Use of intracardiac echocardiography during atrial fibrillation ablation.

As the volume and complexity of catheter ablation of atrial fibrillation (AF) continue to rise, there is increasing attention directed at reducing exposure to ionizing radiation. This has led to the emergence of intracardiac echocardiography (ICE) as a stand-alone imaging modality guiding AF ablation. In addition to directing transseptal puncture, ICE may be used to identify left atrial structures and to guide the manipulation of catheters. ICE may also be used to visualize the esophagus in real-time and to assist with early identification of procedural complications. This review provides detailed step-by-step directions for identification of relevant structures and summarizes the use of ICE during AF ablation.

Electromagnetic interference complicating Impella® use during pediatric ablation.

In children, the Impella® is most commonly used in the setting of cardiogenic shock. There are few reported cases of Impella® use in pediatric patients undergoing ablation; description of troubleshooting techniques may improve success rates. We describe a pediatric patient with tachycardia-induced cardiomyopathy due to incessant ectopic atrial tachycardia whose ablation was notable for significant electromagnetic interference (EMI) from the Impella® leading to incomplete mapping. This case highlights the need for multidisciplinary planning and consideration of possible EMI with the use of magnet-based electroanatomic mapping systems as well as troubleshooting techniques to reduce the impact of EMI.

Prospective study of atrial fibrillation termination during ablation guided by automated detection of fractionated electrograms.

INTRODUCTION: Complex fractionated atrial electrograms (CFAE) may identify critical sites for perpetuation of atrial fibrillation (AF) and provide useful targets for ablation. Current assessment of CFAE is subjective; automated detection algorithms may improve reproducibility, but their utility in guiding ablation has not been tested. METHODS AND RESULTS: In 67 patients presenting for initial AF ablation (42 paroxysmal, 25 persistent), LA and CS mapping were performed during induced or spontaneous AF. CFAE were identified by an online automated computer algorithm and displayed on electroanatomical maps. A mean of 28 +/- 18 sites/patient were identified (20 +/- 13% of mapped sites), and were more frequent during persistent AF. CFAE occurred most commonly within the CS, on the atrial septum, and around the pulmonary veins. Ablation initially targeting CFAE terminated AF in 88% of paroxysmal AF, but only 20% of persistent AF (P < 0.001). Subsequently, additional ablation was performed in all patients (PV isolation for paroxysmal AF, PV isolation + mitral and roof lines for persistent AF). Minimum follow-up was 1 year. One-year freedom from recurrent atrial arrhythmias without antiarrhythmic drug therapy after a single procedure was 90% for paroxysmal AF, and 68% for persistent AF. CONCLUSIONS: Ablation guided by automated detection of CFAE proved feasible, and was associated with a high AF termination rate in paroxysmal, but not persistent AF. As an adjunct to conventional techniques, it was associated with excellent long-term single procedure outcomes in both groups. Criteria for identifying optimal CFAE sites for ablation, and selection of patients most likely to benefit, require additional study.

Surface electrocardiographic patterns and electrophysiologic characteristics of atrial flutter following modified radiofrequency MAZE procedures.

INTRODUCTION: The radiofrequency MAZE is becoming a common adjunct to cardiac surgery in patients with atrial fibrillation. While a variety of postoperative arrhythmias have been described following the original Cox-MAZE III procedure, the electrophysiological characteristics and surgical substrate of post-radiofrequency MAZE flutter have not been correlated. We sought to determine the location, ECG patterns, and electrophysiological characteristics of post-radiofrequency MAZE atrial flutter. METHODS: Nine consecutive patients with post-radiofrequency MAZE flutter presented for catheter ablation 9 +/- 10 months after surgery. RESULTS: Only one patient (11%) had an ECG appearance consistent with typical isthmus-dependent right atrial (RA) flutter. However, on electrophysiological study, 3/9 patients (33%) had typical right counter-clockwise flutter entrained from the cavo-tricuspid isthmus, despite description of surgical isthmus ablation. Six patients (67%) had left atrial (LA) circuits. These involved the mitral annulus in 5/6 cases (83%) despite description of surgical mitral isthmus ablation in the majority (60%). LA flutters had a shorter cycle length compared with RA flutters (253 +/- 39 msec and 332 +/- 63 msec respectively, P < 0.05). After a mean of 8 +/- 4 months following ablation, 8/9 patients (89%) were in sinus rhythm. CONCLUSION: Up to one-third of post-radiofrequency MAZE circuits are typical isthmus-dependent RA flutters, despite a highly atypical surface ECG morphology. Therefore, diagnostic electrophysiological studies should commence with entrainment at the cavo-tricuspid isthmus in order to exclude typical flutter, regardless of the surface ECG appearance. Incomplete surgical lesions at the mitral and cavo-tricuspid isthmus likely predispose to the development of post-radiofrequency MAZE flutter.

Electroanatomic mapping of postpacing intervals clarifies the complete active circuit and variants in atrial flutter.

BACKGROUND: Typical atrial flutter is characterized by cavotricuspid isthmus dependence and activation sequentially around the tricuspid annulus (TA), usually counterclockwise. However, analysis of the upper portion of the annulus by postpacing interval after entrainment sometimes suggests it is outside the circuit. Details on the true active circuit are limited, particularly in the upper portions. OBJECTIVE: The purpose of this study was to define the full active circuit in atrial flutter. METHODS: In 26 patients with isthmus-dependent atrial flutter, we created detailed electroanatomic maps of postpacing intervals throughout the entire right atrium. Postpacing intervals within 20 ms of the flutter cycle length were defined as within the circuit. RESULTS: Creating postpacing interval maps allowed characterization of the full active circuit in all patients, and revealed significant variations despite similar counterclockwise or clockwise patterns with activation mapping. In 8, the active circuit was solely around the TA. In 14, an oblique course between the anterior and posterior borders was found, with the upper circuit off the annulus, posterior to the right atrial appendage base. Of these, 8 coursed anterior to the SVC, 5 behind the SVC and 1 bifurcated the SVC. In 4 others, bifurcation of the upper circuit was seen around the right atrial appendage (n = 3), or around the combined right atrial appendage-superior vena cava (n = 1). CONCLUSION: Despite similar activation around the TA, creating electroanatomic postpacing interval maps distinguishes the active flutter circuit from passively activated myocardium. Significant variability exists in the active circuit, with only a minority around the TA. Most commonly, the circuit courses not around a single barrier but obliquely between anterior and posterior borders.