Why the study?
Mitral isthmus gap conduction is common despite ethanol infusion into the vein of Marshall and endocardial ablation, prompting investigation of distal coronary sinus electrogram characteristics to guide gap identification.
Does distal coronary sinus electrogram analysis during left atrial appendage pacing improve the identification of gap conduction and achievement of mitral isthmus block in patients undergoing EI-VOM and endocardial ablation?
Does distal coronary sinus electrogram analysis during left atrial appendage pacing improve the identification of gap conduction and achievement of mitral isthmus block in patients undergoing EI-VOM and endocardial ablation?
Analyzing distal coronary sinus electrograms during left atrial appendage pacing effectively identifies epicardial versus endocardial gap conduction, facilitating high rates of mitral isthmus block.
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Distal CS electrogram guidance may facilitate mitral isthmus block; this Level 3 finding leaves open whether it improves outcomes versus standard techniques.
Background Mitral isthmus (MI) gap conduction is common despite ethanol infusion into the vein of Marshall (EI-VOM) and endocardial ablation of the MI. This study aimed to investigate the characteristics of electrograms of the distal coronary sinus (CSd) to guide the identification of the gap location in the MI. Methods A total of 187 patients who underwent EI-VOM and MI ablation were included in the study. After routine completion of EI-VOM and endocardial MI ablation, the characteristics of the electrogram in the CSd during left atrial appendage (LAA) pacing were analyzed in unblocked MI conduction. Results Among the 187 patients, 43.3% (81/187) had unblocked MI following EI-VOM and linear lesion creation in the endocardium. In patients with unblocked MI, 84.0% (68/81) showed double potential in the CSd during LAA pacing, among whom 80.9% (55/68) presented with an earlier high-frequency near-field potential (NFP) followed by a low-frequency far-field potential (FFP), suggesting an epicardial gap, whereas 19.1% (13/68) presented with FFP followed by NFP, suggesting an endocardial gap. In patients with single-potential in CSd (16.0%, n = 13), simple activation mapping of the endocardium and CSd revealed the gap location. Intra-CS ablation was necessary in 77.8% (63/81) of the patients, with a mean of 1.3 ± 1.7 sites and 1.1 ± 0.4 min for ablation. Eventually, 95.7 % (179/187) of the patients achieved MI blockage. These findings were confirmed in an external validation cohort, which demonstrated the effectiveness and efficiency of CSd potential-guided gap identification. Conclusion The characteristics of the electrograms in the CSd could aid in the prompt identification of the gap(s) location of the MI in patients with unblocked MI conduction. CLINICAL PERSPECTIVE What is Known: Bidirectional mitral isthmus conduction block is challenging despite EI-VOM and endocardial ablation. What the Study Adds: The characteristics of the electrogram at the CSd during left atrial appendage pacing could facilitate prompt identification of gap conduction in mitral isthmus mediated by the epicardium or endocardium. ver 2/3 of patients had an epicardial gap conduction that warranted intra-CS ablation. blockage rate is achievable using the CSd electrogram guided gap identification approach, with efficiency and effectiveness.
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Li et al. (2024) studied this question.
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