The purpose of this study was to assess the clinical efficacy of radiofrequency ablation
of the slow pathway in patients with documented but noninducible paroxysmal supraventricular
tachycardia (PSVT) who have evidence of dual atrioventricular (AV) node pathways.
Patients with a documented history of PSVT at times do not have inducible PSVT in
the electrophysiology laboratory. Because dual AV node pathways serve as the substrate
for AV node reentrant tachycardia (AVNRT), ablation of the slow pathway potentially
may be useful in these patients.
The subjects in this prospective study were seven consecutive patients who underwent
an electrophysiologic procedure because of documented PSVT and were found to have
dual AV node physiology or inducible single AV node echo beats, but no inducible PSVT
despite the administration of isoproterenol and atropine. Their mean (+/- SD) age
was 33 +/- 13 years, and they had been symptomatic for 12 +/- 12 years. The frequency
of the episodes of PSVT ranged from > or = 1/day to 1/month. The rate of the documented
episodes ranged from 170 to 260 beats/min, and discrete P waves were not apparent.
Slow pathway ablation was performed with 9 +/- 4 applications of radiofrequency energy
using a combined anatomic and electrogram mapping approach.
All evidence of dual AV node pathways was eliminated in six patients, and dual AV
node physiology remained present in one patient. During a mean follow-up period of
15 +/- 10 months (range 8 to 27), no patient had a recurrence of symptomatic tachycardia
(success rate 95% confidence interval 65% to 100%).
Slow pathway ablation may be clinically useful in patients with documented but noinducible
PSVT who have evidence of dual AV node pathways.