Entrainment to Distinguish Orthodromic Reciprocating Tachycardia from Atrioventricular Nodal Reentry Tachycardia in Children

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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. 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. 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. 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).