate a differential diagnosis of an infant with a conditionaffecting myocardial performance.
• Know the evaluation and medical and/or surgical managementand associated potential complications or adverse effects of suchmanagement for an infant with a condition affecting myocardialperformance.
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