Successful ablation of sinus node reentrant tachycardia using remote magnetic navigation system
Ablation of sinus node reentrant tachycardia (SNRT) may be difficult with risk of sinus node injury by using conventional catheters. We report successful ablation of SNRT by using remote magnetic navigation system (Stereotaxis). Case report A 50-year-old female was referred from another hospital for symptoms of paroxysmal palpitations. She was on beta-blocker for frequent palpitation. Holter monitoring revealed frequent paroxysmal episodes of narrow complex tachycardia at rates of 140-150 bpm.
... es of 140-150 bpm. Echocardiogram, thyroid function tests, and other routine lab parameters were normal. During electrophysiological evaluation, a narrow complex tachycardia (cycle length of 393 ms) was easily induced by programmed atrial stimulation. The surface electrocardiogram (ECG) P wave morphology during tachycardia was similar to sinus rhythm. The atrial activation sequence during tachycardia was earliest in the high right atrium followed by the His-atrial and coronary sinus atrial electrograms suggesting an origin in or around the region of the sinus node. Premature ventricular extrastimuli introduced during tachycardia when the His bundle was refractory did not advance the subsequent atrial cycle length or change the atrial activation sequence. An appropriately timed atrial premature extrastimulus delivered during tachycardia from a right atrial catheter reproducibly terminated tachycardia. Ventricular pacing was able to dissociate ventricular activity without affecting the atrial rate. These findings strongly suggested the diagnosis of sinus node reentrant tachycardia (SNRT). With remote magnetic navigation system (Stereotaxis, Inc, St Louis, MO, USA) and CARTO (Biosense Webster, Inc, Diamond Bar, CA, USA), mapping was performed during the tachycardia. The earliest atrial activation noted in the high lateral right atrium at the region of the sinus node. At this site, the atrial electrogram was 50 ms in duration and fragmented, initially negative in the unipolar tip electrogram, and 35 ms before onset of the surface ECG P wave. 1 At this site, ablation done with the irrigated tip catheter (Celsius RMT, Biosense Webster) using 30 W radio frequency (RF) energy and a maximum temperature of 458C. After initial acceleration, tachycardia terminated within 8.2 s. Radio frequency applications continue up to 60 s. After first RF application there was non-sustained SNRT induced using atrial-programmed stimulation. Further RF ablation was done at the region around the site of earliest activation to augment the ablation (Figure 1) . Subsequently, the tachycardia could not be re-initiated with atrial or ventricular pacing even with the presence of isoproterenol infusion. Total fluoroscopy time was 7.2 min. Follow-up 48 h telemetry monitoring revealed no recurrence of tachycardia. Sinus node reentrant tachycardia is an uncommon, but likely under diagnosed, form of supraventricular tachycardia, being easily confused with sinus tachycardia. Catheter ablation of SNRT is associated with risk of sinus node injury and thermal injury to the right phrenic nerve. Remote magnetic navigation provides enhanced catheter stability and substrate contact for the precise ablation. As per best of our knowledge we describe the first reported case of SNRT successfully ablated by using remote magnetic catheter navigation. Figure 1 Right atrium electro-anatomical map (right-lateral orientation). The dark red dots in high lateral right atrium indicate the successful ablation site of sinus node reentrant tachycardia. Published on behalf of the