Catheter ablation of the atrioventricular junction with radiofrequency energy

Abstract

Catheter ablation of the atrioventricular junction using direct-current defibrillator discharges requires general anesthesia and may have serious side effects. Sixteen patients with drug-refractory supraventricular tachycardia underwent catheter ablation of the atrioventricular junction using radiofrequency energy. A standard 7F quadripolar electrode catheter was positioned to record the largest unipolar His potential (580 ± 640 μV) from the distal electrode. An electrocoagulator (Microvasive Bicap 4005) supplied continuous, unmodulated energy at 550 kHz. One to 14 applications of radiofrequency current were delivered between the distal electrode and a large-diameter chest wall electrode. Transient, mild chest discomfort was reported by seven of 16 patients. None had significant arrhythmmias or blood pressure changes during radiofrequency ablation. Complete atrioventricular block was produced in nine of 16 patients and high-grade second-degree atrioventricular block was produced in one patient with radiofrequency current. Attenuated His bundle electrograms could still be recorded in the remaining six patients, four of whom underwent successful atrioventricular junctional ablation using direct-current shock during the same session. Atrioventricular block persisted in all 10 patients successfully treated with radiofrequency ablation during a mean follow-up of 4.2 months. Compared with a group of historic control subjects treated with direct-current shock ablation, the 10 patients successfully treated with radiofrequency current had significantly less creatine kinase-MB isoenzyme release (5.7 ± 5.1 vs. 22 ± 13 IU, p = 0.006). A junctional escape rhythm was present in all patients after radiofrequency-induced atrioventricular block. In contrast, three of 10 control patients had an idioventricular escape after direct current shock ablation, and four patients had no escape rhythm at all. We conclude that 1) catheter ablation of the atrioventricular junction with radiofrequency current appears to be safe and successfully induced persistent atrioventricular block in 62% of patients; 2) radiofrequency ablation may result in more stable escape rhythms and less creatine kinase-MB isoenzymes release than direct-current shock ablation; and 3) a majority of patients with drug-refractory supraventricular tachycardia can be successfully treated with application of radiofrequency energy, whereas failure to achieve atrioventricular junctional ablation with this technique does not appear to mitigate against successful application of direct-current shock ablation.