Endocardial unipolar voltage mapping of left atrial posterior wall after surgical epicardial radiofrequency ablation to accurately determine transmural scar
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Authors
Shigeta T.
Hussain S.
Honarbakhsh S.
Hunter R.
Providencia R.
Schilling R.
Ahsan,S.
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2025
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Conference Proceedings
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Introduction: The Convergent hybrid ablation procedure is often performed in patients with long standing atrial fibrillation. It consists of minimally invasive surgical epicardial ablation of the posterior wall, followed by endocardial catheter ablation. When an epicardial gap is suspected during linear ablation in the atrium, endocardial bipolar voltage mapping may have limitations in detecting the location of any gaps. A recent animal study reported that atrial unipolar voltage mapping might be useful to distinguish intramural-epicardial gap lesions from transmural scar lesions. We investigated unipolar voltage of the left atrial posterior wall following surgical epicardial ablation with the aim of identifying a voltage threshold which would confirm transmural scar Methods: Six patients undergoing the Convergent procedure were analyzed. The surgical epicardial ablation was performed homogenously at left atrial posterior wall, defined as the area enclosed by the pericardial reflection at left atrial roof, the line between the bottoms of inferior pulmonary veins, and the pulmonary vein ostiums. Endocardial catheter ablation was performed within 6 weeks-3 months after the surgical procedure. Before the endocardial ablation was performed, left atrial endocardial mapping was performed with a high-density mapping catheter on three-dimension mapping system during atrial pacing from the coronary sinus. After the procedure, offline analysis was performed to study unipolar voltage mapping of the left atrial posterior wall. Endocardial scar, was defined as bipolar voltage was set of less than 0.1 mV at first Then, additional analysis was performed with the threshold of less than 0.5 mV. When endocardial scar area was identified, it was regarded as a marker of transmurality from the previous surgical epidcardial ablation Results: Out of 1155 analyzed electrograms of left atrial posterior wall in 6 patients (age 63 60 - 74]), 696 were within the endocardial scar area namely the transmural scar area. When the threshold of bipolar voltage was set to 0.05 mV, 396 electrograms were within the transmural scar area. The mean unipolar voltage was significantly lower in the transmural scar area (0.41+/-0.32 mV for the transmural scar area vs. 1.08+/-0.98 mV for the gap area, p<0.01). This result was also confirmed when the threshold was set to 0.05 mV (0.33+/-0.29 mV for the transmural scar area vs. 0.86+/-0.83 mV for the gap area, p<0.01). The optimal endocardial unipolar voltage cutoff for the transmural scar was identified as 0.40 mV (AUC 0.81, sensitivity 60%, specificity 90%) and 0.33 mV (AUC 0.81, sensitivity 68%, specificity 86%) with the bipolar voltage threshold of 0.1 mV and 0.05 mV, respectively Conclusion(s): Unipolar voltage may be more accurate in identifying true transmural scar lesions after epicardial radiofrequency ablation of the left atrial posterior wall. This result may help in the detection of the conduction gap from linear ablation lesions.
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European Heart Journal