An optimal output and electrode configuration for evaluating tissue transmurality - a preclinical study

Achieving transmural lesions is critical for durable outcomes in catheter ablation. While electrogram amplitude reduction and pacing threshold changes have been reported as useful parameters, the optimal electrode configuration and cutoff values remain unclear. This preclinical study evaluated the efficacy of conventional and microelectrode configurations in predicting transmurality using the QDOT MICRO catheter. Radiofrequency ablation was performed in 14 swine, creating 131 atrial lesions. Pacing thresholds and electrogram amplitudes were measured before and after ablation using three configurations: conventional bipolar, microelectrode bipolar, and unipolar. Lesion transmurality was determined histologically. Receiver operating characteristic analyses were conducted to assess predictive accuracy. Among all configurations, the conventional bipolar (A1–A2) showed the highest predictive value. Post-ablation bipolar amplitudes were lower in transmural lesions (AUC 0.777, 0.86mV), with greater amplitude reduction (64.4% vs. 40.5%, AUC 0.682). Pacing thresholds increased significantly after ablation and were higher in transmural lesions; the A1–A2 configuration had the highest accuracy in predicting transmurality (AUC 0.880, cutoff 3.4 V). Microelectrodes demonstrated inconsistent patterns, and even when the best configurations were selected, they remained less accurate than conventional bipolar measurements. Furthermore, morphological changes, including disappearance of R-waves (bipolar) and S-waves (unipolar), showed limited predictive value (AUCs ≤ 0.77 and ≤ 0.56, respectively). Conventional bipolar electrodes outperformed microelectrode configurations in assessing transmurality via electrogram amplitude and pacing threshold. Tip-to-ring bipolar pacing with the QDOT-MICRO catheter most effectively assesses atrial lesion transmurality, with 3.4 V as the optimal threshold.