Anatomical obstacles in cavotricuspid isthmus detected by modified 2D transthoracic echocardiography and long-term outcomes in radiofrequency ablation of typical atrial flutter.

Abstract

Background: Although radiofrequency ablation of the cavotricuspid isthmus (CTI), responsible for sustaining atrial flutter, is a highly effective procedure, in extended patient observations following this procedure, more than 10% becomeunsuccessful. Therefore, this study was aimed at providing helpful information about the anatomy of the CTI in transthoracic echocardiography, which could aid better planning of CTI radiofrequency ablation in patients with typical atrial flutter.

Materials and methods: 56 patients with typical atrial flutter after radiofrequency ablation were evaluated at the end of a 24-month observation period. With substernal modified transthoracic echocardiographic (mTTE) evaluation, we identified four main anatomical obstacles impeding radiofrequency ablation: tricuspid annular plane systolic excursion, cavotricuspid isthmus length, cavotricuspid isthmus morphology, and the presence of a prominent Eustachian ridge/Eustachian valve. All intraprocedural radiofrequency ablation data was collected for analysis and correlated with anatomical data.

Results: Over a 24-month observation period, freedom from atrial flutter was 67.86%. The mean length of the isthmus was 30.34 ± 6.67 mm. The isthmus morphology in the 56 patients was categorised as flat (n = 27; 48.2%), concave (n = 10; 17.85%), or pouch (n = 19, 33.9%). A prominent Eustachian ridge was observed in 23 patients (41.1%). Lack of anatomical obstacles in mTTE evaluation resulted in 100% efficacy, while the presence of at least two obstacles significantly increased the risk of unsuccessful ablation with more than two (OR 12.31 p = 0.01). Generally, 8 mm electrodes were the most effective for non-difficult CTI, while 3.5 mm electrodes used with a 3D system had highest performance forcomplex CTI. Notably, ageing was the only factor that worsened the long-term outcome (OR 1.07 p = 0.044).

Conclusions: Preoperative use of mTTE evaluation helps predict difficulty in cavotricuspid isthmus radiofrequency ablation, thus allowing better planning of the radiofrequency ablation strategy using the most accurate radiofrequency ablation electrode.