Persistence of single echo beat inducibility after selective ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia: relationship to the functional properties of the atrioventricular node and clinical implications.

INTRODUCTION

Residual slow pathway conduction with or without reentrant echo beats has been reported in 25% to 30% of patients undergoing ablation for AV nodal reentrant tachycardia (AVNRT).

METHODS AND RESULTS

Fifty-eight consecutive patients (aged 45 +/- 12 years) with slow-fast AVNRT underwent radiofrequency catheter ablation of the slow AV nodal pathway (SP). Residual slow-fast echo beat was documented in 21 (36%) of 58 patients (group A). The pre- and postablation AH intervals triggering the echo beats were similar (346 +/- 8 msec vs 352 +/- 6 msec, P = NS), as were the pre- and postablation echo zones (55 +/- 6 msec vs 52 +/- 5 msec, P = NS) and functional refractory period of the SP. A consistent prolongation of the AV nodal effective refractory period (AVN-ERP; from 265 +/- 28 msec to 340 +/- 50 msec, P < 0.001) and the Wenckebach cycle length (WBCL; from 298 +/- 41 msec to 438 +/- 43 msec, P < 0.001) was observed in all patients with abolition of SP conduction (group B). In group A patients, the prolongation of WBCL was less (285 +/- 33 msec preablation, and 334 +/- 41 msec postablation, P < 0.001). Additional pulses abolished the residual echo in 16 of 21 patients, and further prolongation of the AVN-ERP and WBCL comparable to those found in patients without a residual echo beat was observed. During 19 +/- 8 months follow-up, no patient had clinical recurrence of AVNRT.

CONCLUSION

Residual single echo beat after SP ablation for AVNRT reflects the persistence of some portion of the SP with unchanged functional conduction properties whose prognostic significance is uncertain. A consistent increase of WBCL can be a reliable marker of complete abolition of slow pathway conduction and termination of AVNRT.