Key result
Myotonic muscular dystrophy is linked to progressive HV prolongation in ~78% of patients over time.
Why the study?
The progression of conduction system disease in myotonic muscular dystrophy and its electrophysiologic predictors were not well characterized.
Cohort (n=9)
Serial electrophysiologic studies fail to predict the progression of conduction disease in myotonic muscular dystrophy, suggesting testing should be reserved for symptomatic patients.
HV progression common without predictors in myotonic dystrophy; hypothesis-generating for serial monitoring before practice change.
To evaluate the progression of conduction system disease in myotonic muscular dystrophy, nine patients underwent serial electrophysiologic studies at a mean of 35 months apart. At the initial study, seven patients had first-degree atrioventricular block and three of these seven had disease in the His-Purkinje system (HV greater than 55 msec). At the second study, seven patients had prolonged HV intervals, and during the almost 3-year period, HV intervals increased by at least 5 msec in all seven patients. No electrophysiologic or electrocardiographic measures could be found that correlated with progression of conduction disease in these patients. Because of the failure of electrophysiologic measures to predict progression of conduction disease in these patients, electrophysiologic studies are recommended only for symptomatic patients. If significant disease is found in either impulse formation or conduction, permanent pacemaker therapy is warranted.
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Prystowsky et al. (1979) conducted a cohort in Myotonic muscular dystrophy (n=9). Natural disease progression was evaluated on Progression of conduction system disease (HV interval prolongation). Over a mean of 35 months, HV intervals increased by at least 5 msec in 7 of 9 patients with myotonic muscular dystrophy, with no baseline measures predicting this progression.