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Long-term follow-up of arrhythmias in patients with myotonic dystrophy treated by pacing

A multicenter diagnostic pacemaker study

Arnaud Lazarus, MD^*,*, Jean Varin, MD^*, Dominique Babuty, MD, Frédéric Anselme, MD, Joel Coste, MD^* and Denis Duboc, MD^*

^* Service de Cardiologie et de Biostatistique, Hôpital Cochin, Paris France
InParys, Saint Cloud, France
Service de Cardiologie, Hôpital Trousseau, Tours, France
Service de Cardiologie, Hôpital Charles Nicolle, Rouen, France

View larger version (18K): [in a new window]   Figure 1 Diagnostic algorithm for bradycardic events. In addition to a backup rate (basic), a watch rate (50 beats/min) and a pause rate (30 beats/min) are defined. The spontaneous ventricular rate (Vs) may fall below the backup rate to the pause rate, at which point ventricular pacing (Vp) is initiated. (A) A "pause" is confirmed after two consecutive ventricular cycles paced at the pause rate of 30 beats/min, triggering the memorization of a marker chain. (B) A marker chain of "bradycardia" is stored after 100 consecutive ventricular cycles between the watch and pause rates. Thereafter, rescue ventricular pacing begins, gradually rising to the backup rate. Open circle = Vs; Closed circle = Vp. Vs = ventricular sensed event; Vp = ventricular paced event.

View larger version (25K): [in a new window]   Figure 2 Marker chain of paroxysmal complete atrioventricular block. The intervals displayed correspond to RRs or PPs intervals. P = spontaneous P-wave; R = spontaneous R-wave; V = paced ventricle.

View larger version (11K): [in a new window]   Figure 3 Kaplan-Meier analysis of the incidence of bradyarrhythmias observed during follow-up, diagnosed as "pauses" by the pacemaker algorithm, and corresponding to either complete sino-atrial block (SAB) or high-degree atrioventricular block (AVB).

View larger version (13K): [in a new window]   Figure 4 Kaplan-Meier analysis of the incidence of atrial and ventricular tachyarrhythmias observed during the follow-up period.

View larger version (90K): [in a new window]   Figure 5 In March 1994, the presence of asymptomatic conduction disturbances on the surface electrocardiogram (ECG) prompted electrophysiologic testing in this 51-year-old woman with myotonic dystrophy. After the finding of a prolonged HV interval (70 ms), a pacemaker was implanted. During the first month after implantation, marker chains of paroxysmal high-degree atrioventricular (AV) block were recorded. In September 2000, 2:1 AV block was observed on the surface ECG. In March 2002, pacemaker dependency was demonstrated during temporary pacemaker inhibition, with underlying complete AV block, as shown on this ECG tracing (paper speed 25 mm/s).