The cardiomyopathies constitute a diverse group of diseases of both known and unknown etiology characterized by myocardial dysfunction, that is, diseases that are not the result of arteriosclerotic, hypertensive, congenital, or valvular disease.28 Cardiomyopathies can be grouped into three general categories: dilated or congestive, hypertrophic, and restrictive-obliterative. The last category is usually rarely encountered by the forensic pathologist, since it deals with entities such as amyloidosis, hemochromatosis, sarcoidosis, glycogen storage disease, and hypereosinophilic syndrome, conditions not usually associated with sudden death and mostly of an infiltrative nature to the myocardium. The exception is sarcoidosis, which, while uncommon, is occasionally encountered. It must, of course, be realized that within the three categories of cardiomyopathy, there can be some overlap.
The largest category of cardiomyopathies is the congestive or dilated cardiomyopathies. This condition is characterized by enlargement, sometimes massive, of the heart, with dilatation of all four chambers (Figure 3.4A). Probably the most common cause of dilated cardiomyopathy in America is chronic alcohol abuse. The myocardial damage in this case can be due to the direct toxic effect of the alcohol, the nutritional effects of chronic alcoholism, or the toxic effects of an additive to the alcohol (e.g., cobalt). Other causes of dilated cardiomyopathy are peripartum cardiomyopathy and chronic myocarditis. There is also an idiopathic form of dilated cardiomyopathy in which the cause is unknown.
Patients with peripartum cardiomyopathy present with heart failure during the last month of pregnancy or during the first 5 months postpartum.29 In approximately half the patients, the enlarged heart returns to normal within 6-12 months. Occasionally, sudden death occurs. There is some thought that this entity is a form of myocarditis secondary to an infectious, autoimmune or idiopathic process.
In dilated cardiomyopathy, the heart is markedly enlarged, with flabby myocardium and dilatation of all chambers. Mural thrombi are common. Microscopically, there is degeneration and/or hypertrophy of muscle fibers, focal or diffuse myocardial fibrosis, scattered mononuclear cell infiltrates, and, occasionally, fatty infiltrates.
Congestive cardiomyopathy has also been associated with certain toxic substances such as cobalt and adriamycin. The secondary cardiomyopathy due to toxic substances may be caused by the direct cardiac toxic action of the drug, an atypical reaction to it, or excessive doses of some of these substances, such as adriamycin. In all forms of congestive cardiomyopathy, sudden deaths occur and are recognized by both forensic pathologists and clinicians. Arrhythmias are, in fact, clinically associated with this condition.
The most interesting of the three cardiomyopathies is hypertrophic car-diomyopathy. It has also been known as idiopathic hypertrophic subaortic stenosis and hypertrophic obstructive cardiomyopathy. Hypertrophic cardiomyopathy is principally a familial cardiac disorder, with an autosomal dominant pattern of inheritance, said to be present in approximately 0.2% of the population.30 In this condition, there is massive myocardial hypertrophy without ventricular dilatation, in the absence of any cardiac or systemic disease that could produce these changes. The heart usually shows a disproportionate asymmetrical hypertrophy of the interventricular septum compared with the free wall of the left ventricle (Figure 3.4B). In some cases, however, the left ventricular hypertrophy is symmetrical, with thickening of both the septum and free wall. Ninety-five percent of the cases of hypertrophic cardiomyopathy show disarray in the ventricular myocardial fibers, with fibers running in all
directions in an apparent haphazard pattern and with the myocardial cells hypertrophied and bizarre. These bizarrely shaped and haphazardly arranged myocardial cells are typically seen in the septum. They are less common in the free wall. The haphazardly arranged bizarre cells are not specific for hypertrophic cardiomyopathy, but have been noted in a number of other conditions usually associated with left ventricular strain. The disarray, however, is not nearly so marked or extensive. Ventricular and supraventricular arrythmias are common in individuals with this condition.
Echocardiographic evidence of hypertrophic cardiomyopathy is usually present in one or more closely related family members. In adolescents and young adults, hypertrophic cardiomyopathy may be the most common cause of sudden cardiac death.
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