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The cardiomyopathies are a relatively common group of serious diseases characterised by damage to the heart muscle. They form the most frequent indication for cardiac transplantation. There are three main types: hypertrophic (HCM), dilated (DCM) and restrictive cardiomyopathies. Duchenne and Becker muscular dystrophies often produce some very similar cardiac symptoms. A recent review (Towbin et al (1999) Nature Medicine 5(3) 266 - 267) suggests that contractile protein dysfunction predominantly gives rise to HCM, whereas defects in cytoskeletal proteins may produce DCM.
There is a first class American website on all types of cardiomyopathy maintained by the National Heart Lung and Blood Institute that is well worth visiting. It includes a useful glossary for beginners.
The post mortem specimen below illustrates some of the pathological changes seen in dilated cardiomyopathy. The left ventricle is grossly enlarged and the muscular walls are abnormally thin, in relation to the size of the ventricle. This is an image map, and the major features can be identified by pointing at them with the mouse.
These disorders may be due to alcohol toxicity, cobalt poisoning, Chagas disease or vitamin deficiency (e.g. vitamin B1 in Beri Beri). In some cases an autoimmune cause is suspected, as the onset of the disease is preceded by an episode of viral infection, and immunosuppressant drugs are occasionally found to be helpful. Badorff et al (1999) Nature Medicine 5(3) 320 - 326 have recently shown that enteroviral protease 2A from coxsackie virus cleaves dystrophin and suggest that this may be important in the pathogenesis of the disease. However, in the vast majority of cases, the underlying cause remains unknown.
Cardiac enlargement visible on chest X-rays creates a suspicion of dilated cardiomyopathy, but it is important to systematically eliminate all the other possible explanations for the patient's symptoms, and to treat any intercurrent diseases. Laboratory tests, even when these prove negative, can play a valuable role by excluding other possible pathologies, and thereby confirm that the preliminary diagnosis was in fact correct.
The following case is one of dilated cardiomyopathy. In common with many patients in clinical practice, the progress of the disease is complicated by a series of events which may appear at first sight to be unrelated to the cardiomyopathy. Closer investigation of the effects of cardiomyopathy on the functioning of other body systems will reveal, however, that many of the events in this case are linked to the original pathology.
You are provided with a complete day to day account of the progress of this patient, including tests requested by the consultants, the results of these tests, and decisions made concerning treatment. Short answer questions have been included in the case history, and in addition there are separate pages containing review questions on this exercise, a section on diagnostic tests and a complete list of drugs used to treat this patient, including their mechanisms and sites of action. You can find explanations for some of the technical terms and answers to many of the short answer questions by pointing at them with the mouse. Try first to tackle them unaided.
Try to interpret this information, and use the questions posed to:
Further reading: International Journal of Cardiology, Vol. 54, No. 2, May 1996. (This issue contains a series of articles on various aspects of cardiomyopathy. A copy is available in the counter collection at the Leeds Medical Library).