From anatomy to ablation: intracardiac echocardiography-guided cavotricuspid isthmus morphology and procedural outcomes in typical atrial flutter

Background Cavotricuspid isthmus (CTI) ablation is the standard treatment for typical atrial flutter (AFL), yet marked anatomical variability can influence procedural workload and outcomes. Intracardiac echocardiography (ICE) allows direct visualisation of isthmus morphology and may guide ablation strategy. Purpose To assess whether an ICE-derived CTI morphology score predicts ablation workload and clinical outcomes during fluoroless CTI ablation for typical AFL. Methods In a retrospective cohort of 200 consecutive patients undergoing CTI ablation guided by three-dimensional electroanatomical mapping and ICE, CTI anatomy was graded with a 0–6 morphology score combining five features: CTI length > 35 mm (1), pouch (1), ridge (1), thick or prominent Eustachian valve (2), and concave shape (1). Primary endpoints were radiofrequency (RF) ablation time and number of applications. Secondary endpoints were acute bidirectional CTI block and late AFL recurrence (> 3 months). Results Grades were mild 0–1 (58.5%), moderate 2–3 (35.5%), and severe 4–6 (6.0%). Acute block was achieved in 99.5%. Each 1-point higher CTI score predicted greater workload: approximately +50 s RF time and +4 additional applications per point (both p < 0.001). The score was not associated with acute success but showed a trend toward higher late AFL recurrence (7.0% overall). Complications were rare (1% groin haematoma). Conclusion(s) An ICE-derived CTI morphology score provides a reproducible intra-procedural measure of anatomical complexity, predicting ablation workload without compromising safety or acute success. Although its discrimination for late recurrence is modest, it offers practical value for procedural planning and operator guidance in fluoroless AFL ablation.C.I