• Dilated cardiomyopathy (DCM): Impairment of biventricular systolic function with predominant involvement of the left ventricle eliciting congestive heart failure.
• Hypertrophic cardiomyopathy (HCM): Characterized with an asymmetric hypertrophy of the left ventricle with 20% to 25% of the patients exhibiting left ventricular outflow tract obstruction.
• Restrictive cardiomyopathy (RCM): Cardiac muscle disease that impairs ventricular filling (normal or decreased diastolic volume of the ventricles), yet systolic function generally remains normal.

• DCM: There are many associated diseases that cause DCM, which are grouped as inborn errors of fatty-acid oxidation, disorders of mitochondrial oxidative phosphorylation, X-linked muscular dystrophies, toxin-induced cardiomyopathy (i.e., anthracycline), post-infectious (viral myocarditis associated with coxsackievirus B or echovirus), nutritional deficiencies, primary and secondary carnitine deficiency, and chronic tachyarrhythmias. Similarly, idiopathic DCM is manifested by abnormally dilated ventricular chambers with frequently noted mural thrombi and atrioventricular valve leaflet scarring with secondary annulus dilatation, and hypertrophy and degeneration of myocytes.
• HCM: This disease is manifested by ventricular hypertrophy, which is often asymmetrical and involves the interventricular septum most commonly but may also affect the free walls. Dynamic obstruction of the left ventricular outflow tract can occur and anatomically relates to the presence of mitral valve systolic anterior motion causing subaortic obstruction.
• RCM: Causes of RCM include amyloidosis, infiltrative and storage diseases (Gaucher disease, Hurler syndrome, Fabry disease), carcinoid syndrome, and radiation-induced fibrosis. Idiopathic RCM can also be familial. The disease is manifested by increased stiffness of the myocardium; therefore, small increases in volume will cause a disproportionately greater increase in ventricular pressure.

• DCM: A portion of cases of idiopathic DCM may have a genetic cause with approximately 20% of patients with the disease having a first-degree relative with abnormalities of myocardial function.
• HCM: A familial hypertrophic cardiomyopathy is known and is an autosomal dominant disease with variable penetrance. Other studies have noted areas of chromosome 1, 14, and 15 to be involved, and can document 60% of patients who have a first-degree relative with morphological evidence of HCM.
• RCM: Idiopathic cases may have a familial occurrence and may be associated with a skeletal myopathy. Also, an autosomal dominant form of the disease with variable penetrance has been associated with Noonan syndrome.

• DCM: Idiopathic DCM has a prevalence of 36/100,000. Overall survival of 50% to 60% at 2 years.
• HCM: Prevalence of 1/500 with a heterogeneous natural history of the disease.
• RCM: Least common of the cardiomyopathic disorders.

• In some studies, the overall actuarial survival of those with DCM is 63% to 90% at 1 year with a 5-year survival of 20% to 80%.
• Arrhythmias may be seen and are most often ventricular in origin.
• Thrombus formation can be seen in DCM due to the stasis of blood in a hypocontractile state and, therefore, systemic or pulmonary emboli are possible.

• A general rule for idiopathic DCM is that one-third exhibit improved cardiac function, one-third have stable cardiac dysfunction, and one-third progress to significant cardiac dysfunction.
• Overall rate of sudden death is 2% to 4% in HCM with deaths occurring most commonly in children and young adults.
• The reported median survival in RCM is 1.4 years in children.

• DCM: Children and young adults often present with symptoms that mimic other disease states. For example, abdominal distention, right upper quadrant pain, nausea, and anorexia that indicates right heart failure could be mistaken for hepatic or gallbladder disease. Dyspnea on exertion may mimic exercise-induced asthma. The cardiomegaly on chest radiograph may be mistaken for a large pericardial effusion.
• HCM: This disease must be differentiated from the left ventricular hypertrophy that is seen in an athlete.
• RCM: Must be distinguished from constrictive pericarditis (a history of tuberculosis, trauma, or cardiac surgery may suggest constrictive pericarditis).

Question: Respiratory distress?
Significance: A manifestation of congestive heart failure.

Question: Irritability?
Significance: A manifestation of congestive heart failure on a pericardiol effusion.

Question: Diaphoresis?
Significance: A manifestation of congestive heart failure.

Question: Gastrointestinal complaints (nausea, emesis)?
Significance: Right-sided congestive heart failure; pericardial effusion or decreased systomic output.

Question: Tachypnea with feeding, pallor, and poor weight gain?
Significance: A manifestation of congestive heart failure.

Question: Chest pain?
Significance: Carditis, pericardial effusion, or arrhythemia.

Question: Syncope?
Significance: Low cardiac output or arrhythemia.

Question: Palpitations?
Significance: Arrhythemia.

