Cardiac pathology in chronic myopathy, with particular reference to dystrophia myotonica.

Histological changes in the hearts of two patients with dystrophia myotonica and one patient with a familial scapulo-peroneal myopathy are described. The myocardium showed fibre hypertrophy, interstitial fibrosis, vacuolar degeneration of myocardial cells and focal groups of aberrantly orientated myofibres. The AV node in the case of scapulo-peroneal myopathy showed vacuolar fibre degeneration and fatty infiltration. The aberrantly orientated myofibres have not previously been described in this context, and their relationship to similar aberrant fibres in hypertrophic obstructive cardio-myopathy and the electrophysiological and clinical manifestations of cardiac involvement in myotonic dystrophy are discussed.