A novel method to define critical isthmus of left atrial tachycardia; late potential mapping during sinus rhythm

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. BACKGROUND: Atrial tachycardia (AT) is a commonly encountered rhythm disorder in patients with underlying atrial scar. The role of late potential (LP) based mapping in the detection of AT critical isthmus has yet to be systematically evaluated. PURPOSE: We aimed to investigate the relationship between the atrial LPs (ALP) localization in sinus rhythm and the critical isthmus of re-entrant ATs in patients with underlying atrial low-voltage areas. METHODS: Thirty-five symptomatic patients [mean age: 62 ±9, gender: 25 (71.4%) female] with left AT, who had undergone catheter ablation, were enrolled. Voltage and LP mapping were performed in sinus rhythm in both atriums. Low voltage areas and signals with continuous-fragmented morphology were tagged. Isochronal late activation mapping (ILAM) was also performed in all procedures. After induction of AT, activation mapping was performed during tachycardia in all patients to detect critical sites of the tachycardia. RESULTS: Activation mapping indicated single re-entry in 30 patients and ≥1 re-entry in 5 patients. Localized re-entry was observed in 20 (51.2%) patients, macro re-entry in 18 (46.1%), and biatrial re-entry in 1(2.5%). The mean fractionated electrogram duration in the AT termination site was calculated at 134.3±46.7 ms and the mean bipolar voltage at 0.17±0.12 mV. The ALPs were tagged in 25 (64.1%) patients on the anterior wall, 12 (34.3%) on the roof, 5 (12.8%) on the septal wall and 2 (5.7%) in the Bachmann’s Bundle region. All ALPs were in the latest activated zones of ILAM in patients with localized re-entry and predicted successful ablation sites to terminate the AT. Freedom from atrial tachyarrhythmias (ATAs) was 78.7% at six months during a mean follow-up duration of 338 ±226 days. CONCLUSION: Our findings demonstrated the utility of ALPs during sinus rhythm to predict the successful termination sites for left ATs. These areas displayed continuous-fragmented signal morphology during sinus/paced rhythm in correlation with the critical isthmus of AT detected during activation mapping. [Figure: see text] [Figure: see text]