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Idiopathic Cardiomegaly


Idiopathic cardiomegaly. Primary myocardial disease. Myocardosis. Idiopathic cardiac hypertrophy. Idiopathic cardiomyopathy. Cardiopathy. Nutritional heart disease. Cardiovascular collagenosis with parietal endocardial thrombosis. Dilated cardiomyopathy. Obscure cardiopathy, dilated ventricle type. Idiopathic hypertrophy of the heart in African children. Cryptogenic heart disease. Heart muscle disease. Congestive cardiomyopathy. Becker's disease (this synonym is still used, but Becker's disease or South African cardiomyopathy, is probably not a disease entity - WHO, 1989).


Idiopathic cardiomegaly has been defined as an acute, subacute or chronic disorder of heart muscle of unknown origin. Others have more simply called it "a large heavy heart for which there is no apparent cause." Inherent in the definition is exclusion of coronary atherosclerosis, Chagas' disease, AIDS, essential hypertension, and peripartum heart disease.

Geographic Distribution

Since idiopathic cardiomegaly is difficult to define precisely in either clinical or pathological terms the exact distribution is equally difficult to delineate: various forms of idiopathic cardiomegaly exist throughout the world. However, there is no doubt that this form of heart disease is more prevalent in much of the tropics than in colder climates and industrialized societies. If Chagas' disease, AIDS, peripartal anemia, thiamine deficiency, and ischemic or hypertensive heart disease are excluded, there is a residue of patients with large hearts without clearly defined cause. Cases are reported from West and South Africa, Brazil, the West Indies, India and elsewhere. The somewhat different peripartal or puerperal form is more universal, with published series from South, East and West Africa, Central and South America, Saudi Arabia, Korea, China, and the southern United States.


The cause is unknown: heart muscle disease may well be the end result of a variety of previous episodes of damage, although in a few patients a specific virus, chemical poison, parasite, or toxin can be implicated. Idiopathic cardiomegaly occurs at all ages, but is most common above over 30 years of age. There is no sex or racial predilection, but it may be more common in lower socioeconomic groups, possibly influenced by chronic malnutrition.


Macroscopically, there is nearly always a pericardial effusion, but it is seldom of clinical importance. The heart is dilated and hypertrophied and may weigh 800 g. Mural thrombi are common, particularly near the apex of the left ventricle. The cardiac valves and coronary arteries are normal (unless there is some coincidental disease). When the appropriate cardiac chamber enlarges sufficiently, there may be incompetence of either the mitral or tricuspid valve, or both.

Microscopically, there is hypertrophy of the myocardial fibers; this may be gross, with large bizarre nuclei. Cardiac connective tissue is increased, often with focal scarring. The endocardium is seldom thickened and the myocardium is soft, but there are small patches of fibrous tissue scattered throughout one or both ventricles. The papillary muscles are flattened. In almost all these hearts there are thrombi in the left ventricle and often in the right ventricle also; the thrombi are usually pale and firm but may be red and friable, which is probably a terminal finding. Thrombi are most common in the apices of the ventricles. Beneath a thrombus there is often granulation tissue containing chronic inflammatory cells; later this becomes a fibrous plaque.

The disease has been reported in an acute form, with large thrombi in the cardiac chambers, particularly the left ventricle, and associated thrombi in the pulmonary artery. In such patients the endocardium of the ventricles is swollen and thickened, with focal collections of inflammatory cells and hemorrhage.

The associated changes outside the heart are those of chronic venous congestion and multiple infarcts. Infarction is most common in the lungs, kidneys, spleen, and brain. Cirrhosis is not an associated finding in most parts of the world.

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Copyright: Palmer and Reeder