A strategy of implanting permanent cardiac pacing markedly improved survival for patients with myotonic dystrophy type 1 who presented with surface electrocardiogram manifestations of cardiac conduction abnormalities, compared with a noninvasive strategy of regular surveillance, according to a retrospective cohort study published March 28 in JAMA.
The likelihood of dying during a median 7.4 years of follow-up was nearly 40% lower among patients who underwent electrophysiological testing and, potentially, prophylactic pacing, than among those who did not undergo electrophysiological testing or pacing. The difference between the two groups was largely attributed to a decrease in sudden death in those who received a pacemaker or implantable cardioverter-defibrillator (ICD), said Dr. Karim Wahbi of the departments of cardiology and neurology at Cochin Hospital and the Myology Institute at Pitié-Salpêtrière Hospital, both in Paris, and his associates.
The study findings suggest that conduction system disease "is a major cause of sudden death that appears to be preventable" in this patient population, they noted.
Myotonic dystrophy type 1, also known as Steinert disease, is the most common inherited neuromuscular disease in adults and is characterized by muscle weakness, myotonia, multiple endocrine disorders, respiratory insufficiency, and cardiac abnormalities. As many as one-third of patients succumb to sudden death.
Both the American College of Cardiology and the American Heart Association recommend permanent pacing in patients with myotonic dystrophy type 1 when complete atrioventricular block or advanced high-degree atrioventricular block are detected, or prophylactically when first-degree atrioventricular or fascicular block are detected on ECG. However, whether this invasive approach actually prevents sudden death has never been assessed in a clinical study until now, Dr. Wahbi and his colleagues said.
Of 914 consecutive adults in the DM1 Heart Registry at the Myology Institute who were admitted during 2000-2009 for management of myotonic dystrophy type 1, 486 had ECGs showing minor conduction defects.
Of these subjects, 341 were managed invasively on the advice of their cardiologists. Electrophysiological testing in these patients found an HV interval greater than 70 ms in 164 patients and sustained ventricular tachyarrhythmias that were induced by programmed ventricular stimulation in 70 patients. The patients with an HV interval greater than 70 ms underwent placement of a pacemaker (150) or received an ICD (14). The remaining patients in the invasive-strategy group did not undergo a device implantation.
The remaining 145 subjects were managed noninvasively on the advice of their cardiologists. They had no electrophysiological study and no implantation of pacing devices, but were followed yearly by a neurologist and a cardiologist, both of whom specialized in muscular diseases.
Overall, 49 patients received antiarrhythmic drugs, including amiodarone and beta-blockers.
During a median follow-up of 7.4 years (range, 0-9.9 years), 80 patients died (50 in the invasive-strategy group and 30 in the noninvasive group), giving a 9-year overall survival of 74.4%. Survival at 9 years was 76.7% in the invasive strategy group and 69.2% in the noninvasive group.
After the data were adjusted to account for patient age, sex, history of supraventricular tachyarrhythmia, left ventricular ejection fraction, PR interval, QRS duration, and heart rate, the invasive strategy group had a hazard ratio of 0.61 for dying when compared with the noninvasive-strategy group (JAMA 2012;307:1292-301).
This difference was attributable mostly to the lower rate of sudden death in the invasive-strategy group (10 sudden deaths: 8 pacemaker recipients, 1 ICD recipient, and 1 patient without a pacing device), compared with those in the noninvasive strategy group (16 sudden deaths). "The 9-year cumulative incidence of sudden death was 4.5% in the invasive-strategy group and 18.0% in the noninvasive-strategy group," they added.
There were no significant differences between the two study groups in deaths due to respiratory failure or to other causes.
"While other studies are needed to confirm these findings, consideration of [the invasive] strategy may be prudent in this population, [who are] at higher than average risk for sudden death," Dr. Wahbi and his associates wrote.
This study was funded by the Association Française Contre les Myopathies. Dr. Wahbi reported no financial conflicts of interest, and two of his coauthors reported ties to Boston Scientific, Sorin Group France, Biotronik France, and Genzyme.