A 24 year old man collapsed, clutching his chest, while pushing a motor car. Resuscitation attempts were unsuccessful. He had previously lost consciousness while weightlifting. There was no history of drug abuse.

At postmortem examination the heart weighed 430 g, normal for an 83 kg man. Cut section of the myocardium showed a 4 cm area of fibrosis in the lateral free wall of the left ventricle (fig 1). The epicardial coronary arteries had normal origin and no stenoses. The cardiac valves were normal. There was severe pulmonary oedema (right lung 800 g, left lung 550 g).

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Figure 1

Cross section of both ventricles showing fibrosis in the lateral free wall of the left ventricle.

Histology showed that the area of fibrosis was associated with many abnormal small intramural arteries with thickening of the media, intima, or both (fig 2). Extensive sampling (more than 20 sections) of the ventricles and atria showed the myocardium and small coronary vessels elsewhere were normal. No myocardial disarray was seen. The epicardial coronary arteries showed minimal intimal thickening. Vessels in the lung, kidney, spleen, and aorta were all normal.

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Figure 2

Section from the area of fibrosis showing vessel with notable intimal thickening (elastic van Gieson stain).

Fibromuscular dysplasia is best recognised in the renal arteries and can affect the epicardial coronary arteries. Fibromuscular dysplasia of small coronary arteries has been described in several conditions: hypertrophic cardiomyopathy, Friedreich's ataxia, scleroderma, prolonged QT interval, Marfan's syndrome, progressive muscular dystrophy, tunnel aortic stenosis, mitral valve prolapse, and in the sinus node artery in sudden death.1-4 Many of these studies are based on small numbers and some have no control group. The best documented is hypertrophic cardiomyopathy in which such abnormal vessels are not only frequently seen (83% of hearts compared with 9% of controls) but also present in large numbers.3 The abnormal vessels are often seen in areas of fibrosis and have been identified in infants. It is likely that the fibrosis is secondary to (rather than a cause of) the abnormal vessels.

The striking feature of our case is the regional nature of the abnormality. Recently hamartoma of mature cardiac myocytes was described5 in which discrete areas of hypertrophied disorganised myocytes were associated with thickened intramural vessels. The absence of myocardial disarray in our case is contrary to the diagnosis of hypertrophic cardiomyopathy. This pattern of regional fibrosis associated with fibromuscular dysplasia of intramyocardial arteries does not appear to have been described before. It seems likely that the fibrosis was secondary to the vascular abnormality; and the likely mechanism of sudden death was an arrhythmia. The regional nature of the abnormality raises the possibility of a congenital disorder, but there was no family history of heart disease, and investigation of several family members was negative. This case emphasises the importance of histology in myocardial fibrosis in the presence of normal epicardial coronary arteries.