Low clinical recurrence and procedure benefits following treatment of common atrial flutter by electrogram-guided hot spot focal cryoablation

Background: The study sought to evaluate whether electrogram-aided identification of hot spot targets produces additional clinical and/or procedure benefits when using a non-traditional focal cryo ablation method to treat common atrial flutter. Methods: A preliminary study identified a specific electrogram criterion (e.g., a stimulus to onset of electrogram time of 74 [± 5] ms) that produced successful cryo testing plus subsequent cryoablation with demonstrable bi-directional isthmus block created at intervention site. In the present study, 26 consecutive patients with symptomatic common atrial flutter were ablated with a 9FR 8 mm tip cryo catheter using electrogram-aided identification of hot spot targets with a stimulus to onset of electrogram time of ≥70 ms. Outcomes measured were bi-directional isthmus block at intervention, symptom and conduction recurrence at 3 month follow-up, symptom recurrence at 6 month follow-up, and procedure characteristics. Results: Acute success rate at intervention was 100%. The percentage of patients with symptom recurrence by 3 month follow-up was 4.5% and no additional patients had arrhythmia symptoms documented by 12 month follow-up. Repeat electrophysiological study (EPS) at 3 month follow-up identified 44% of patients with conduction recurrence. The mean ± SD number of cryo tests and ablations were 11 ± 9 and 2 ± 1, respectively. Procedure, fluoroscopy and cryoapplication times were 77 ± 29 min, 11 ± 7 min, and 28 ± 11 min, respectively. Conclusions: A high acute success rate, plus low long-term clinical recurrence rate and procedure benefits may be achieved with electrogram-aided identification of hot spots for focal cryo ablation treatment of common atrial flutter using a 9FR 8 mm tip cryo catheter. The population of patients who were asymptomatic and had demonstrated conduction recurrence on repeat EPS at 3 month follow-up require close scrutiny over the long-term to ascertain whether they eventually experience arrhythmic symptoms. However, should these patients remain symptom-free over the long-term it would suggest that the entire isthmus may not be needed to support symptomatic common atrial flutter.