Adults with MMD1 and minor cardiac conduction defects benefit from invasive testing and possible pacemaker insertion
New evidence suggests that relatively aggressive management of seemingly minor cardiac conduction defects in adults with type 1 myotonic dystrophy (MMD1, or DM1) can prolong survival.
Slowing of signal conduction through the heart, a common effect of MMD1, was the subject of a recent study conducted in France. The investigators found that adults with minor electrical conduction system abnormalities detected on an electrocardiogram (EKG) benefited from invasive testing and selective placement of a pacemaker.
The study, published March 28, 2012, in the Journal of the American Medical Association, included 486 adults with MMD1 in whom a noninvasive, surface-electrode EKG revealed minor slowing of electrical signals through the heart's conduction system.
Of these 486 participants, 341 were assigned to an "invasive strategy" group, in which they received an invasive (inside the heart) electrophysiological study, with placement of a pacemaker if a measurement called the "HV interval" was greater than 70 milliseconds.
The other 145 participants were assigned to a "noninvasive strategy" group, in which they received regular surveillance but did not undergo either invasive testing or a pacing device unless their surface EKG showed a serious conduction defect.
The nine-year survival rate in the invasive strategy group was 76.7 percent. In the noninvasive strategy group, it was 69.2 percent.
The researchers suggest that the difference in survival rates was mostly attributable to a lower incidence of sudden death in the invasive strategy group. In the invasive group, the incidence of sudden death was 4.5 percent, while in the noninvasive group it was 18 percent.
They say that the lower incidence of sudden death in the invasive strategy group suggests that conduction-system disease is a major cause of sudden death in MMD1 that appears to be partially preventable by implementing an invasive management strategy.