Question: Orthopnea, paroxysmal nocturnal dyspnea?
Significance: A manifestation of congestive heart failure.

Question: Peripheral edema?
Significance: Right-sided heart failure.

Question: Reduced exercise capacity?
Significance: Congestive heart failure or low cardiac output.

Question: Neurological changes (delayed development)?
Significance: Systemic emboli in DCM.

Question: Recent febrile illness?
Significance: In DCM, 50% of cases have a history of fever within 3 months of the diagnosis.

Finding: DCM: tachycardia, cardiomegaly, hepatomegaly, S3 or S4 gallop
Significance: Evidence of heart failure and decreased cardiac output.

Finding: HCM: Can be normal.
Significance: The presence of outflow tract obstruction produces a systolic ejection murmur of variable intensity related to the degree of obstruction, the murmur increases in intensity with Valsalva and decreases in magnitude with squatting. A parasternal or carotid thrill may be present

Finding: RCM: Jugular venous pulse either fails to fall versus rises in inspiration (Kussmaul sign), S3 or S4
Significance: Advanced cases may exhibit weak peripheral pulses as evidence of low cardiac output.

Finding: Tachypnea, rales, or cardiac wheezing
Significance: Signs of congestive heart failure

Finding: Hepatomegaly, ascites, tenderness to palpation
Significance: Right-sided congestive heart failure.

EXTREMITIES

Finding: Peripheral edema in advanced cases
Significance: Congestive heart failure.

Test: Chest radiograph
Significance: Cardiomegaly, pulmonary edema, Kerley B lines, and pleural effusions

Test: Electrocardiogram
Significance: Non-specific ST-T wave changes, hypertrophy or enlargement of chambers (although generalized low voltages may be seen), ventricular and supraventricular tachyarrhythmias, atrioventricular block, localized Q waves

Test: Echocardiography
Significance: Allows for measurement of systolic function, ventricular dimensions, outflow tract obstruction, and diastolic filling properties.

Test: Cardiac catheterization
Significance: DCM: Low cardiac output with possible alterations in pulmonary vascular resistance, performance of endomyocardial biopsies, aortography to assure usual coronary anatomy (rule out anomalous coronary origin) HCM: Determination of the presence or absence of left ventricular outflow tract obstruction, hypertrophy, “spike and dome” arterial pulse tracing, Brockenbrough phenomenon (a beat following a premature ventricular contraction exhibits an arterial pulse pressure less than that of the control beat) RCM: Atrial pressures are elevated and equal, the ventricular pressure exhibits a rapid and deep early decline at the onset of diastole followed by a rapid rise to a plateau in early diastole (so-called “square-root sign”)

• DCM: Vasodilators (enalapril, hydralazine), anticoagulation to avoid embolic complications, antiarrhythmics as needed, inotropic agents (Digoxin), beta-adrenergic blockers (Metoprolol, Carvedilol), and at the time of diagnosis, a trial of prednisone and/or intravenous gamma globulin.
• HCM: Beta-adrenergic blockers, Verapamil, Nifedipine, Diltiazem, antiarrhythmics as needed. If medical therapy is not effective, other options may include myotomy-myectomy or atrioventricular sequential pacing to relieve outflow tract obstruction.
• RCM: Diuretics can be used with caution to treat venous congestion, antiarrhythmics as needed, anticoagulation to avoid embolic complications, regulated physical activity, and supportive care.
• Patients can be successfully transplanted.

Q: Should family members be evaluated once a cardiomyopathy is diagnosed in a first degree relative?
A: Yes. In some types of cardiomyopathy, there is a strong genetic component and family members should be evaluated. Certainly the diagnosis of certain subtypes of cardiomyopathy (i.e., post-infectious DCM, toxin-induced DCM) do not require evaluation of relatives.

Q: Does the cardiomyopathy of infants of diabetic mothers carry the same clinical course and outcome as that of patients with HCM?
A: No. The pathophysiology initially is similar in that asymmetric hypertrophy of the ventricular septum is often seen in the cardiomyopathy in infants of diabetic mothers and can be obstructive to left ventricular outflow. However, the clinical course of the cardiomyopathy in infants born to diabetic mothers is usually benign and resolves within the first 6 months of life.

Q: What are the differentiating features of HCM and the benign physiological hypertrophy of an athlete’s heart?
A: Several criteria are used to make this distinction. For example, a familial history of HCM leads one to be suspicious of this entity. Studies have suggested specific left ventricular dimensions by echocardiography to differentiate benign hypertrophy and HCM (i.e., a wall thickness of ³15 mm or left ventricle cavity dimensions of <45 mm are more consistent with HCM). Also, echocardiographic evidence of abnormal mitral valve inflow is suggestive of HCM.

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