Pathohistological changes in endomyocardial biopsy specimens in patients with myotonic dystrophy

Endomyocardial biopsies in patients with myotonic dystrophy (MD) have, so far, shown changes such as myofibrillar degeneration, mitochondrial abnormalities, focal myocarditis, fibrosis and fatty infiltration of the myocardium and the conduction system.

This study presents the results of endomyocardial biopsy in 10 patients with MD. Endomyocardial biopsy was carried out using King's bioptome.

In two patients with servere MD biopsy specimens showed changes compatible with border line myocarditis. In five patients with moderate to severe forms of MD fibrosis and fatty infiltration of the myocardium were found in addition to degenerative changes and hypertrophy of muscle fibers. Three patients with mild MD had non-specific degenerative and hypertrophic myocardial changes. The histological changes described above were present in patients without cardiological symptoms and in those with normal ECG and echocardiographic findings. Only two of the 10 patients in whom endomyocardial biopsy was done complained of fatigue and occasional palpitations while the rest were asymptomatic. One patient with focal myocarditis had ECG signs of left bundle branch block and echocardiographic evidence of reduced left ventricular contractility. Five patients with signs of endomyocardial fibrosis only had an abnormal Q wave on ECG recordings. The remaining five patients with border line myocarditis i.e. with degenerative and hypertrophic myocardial changes had normal ECG and echocardiographic findings.

These results stress the significance of endomyocardial biopsy in detecting myocardial pathologic changes in patients with MD.