Ablation of atrial fibrillation

Abstract

Ablation is increasingly used to treat AF, since recent trials of pharmacological therapy for AF have been disappointing. Ablation has been shown to improve maintenance of sinus rhythm compared to pharmacological therapy in many multicenter trials, although success rates remain suboptimal. This review will discuss several trends in the field of catheter ablation, including studies to advance our understanding of AF mechanisms in different patient populations, innovations in detecting and classifying AF, use of this information to improve strategies for ablation, technical innovations that have improved the ease and safety of ablation, and novel approaches to surgical therapy and imaging. These trends are likely to further improve results from AF ablation in coming years as it becomes an increasingly important therapeutic option for many patients.

Figure 1. Meta-analysis of single procedure success rates from AF ablation

(A) in paroxysmal and non-paroxysmal AF by study (see reference for details) (B) Higher success for paroxysmal than non-paroxysmal AF, but with considerable overlap. Multiple procedure success rates are higher.

Figure 2. Trends in Mechanism-Based AF Ablation Sets

(A) Triggers initiate AF, then increasingly well-defined mechanisms sustain AF (with permission from Calkins, et al. (12). (B) Conventional ablation lines are designed to isolate triggers (PV isolation), empirically target other potential mechanisms, or (C) target localized regions, all predominantly in the left atrium (with permission from Calkins, et al. (12). (D, E) Actual ablation lesions for PVI combined with ablation of ganglionic plexus sites (with permission from Katritsis, et al. (53). There are trends for patient-specific mechanism-targeted ablation in both atria. (F) Focal Impulse and Rotor map showing bi-atrial mechanisms sustaining AF in a specific patient, including a right atrial rotor and a left atrial focal driver, and (G) actual lesions delivered at RA rotor (LA lesions of similar area, out of plane in this view) (with permission from Narayan et al. (59).

Figure 3. Technical Advances in AF Ablation

(A) Typical fluoroscopy showing a circular mapping catheter, a decapolar catheter in the coronary sinus and an ablation catheter. Using fluoroscopy alone is technically challenging when moving in a 3D structure. An improvement is the addition of (B) Rotational angiography, in which a 3D representation of patient anatomy is generated at the time of ablation using X-ray images acquired during a contrast injection. (C) Electro-anatomic mapping showing catheters. In this image, the Velocity system (St Jude Medical, Sylmar, California) uses catheter impedance within the chamber to depict atrial contours and catheter location (in this case, 64 pole basket catheters for FIRM-guided ablation). An imaging trend is to display more than just atrial anatomy. (D) Electro-anatomic mapping showing ablation lesions. In this image, the CARTO system (Biosense-Webster, Diamond Bar, California) shows left atrial geometry, catheters and user-defined parameters for lesion formation plotted onto the shell. In this instance, lesions are automatically placed on the shell only when a pre-specified force, catheter stability and impedance drop have been achieved. (E) The Convergent Procedure. Due to prolonged ablation time and poorer outcomes of catheter ablation in patients with longstanding persistent AF, this hybrid procedure was developed in which the surgeon enters the pericardium via the diaphragm to ablate almost all of the posterior left and right atria. The electrophysiologist then ensures PVI with additional ablation. Results have been promising in small series.

Figure 4. Trends for the In-hospital complications from AF ablation

using the Nationwide Inpatient Sample in 93, 801 procedures in the U.S. from 2000 to 2010. Complication rates were lower in higher volume centers (see text) (With permission from Deshmukh et al. (5).