Metabolic disorders can lead to DCM. A relatively common example is
hemochromatosis, a disease of iron metabolism, which is often familial and more common in men, in whom iron is deposited in the liver and heart muscle.
Peripartum cardiomyopathy is a form of DCM that typically occurs during the last 3 months of pregnancy and up to 6 months after delivery. It occurs in about 1 in every 5,000 pregnancies. The incidence is higher in women older than 30 years old and those with high blood pressure, multiple previous pregnancies, and twin pregnancies. Note that those who experience this condition are strongly discouraged from subsequent pregnancies, as the recurrence rate is high and death can even occur due to heart failure.
Chemotherapy drugs can lead to DCM in some individuals.
Drugs most commonly associated with DCM are doxorubicin, cyclophosphamide, amsacrine, and interferon.
Neuromuscular disorders (disorders of the muscles and nervous system) are also associated with DCM.
Does therapy for DCM differ from that for congestive heart failure due to coronary artery disease (narrowing of the heart arteries)?
Treatment is similar for heart failure due to either DCM or coronary artery disease and includes:
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Salt restriction and diuretics (drugs that reduce lung and leg fluid via increased urine output)
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Beta-blockers (drugs that slow the heart rate and take stress off the heart)
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Angiotensin-converting enzyme (ACE) inhibitors (drugs that reduce the load on the heart by relaxing the body's major blood vessels)
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A combination of hydralazine and isosorbide nitrates (a drug option in those who cannot tolerate ACE inhibitors due to kidney function problems)
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Digoxin (a drug that helps improve the squeezing power of the heart).
What is hypertrophic cardiomyopathy (HCM)?
Hypertrophic cardiomyopathy (HCM) is a primary disorder of the heart muscle characterized by inappropriate hypertrophy (excessive growth) of the left ventricle, which is the chamber that pumps blood to the body's organs and tissues. In many individuals, hypertrophy predominantly involves the septum, which is the intracardiac wall that separates the left ventricle and right ventricle.
In at least one-quarter of cases, this variant leads to obstruction of blood flow out of the left ventricle and into the aorta and, hence, is called hypertrophic obstructive cardiomyopathy (HOCM). Overall annual death rates in HCM individuals are approximately 3% per year in adults, while the rates are higher in those with HOCM.
What are the causes of hypertrophic cardiomyopathy (HCM)?
In more than 50% of cases, HCM is genetically transmitted.
Most experts think that some if not all of the sporadic forms of HCM are due to spontaneous mutations (a sudden change in the genetic code of the developing fetus). At least 8 different genes have been associated with HCM. Note that genetic testing is not currently indicated (except in research settings), even in families in which HCM occurs, because knowing the type of gene defect does not impact subsequent treatment.
What are the most frequent symptoms in patients with HCM?
Shortness of breath (dyspnea) occurs in approximately 90% of symptomatic individuals with HCM. It occurs due to a combination of abnormalities, including poor relaxation of the stiff, thickened heart muscle (diastolic dysfunction), reduced blood flow into the main heart pumping chamber (impaired ventricular filling), and increased pressures in the left atrium and pulmonary veins.
Fainting and near-fainting (syncope and near-syncope) can occur in HCM patients due to inadequate cardiac output during times of increased demand (such as physical exertion or severe stress). Serious arrhythmias can also result in fainting episodes; in fact, such arrhythmias are a top cause of sudden death in otherwise healthy children and young adults.
Chest pain (angina pectoris) occurs in up to three-fourths of symptomatic patients.The discomfort is a result of an imbalance between a reduced oxygen supply to the heart (because of thickened and narrowed heart arteries) and increased demand (due to greater heart muscle).
What noninvasive testing can be used to evaluate patients with suspected DCM or HCM?
Useful tests include electrocardiography (ECG), chest x-ray, and ultrasound (echocardiography).
In symptomatic individuals, the ECG is usually abnormal, but no specific findings are diagnostic of either DCM or HCM.
A chest x-ray will demonstrate an enlarged cardiac silhouette in DCM patients and in some HCM patients.
An echocardiogram provides the most useful and specific information. In DCM patients, severe dilatation of the ventricles is demonstrated, and an accurate estimation can be made of the impairment of heart function. In HCM patients, thickening of the left ventricle is the cardinal feature. Other findings include narrowing of the outflow tract through which blood flows from the left ventricle and out through the aortic valve and into the aorta, a small left ventricular cavity size, and abnormal motion of the mitral valve.
