Significance of late ventricular potentials in myotonic dystrophy.

In 39 patients with myotonic dystrophy, we found a high percentage of infrahissian cardiac conduction abnormalities (51%) and late potentials (46%), whereas spontaneous and inducible ventricular arrhythmias were rare. These results suggest that the prolongation of QRSD and the duration of the low-amplitude signal on the signal-averaged electrocardiogram were related to delayed activation of the His and Purkinje tissue rather than true late potentials.