Radiofrequency Catheter Modification of the Sinus Node for “Inappropriate” Sinus Tachycardia
Authors: Lee Randall J. , Kalman Jonathan M. , Fitzpatrick Adam P. , Epstein Laurence M. , Fisher Westby G. , Olgin Jeffrey E. , Lesh Michael D. , Scheinman Melvin M. 
Published: June 2012

Background
Radiofrequency catheter ablation is the treatment of choice for patients with paroxysmal supraventricular tachycardias refractory to medical therapy. However, in symptomatic patients with inappropriate sinus tachycardia resistant to drug therapy, catheter ablation of the His’ bundle with permanent pacemaker insertion is currently applied. We evaluated the safety and efficacy of radiofrequency modification of the sinus node as alternative therapy for patients with inappropriate sinus tachycardia.

Methods and Results
Sixteen patients with disabling episodes of inappropriate sinus tachycardia refractory to drug therapy (4.2±0.3 drug trials) underwent either total sinus node ablation or sinus node modification. The region of the sinus node was identified as the region of earliest atrial activation in sinus rhythm during electrophysiological study. This region was further defined by use of intracardiac echocardiography (ICE) in 9 patients, in whom it was found that an ablation catheter could be guided reliably and maintained on the crista terminalis. Radiofrequency energy was delivered during tachycardia between either a standard 4-mm or custom 10-mm thermistor-imbedded catheter tip and a skin patch. Total sinus node ablation was performed successfully in all 4 patients in whom it was attempted and was characterized by a junctional escape rhythm. Sinus node modification was successfully achieved in all 12 patients in whom it was attempted and was characterized by a 25% reduction in the sinus heart rate. For the group as a whole, exercise stress testing after ablation revealed a gradual chronotropic response, with a significant reduction in maximal heart rate (132.8±6.5 versus 179.5±3.6 beats per minute [bpm];
P
<.001) without evidence of an exaggerated heart rate response to a light workload (103.0±4.1 versus 139.5±3.5 bpm;
P
<.001). Twenty-four-hour ambulatory ECG monitoring revealed a significant decrease in maximal heart rate and mean heart rate after ablation (167.2±2.6 versus 96.7±5.0 bpm,
P
<.001, and 125.6±5.0 versus 54.1±5.3 bpm,
P
<.001, respectively). There was a significant decrease in the number of applications of radiofrequency energy required in patients undergoing modification of the sinus node when guided by ICE compared with fluoroscopy alone (3.6±0.8 versus 10.4±2.1;
P
<.01) as well as a decrease in fluoroscopy time (33.0±9.5 versus 58.5±8.4 minutes). After a mean follow-up period of 20.5±0.3 months, there were no recurrences of inappropriate sinus tachycardia in patients who underwent a total sinus node ablation. However, 2 patients who had a total sinus node ablation subsequently required permanent pacing because of symptomatic pauses, and 1 patient developed an ectopic atrial tachycardia. After a mean follow-up of 7.1±1.7 months, there were two recurrences of inappropriate sinus tachycardia in patients who underwent sinus node modification. However, no significant bradycardia or pauses were observed. Complications encountered during the study included 1 patient who developed transient right diaphragmatic paralysis and another patient who developed transient superior vena cava syndrome.

Conclusions
Sinus node modification is feasible in humans and should be considered as an alternative to complete atrioventricular junctional ablation for patients with disabling inappropriate sinus tachycardia refractory to medical management. Sinus node modification may be aided by ICE.