Entrainment to distinguish orthodromic reciprocating tachycardia from atrioventricular nodal reentry tachycardia in children.

Background: Studies in adults suggest that after entrainment from the right ventricle, a post-pacing interval (PPI) minus tachycardia cycle length (TCL), when corrected for atrioventricular node delay (cPPI-TCL), is useful to distinguish atrioventricular nodal reentry tachycardia (AVNRT) from orthodromic reciprocating tachycardia (ORT), but this has not been evaluated in children.

Methods: In 100 children undergoing catheter ablation, entrainment of ORT or AVNRT was performed from the right ventricular apex. The atrial-His (AH) interval was measured on the return cycle (post-AH) and during tachycardia just prior to pacing (pre-AH). The cPPI-TCL was calculated as (PPI-TCL) - (post-AH - pre-AH). In the first 50 children, the best cutoff was identified and then validated in the next 50 children.

Results: In the first 50 children, cPPI-TCL was longer in AVNRT compared with ORT (122 +/- 19 ms vs 63 +/- 23 ms, P < 0.001). Furthermore, cPPI-TCL exceeded 95 ms in all AVNRT patients, but was less than < 95 ms in 28 of 29 ORT patients. In the next 50 children, a cPPI-TCL < 95 ms was 100% specific for ORT; a cPPI-TCL > 95 ms was 95% specific for AVNRT. There was even greater separation of cPPI-TCL values comparing AVNRT with ORT utilizing a septal accessory pathway.

Conclusions: The cPPI-TCL is a useful technique to distinguish AVNRT from ORT in children. Our data suggest that in children a cPPI-TCL < 95 ms excludes AVNRT, while a value > 95 ms is rarely observed in ORT. This technique is particularly useful to distinguish AVNRT from ORT utilizing a septal accessory pathway. (PACE 2010; 469-474).