Table of Contents
Definition and Classification of Cardiomyopathy
Cardio = heart
Myo = muscle
Pathy = disease
As the name indicates, cardiomyopathy refers to a group of myocardial diseases. This group of diseases is associated with impaired systolic and diastolic function.
The two types of cardiomyopathy
- The primary type of cardiomyopathy consists of heart muscle diseases predominantly involving the myocardium and having an unknown etiology. The following are primary types of cardiomyopathy:
- Genetic: hypertrophic myopathies, arrhythmogenic right ventricular dysplasia, glycogen storage disorders, mitochondrial myopathies
- Acquired: inflammatory cardiomyopathies (myocarditis), peripartum cardiomyopathies, tachycardia-induced cardiomyopathies
- Mixed: idiopathic dilated cardiomyopathies, restrictive cardiomyopathies
- The secondary type consists of myocardial disease of a known cause or associated with a systemic disease (e.g., amyloidosis) or chronic alcohol use. These include the following:
- Infiltrative cardiomyopathies, including amyloidosis
- Storage cardiomyopathies, including hemochromatosis
- Toxicity cardiomyopathies induced by drugs, e.g., chemotherapeutic agents
- Inflammatory cardiomyopathies, including sarcoidosis
- Endocrine cardiomyopathies, including hypothyroidism or hyperthyroidism and diabetes
- Neuromuscular/neurologic myopathies
- Autoimmune myopathies, including systemic lupus erythematosus, rheumatoid arthritis, and scleroderma
The World Health Organization (WHO) classifies five types of cardiomyopathy on the basis of cardiac changes, as follows:
- Dilated cardiomyopathies (DCMs)
- Hypertrophic nonobstructive cardiomyopathy (HNCM) or hypertrophic obstructive cardiomyopathy (HOCM)
- Restrictive cardiomyopathies (RCMs)
- Arrhythmogenic right ventricular cardiomyopathies (ARVCs)
- Unclassified cardiomyopathies
Potential complications of cardiomyopathy include heart failure, arrhythmias, and sudden death. It is the second most common cause of sudden death (ischemic heart disease is the most common). In the past, few cardiomyopathies were thought to be genetic in origin; currently, at least one-third of cardiomyopathies are known to be genetic. The prognosis for dilated cardiomyopathy is poor, especially if the condition is diagnosed late in its course, when heart failure signs and symptoms are already present.
DCM is the most common type of nonischemic cardiomyopathy; it has an incidence of 6 in 100,000 population and affects men more often than women. The cause is usually unknown; however, DCM is easily identified on the basis of an enlarged left ventricular diameter, which is observed using echocardiography, and the rarefaction of cardiomyocytes observed during microscopic examination. DCM can be inherited or may be a result of underlying conditions. Diseases such as diabetes, viral heart infection, thyroid disease, and abnormalities in the valves of the heart may lead to DCM. The postpartum cardiomyopathy that occurs in women is associated with a sudden change in cardiovascular function and blood volume, though the exact cause is not known.
Patients who have symptoms of heart insufficiency—i.e. dyspnea, lung edema (left ventricular insufficiency), or blood stasis in the peripheral body (right ventricular insufficiency)–should be observed for the likelihood of DCM. Other symptoms include pitting edema, weight gain, dizziness, fainting, and shortness of breath.
Electrocardiography (ECG), blood tests, X-ray examination, magnetic resonance imaging (MRI), myocardial biopsy, computed tomography (CT) scans, and cardiac catheterization are some tests that may help in the diagnosis of DCM.
