Efficacy of permanent pacing in the management of high-risk patients with long QT syndrome

Background. From the international long QT syndrome (LQTS) study, 30 patients with corrected QT interval (QT_c) of more than 0.44 second^1/2 were identified who had permanent pacemakers implanted for management of recurrent syncope or aborted cardiac arrest. Methods and Results. Pacemakers were implanted on average 7 years after the onset of the first syncopal episode. Most of the patients were female (87%), the average age at implantation was 19±13 years, the mean QT_c was 0.55±0.08 second, and 57% were receiving antiadrenergic treatment for LQTS when the pacemaker was placed. Using birth as the time origin, the median cardiac event rate was significantly (p<0.001) reduced by pacing from 0.5 to 0 events per patient per year, with 21 patients experiencing no cardiac events during an average pacemaker follow-up of 49 months per patient. In 10 patients in whom the demand atrial pacing rate was faster than the intrinsic sinus rate, the average heart rate was increased 23 beats/min (from 58 to 81 beats/min) with pacing with reduction in the QT interval from 0.59 seconds to 0.46 seconds. Conclusions. The beneficial effects of pacing in high-risk LQTS patients probably relate to the prevention of bradycardia, pauses, and the shortening of long QT intervals - factors that are known to be arrhythmogenic in this syndrome. Permanent cardiac pacing reduces the rate of recurrent syncopal events in high-risk LQTS patients, but it does not provide complete protection.