RADIOFREQUENCY CATHETER MODIFICATION OF THE SINUS NODE FOR INAPPROPRIATE SINUS TACHYCARDIA

Background Radiofrequency catheter ablation is the treatment of choice for patients with paroxysmal supraventricular tachycardias refractory to medical therapy. However, in symptomatic patients with inappropria te sinus tachycardia resistant to drug therapy, catheter ablation of t he 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 inappropria te sinus tachycardia. Methods and Results Sixteen patients with disabl ing episodes of inappropriate sinus tachycardia refractory to drug the rapy (4.2+/-0.3 drug trials) underwent either total sinus node ablatio n or sinus node modification. The region of the sinus node was identif ied 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 fou nd that an ablation catheter could be guided reliably and maintained o n the crista terminalis. Radiofrequency energy was delivered during ta chycardia between either a standard 4-mm or custom 10-mm thermistor-im bedded catheter tip and a skin patch. Total sinus node ablation was pe rformed successfully in all 4 patients in whom it was attempted and wa s 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 maxi mal 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 l ight workload (103.0+/-4.1 versus 139.5+/-3.5 bpm; P<.001). Twenty-fou r-hour ambulatory ECG monitoring revealed a significant decrease in ma ximal heart rate and mean heart rate after ablation (167.2+/-2.6 versu s 96.7+/-5.0 bpm, P<.001, and 125.6+/-5.0 versus 54.1+/-5.3 bpm, P<.00 1, respectively). There was a significant decrease in the number of ap plications of radiofrequency energy required in patients undergoing mo dification of the sinus node when guided by ICE compared with fluorosc opy alone (3.6+/-0.8 versus 10.4+/-2.1; P<.01) as well as a decrease i n fluoroscopy time (33.0+/-9.5 versus 58.5+/-8.4 minutes). After a mea n follow-up period of 20.5+/-0.3 months, there were no recurrences of inappropriate sinus tachycardia in patients who underwent a total sinu s node ablation. However, 2 patients who had a total sinus node ablati on subsequently required permanent pacing because of symptomatic pause s, and 1 patient developed an ectopic atrial tachycardia. After a mean follow-up of 7.1+/-1.7 months, there were two recurrences of inapprop riate sinus tachycardia in patients who underwent sinus node modificat ion. However, no significant bradycardia or pauses were observed. Comp lications encountered during the study included 1 patient who develope d transient right diaphragmatic paralysis and another patient who deve loped transient superior vena cava syndrome. Conclusions Sinus node mo dification is feasible in humans and should be considered as an altern ative to complete atrio-ventricular junctional ablation for patients w ith disabling inappropriate sinus tachycardia refractory to medical ma nagement. Sinus node modification may be aided by ICE.