DCM is treated (according to heart insufficiency) using diuretics, vasodilators, angiotensin-converting enzyme (ACE) inhibitors, and beta blockers, which delay the progression of the disease and lower the risk of sudden cardiac death. Such treatment also aims to improve cardiac function, as well as alleviate most of the symptoms. Lifestyle changes are usually necessary, including adding exercise and changing the diet, in order to improve treatment outcomes. In addition, if arrhythmic side effects occur, implantation of a cardiac resynchronization system is indicated. If the left ventricular ejection fraction (LVEF) falls below 35% during the course of treatment, oral anticoagulation using vitamin K antagonists such as warfarin and placement of an implantable cardiodefibrillator (ICD) is necessary. Note, however, that some patients are asymptomatic.
Hypertrophic cardiomyopathy is treated (according to heart insufficiency) using diuretics, vasodilators, ACE inhibitors, and beta blockers, which delay progression of the disease and lower the risk of sudden cardiac death. Such treatment also aims to improve cardiac function, as well as alleviate most of the symptoms. Lifestyle changes are usually necessary, including adding exercise and changing the diet, in order to improve treatment outcomes. In addition, if arrhythmic side effects occur, implantation of a cardiac resynchronization system is indicated. If the LVEF falls below 35% during the course of treatment, oral anticoagulation using vitamin K antagonists such as warfarin and placement of an ICD is necessary. Note, however, that some patients are asymptomatic.
Hypertrophic cardiomyopathy can be diagnosed using two-dimensional echocardiography, chest radiography, radionuclide imaging, or cardiac MRI.
Treatment of hypertrophic cardiomyopathy
- Beta blockers, verapamil (a calcium channel blocker), disopyramide, and amiodarone have been found to be useful to treat symptoms.
- Beta blockers in high doses are the first-line therapy.
- No pharmacologic treatment is known to improve prognosis.
- Atrial and ventricular arrhythmias are common and often respond to antiarrhythmic drug therapy, including beta blockade.
- Outflow tract obstruction can be improved by the following:
- Partial surgical resection (myectomy)
- Iatrogenic infarction of basal septum (septal ablation with alcohol)
- Placement of an ICD for patients at risk for sudden death
Among the approaches for the treatment of DCM are septal myectomy (Morrow myectomy) and a transcoronary ablation of septal hypertrophy (TASH) procedure. The latter procedure detects the arterial branch that feeds the bulge, into which alcohol is injected in order to devitalize the muscular mass.
Although RCM is fairly uncommon in Western countries, it is commonly observed in tropical regions. In contrast to DCM, RCM is a diastolic malfunction caused by increased rigidity (i.e. reduced compliance) of the heart’s wall due to a buildup of connective tissue, leading to increased pressure in the atria and the ventricles. RCM can also have a genetic cause, and it has been shown to be curable using molecules that silence the genes responsible for abnormal protein production.
RCM is difficult to recognize on echocardiography, though there are clinical symptoms of heart insufficiency that serve as the basis for diagnosis.
Common causes of RCM are infiltrations of the myocardium, storage diseases, and endocarditis and myocarditis. Here, Loeffler endocarditis is to be named to a special degree, which leaves scars that lead to rigidity. In this case, cortisone must be added to conventional medicinal therapy. Moreover, surgical excision of the endocardium is required. Corticosteroids are used to treat sarcoidosis, Loeffler endocarditis chemotherapy is used to treat amyloidosis, and endarterectomy is used to treat endomyocardial fibrosis and Loeffler endocarditis.
|Diagnosis is often difficult because of the following:
Arrhythmogenic Right Ventricular Cardiomyopathy
The most uncommon type of cardiomyopathy is ARVC, which is a heritable type of cardiomyopathy associated with ventricular arrhythmia and tachycardia. ARVC can lead to sudden cardiac death.
Therapy includes antiarrhythmic drugs, ICD placement, and catheter ablation. Physical stress must be avoided. Patients with ARVC and a family history of the disease require changes in lifestyle, as well as regular testing.
It is important to understand the fundamental pathomechanisms and types of therapy associated with cardiomyopathies. Details and numbers may lead to a diagnosis, but don’t lose yourself in these details. The morphologic differences between the different types can be memorized quite well by visualization.