[Function of the heart conduction system in patients with progressive muscular dystrophy]

Intracardiac electrophysiologic studies were carried out in 9 patients with progressive muscular dystrophy. Diagnostic stimulation of the heart demonstrated no sinus mode dysfunction. The intra-atrial conduction time increased to 72 +/- 7.1 ms (p less than 0.05), and the interatrial conduction time, to 97 +/- 12.5 ms (p greater than 0.05) in response to shortened testing stimulus delay in 3 patients. All 9 patients showed great variation in the duration of effective refractory atrial and atrioventricular periods (97.0 +/- 12.5 ms). The H-V interval increased from 43.9 +/- 4.3 to 73.9 +/- 7.6 ms (p less than 0.01) in response to shortened delay in 7 of 9 patients. Atrial pre-excitation resulted in a block of the right and left limbs of the His bundle in 5 of 7 patients. Third-degree atrioventricular block was recorded by continuous ECG monitoring in 7 patient. It is suggested that an apparent or latent intraventricular conductivity disorder may be present in most cases of progressive muscular dystrophy.