Effect of Isthmus Anatomy and Ablation Catheter on Radiofrequency Catheter Ablation of the Cavotricuspid Isthmus

Abstract

Background-Cavotricuspid isthmus (CTI) characteristics are rarely documented when comparing catheters in radiofrequency ablation (RFA) of atrial flutter (AFL). Our objectives were (1) to evaluate the impact of CTI morphology and length on ablation procedures and (2) to compare the efficacy of an 8-mm-tip catheter with an irrigated cooled-tip RFA in the subgroup presumed to be more difficult to treat (with a long CTI, Ͼ35 mm). Methods and Results-Over a period of 17 months, 185 patients accepted the protocol and underwent an isthmogram in preparation for RFA. Groups were classified according to CTI length and CTI morphology. RFA was performed with an 8-mm-tip catheter for patients with a short CTI, Յ35 mm (nϭ123), whereas randomization between an 8-mm-tip and a cooled-tip catheter applied to patients with a longer CTI, Ͼ35 mm (nϭ62). For long CTI, 32 patients were assigned to an 8-mm catheter and 30 patients to the cooled-tip RFA ablation group. In this subset, RF application (18.2Ϯ17 versus 19Ϯ13 minutes) and x-ray exposure (20.8Ϯ18 versus 18Ϯ13 minutes) did not differ between the 8-mm-tip and the cooled-tip procedures. Number of applications (9.9Ϯ11 versus 18.6Ϯ15 minutes; PϽ0.0001) and x-ray exposure (11.7Ϯ11 versus 19.5Ϯ16 minutes, Pϭ0.0001) differed significantly between patients with short and long CTIs.Patients with short and straight CTIs required 3 times fewer RFA applications and shorter x-ray exposure compared with other CTI morphologies (pouch-like recesses and concave characteristics). Conclusions-The number of RF applications required for a complete isthmus block in long CTIs is not influenced by the choice between an 8-mm or cooled-tip catheter. Procedure parameters, however, are significantly influenced by CTI length and morphology. Pouch-like recesses and concave characteristics account for much longer ablation times at all

Reduction in Atrial Flutter Ablation Time by Targeting Maximum Voltage: Results of a Prospective Randomized Clinical Trial

“…Although bidirectional conduction block across the isthmus effectively eliminates symptoms in a large majority of patients, 1,2 rare treatment failures are often ascribed to discontinuity in the ablation line 3 . A purely anatomically delivered contiguous line of lesions across the isthmus can be challenging to create, resulting in long procedural and ablation times 4–12 . Pathology studies have shown the CTI, in most cases, to be composed of discrete bundles of muscle with intervening connective tissue, 13 suggesting that a contiguous line of ablation may not be necessary to achieve bidirectional conduction block.…”

Radio-Frequency Ablation of Atrial Flutter: Long-Term Results and Predictive Value of Cavo-Tricuspid Isthmus Bidirectional Block as Determined by a Simplified Technique

“…We could not achieve complete CTI bidirectional block in 16% of patients, which is the failure rate usually reported when using standard techniques (0–25% [3, 15,17,18,19, 22,34,35,36,37,38,39,40]). Excessive CTI thickness, existing pouches, recesses or trabeculations, local edema, or catheter instability during AF, are the suspected causes of failure.…”

Temporal Pattern of Conduction Recurrence During Radiofrequency Ablation for Typical Atrial Flutter

“…Undoubtedly, collateral functional conduction block exists adjacent to the zone of thermal necrosis and no current diagnostic technology including most sophisticated imaging or recording techniques is capable of distinguishing between irreversible thermal damage and transient stunning of the tissue. Common atrial flutter ablation typically requires series of high‐power RF deliveries including cooled ablation in order to destroy sometimes bulky or anatomically complex CTI 14–16 . In the case of cooled‐tip technology, the situation may paradoxically complicate even more.…”