Introduction: Myotonic dystrophy (DM) is an inherited multisystem disorder associated with myotonia, progressive skeletal muscle weakness and atrophy, involvement of peripheral and central nervous system and sudden death likely due to atrioventricular block and/or ventricular arrhythmia.
Aim of the study: to assess the type and degree of cardiac and neurological involvement in patients (pts) with DM.
Materials and methods: 10 pts (6 male), in mean age of 35 +/- 13 years, treated for DM type I (DM1)--7 pts and type II (DM2)--3 pts. All pts underwent a neurological examination including muscle strength assessment as well as cardiac diagnostics including: standard and 48-hour ambulatory electrocardiogram, echocardiographic examination, magnetic resonance imaging (MRI) of the heart and late potentials assessment.
Results: Muscle strength was moderately diminished (46-48 points in MRC sub score) in 3 pts with DM1 and mildly diminished (56-58 points in MRC sub score) in 2 pts with DM2. These patients showed clinical symptoms of myopathy. Cardiovascular examinations revealed: QRS duration above 110 ms in 5 pts, clinically significant supraventricular arrhythmia or atrioventricular block in 3 pts, focal myocardial fibrosis in 3 pts, asymmetric hypertrophy of inter-ventricular septum in 1 patient, presence of late potentials in 5 pts. We have not observed correlation between impaired muscle strength and cardiac abnormalities. However, most pronounced cardiac abnormalities were observed in 2 male DM1 patients with clinical symptoms of myopathy and lowest MRC score. At a mean follow up of 3.2 +/- 1.4 years none of the pts died.
Conclusions: Cardiac involvement in pts with myotonic dystrophy is frequent and is characterized by phenotypic heterogeneity. Detection of cardiac abnormalities may require extensive diagnostics. The most important is the assessment of ECG. Cardiac and neurological abnormalities vary in intensity between patients without close relationship to each other.