Facioscapulohumeral muscular dystrophy: evidence for selective, genetic electrophysiologic cardiac involvement.

Facioscapulohumeral muscular dystrophy is an autosomal dominant disorder with an incidence of 3 to 10 cases per million. The only type of cardiac involvement ascribed to this neuromuscular disorder is a unique form of heart disease--permanent atrial paralysis. However, reported cases of facioscapulohumeral muscular dystrophy probably represented instead what is now recognized as phenotypically similar Emery-Dreifuss dystrophy. Cardiac involvement, therefore, has not been convincingly reported in facioscapulohumeral muscular dystrophy, but because of the clinical similarity of that disorder to Emery-Dreifuss dystrophy and its genetic variants, a prospective investigation of the electrophysiologic properties of the atria and atrioventricular (AV) node and infranodal conduction was undertaken in 30 rigorously documented cases of facioscapulohumeral muscular dystrophy. All patients had a 12 lead surface electrocardiogram (ECG), 22 had a 24 h ambulatory ECG, 15 patients had two-dimensional echocardiographic/Doppler studies and 10 patients underwent 12 intracardiac electrophysiologic investigations. Left atrial, right atrial or biatrial P wave abnormalities were present in 60% of the surface ECGs. Evidence of abnormal AV node or infranodal conduction was present on intracardiac electrophysiologic study or surface ECG in 27% of patients. Atrial flutter or fibrillation was induced by single atrial extra stimuli in 10 of the 12 intracardiac electrophysiologic studies. Sinus node function was abnormal in three patients. This investigation provides the first secure evidence of cardiac involvement in facioscapulohumeral muscular dystrophy. The involvement is represented by relatively high susceptibility to induced atrial flutter or fibrillation during electrophysiologic study, together with less frequent evidence of abnormal sinus node function and abnormal AV node or infranodal conduction.(ABSTRACT TRUNCATED AT 250 WORDS)