Overdrive Pacing from Downstream Sites on Multielectrode Catheters to Rapidly Detect Fusion and Diagnose Macroreentrant Atrial Arrhythmias
Background—Entrainment criteria for macroreentrant arrhythmias are based on detecting fusion between tachycardia and paced wavefronts, but this is often difficult for atrial tachycardias (AT) after ablation of atrial fibrillation.
Methods and Results—Using a multipolar catheter, pacing was performed from electrodes within the coronary sinus showing activation later than adjacent electrodes (downstream overdrive pacing (DOP) during 66 ATs in 62 patients: 20 cavotricuspid isthmus (CTI) dependent ATs, 20 perimitral ATs, 13 focal ATs with sequential coronary sinus (CS) activation, and 13 other macroreentrant left atrial ATs. The paced-CL (PCL) was 10-30 ms below the tachycardia cycle length (TCL) and activation at the neighboring upstream electrodes was assessed. DOP at 48 sites close to a macroreentrant circuit (PPI - TCL < 40 ms) produced constant fusion demonstrated by long stimulus to upstream atrial electrogram interval (S-Au) > 75% TCL and was consistent with orthodromic activation of the upstream site despite its close proximity to the pacing site. In contrast, DOP at 18 sites during focal AT or remote from the macroreentrant AT circuit (PPI -TCL > 40 ms) always demonstrated a comparatively short S-Au < 25% of TCL (12 ± 4% vs. 89 ± 4% of TCL, p < 0.001) consistent with direct activation.
Conclusions—Selection of a downstream activation site for overdrive pacing can facilitate rapid recognition of macroreentry and proximity to the reentry circuit using a single multielectrode catheter by recognizing a PPI - TCL < 40 ms and S-Au > 75% of TCL. Recognition of intracardiac constant fusion using this method is a novel criterion for transient entrainment.
- Received December 30, 2013.
- Revision received March 24, 2014.
- Accepted April 4, 2014.