Electrogram Characteristics of Ablated and Non-Ablated Myocardium in Humans: A Comparison of Miniaturized Embedded Electrodes and Conventional Ablation Electrodes.

INTRODUCTION: Intracardiac electrogram voltage remains an important metric for radiofrequency lesion application. Embedded micro-electrodes within ablation catheters are now approved for use in humans. OBJECTIVE: This study examined electrogram characteristics of miniaturized electrode bipoles (iEGMmini ) compared to distal ablation tip bipoles (iEGMstandard ) in the setting of typical atrial flutter in humans. METHODS: This was a single-center prospective trial involving 21 patients. A total of 54 non-ablated and 56 ablated sites were analyzed offline by separate blinded observers for iEGM voltage after a clinically successful radiofrequency (RF) ablation for typical atrial flutter. Ablation sites were defined as sites that were localized anatomically within the RF lesion set and did not have atrial capture at 10 mA and 2 milliseconds. Non-ablated sites were defined as sites adjacent to or remote from the ablation lesion set with capture at 10 mA and 2 milliseconds. RESULTS: iEGMmini had greater voltages at non-ablated sites and lower voltages at ablated sites than iEGMstandard (non-ablated sites iEGMstandard 0.64 mV vs. iEGMmini 1.0 mV; ablated sites iEGMstandard 0.15 mV, iEGMmini 0.08 mV, P < 0.001). The difference for each patient between ablated and non-ablated sites was greater for iEGMmini compared to iEGMstandard (0.94 mV ± 0.57 iEGMmini vs. 0.52 mV ± 0.35 iEGMstandard , P < 0.001). Inter-observer agreement was good among all non-ablated sites and iEGMmini ablated sites, but was less robust for ablated sites using iEGMstandard . CONCLUSIONS: Imbedded mini-electrode iEGM bipoles had higher voltages in non-ablated tissue, lower voltages in ablated tissue, and significantly greater intra-patient differences between ablated and non-ablated sites. These data suggest a potential role for miniaturized electrode bipole use in RF lesion monitoring.