Standardized parallel pace-capture testing as a functional endpoint for lesion validation

Electrogram (EGM) metrics used to judge radiofrequency (RF) lesion quality are strongly influenced by catheter orientation and design. Whether pacing threshold can provide a robust functional marker of lesion integrity beyond EGM reduction remains uncertain.

This study aimed to determine how catheter-tissue angle and catheter type affect EGM voltage, peak frequency (PF), and pacing threshold in vivo.

12 swine underwent right atrial mapping. Using a contact force-sensing ablation catheter, EGMs and pacing thresholds were measured at nonablated sites (n = 83) and RF lesions (n = 75) with parallel (0°-20°) vs nonparallel contact (20°-90°). Separately, paired recordings at colocalized sites (n = 74 pairs) compared an HD Grid mapping catheter with the ablation catheter.

In nonablated myocardium, parallel contact increased unipolar and bipolar voltage and PF and lowered pacing threshold vs nonparallel contact (all P < .0001). Within lesions, voltage and PF were low and no longer angle dependent (P ≥ .53), whereas pacing threshold remained lower with parallel contact (median 2.2 vs 3.4 mA; P = .006), most prominently in insufficient lesions. At identical sites, HD Grid-derived omnipolar voltage and PF were higher than ablation catheter bipolar voltage and PF (both P < .0001).

Catheter orientation substantially alters EGM indices in nonablated myocardium. With RF lesions, standardized parallel pace-capture testing may provide functional information about residual excitability, whereas EGM cutoffs require catheter- and orientation-specific interpretation.