Catheter Ablation Therapy for Atrial Fibrillation

Ablation of atrial fibrillation: comparison of catheter-based techniques and the Cox-Maze III operation

BACKGROUND

Catheter-based ablation is often recommended for treatment of atrial fibrillation (AF), but there are no data that directly compare late results to those of the Cox-Maze procedure. Although catheter ablation avoids operation, lack of reliable transmurality may reduce effectiveness. We compared clinical outcomes of the cut-and-sew Cox-Maze procedure with catheter ablation.

METHODS

Between January 1993 and October 2007, 97 patients aged 25 to 80 years underwent an isolated cut-and-sew Cox-Maze procedure. Patients were matched 1:2 according to age, sex, and AF type, with 194 patients undergoing catheter-based ablation for lone AF.

RESULTS

At last follow-up, 82% of patients who underwent the Cox-Maze procedure were free of AF and had stopped taking antiarrhythmic medications compared with 55% of patients who underwent ablation (p<0.001). When analyzed as a time-related event, freedom from recurrent AF was 87% 5 years after the Cox-Maze procedure compared with 28% after catheter ablation (p<0.001). Late warfarin anticoagulation was required in 12% of patients who underwent the Cox-Maze procedure compared with 55% of patients who underwent ablation (p<0.001), and use of antiarrhythmic medications during follow-up was significantly higher in patients who underwent ablation (68% versus 15%, p<0.001). Forty-one patients (24%) required repeated ablation procedure and 9 required a second repeated ablation.

CONCLUSIONS

Compared with catheter-based ablation, the Cox-Maze procedure results in greater freedom from AF and less medical treatment with antiarrhythmic drugs and warfarin anticoagulation during follow-up.

Evaluating the left atrium by magnetic resonance imaging

The emergence of catheter based ablation therapy for the prevention of recurrent atrial fibrillation has increased interest in the anatomy of the left atrium and pulmonary veins. In this article, we review the magnetic resonance imaging method of imaging the left atrium and the pulmonary veins, normal and variant anatomy, and the utility of imaging before and after atrial fibrillation ablation.

Preventive ablation strategies in a biophysical model of atrial fibrillation based on realistic anatomical data

Ablation strategies to prevent episodes of paroxysmal atrial fibrillation (AF) have been subject to many clinical studies. The issues mainly concern pattern and transmurality of the lesions. This paper investigates ten different ablation strategies on a multilayered 3-D anatomical model of the atria with respect to 23 different setups of AF initiation in a biophysical computer model. There were 495 simulations carried out showing that circumferential lesions around the pulmonary veins (PVs) yield the highest success rate if at least two additional linear lesions are carried out. The findings compare with clinical studies as well as with other computer simulations. The anatomy and the setup of ectopic beats play an important role in the initiation and maintenance of AF as well as the resulting therapy. The computer model presented in this paper is a suitable tool to investigate different ablation strategies. By including individual patient anatomy and electrophysiological measurement, the model could be parameterized to yield an effective tool for future investigation of tailored ablation strategies and their effects on atrial fibrillation.

Pulmonary vein region ablation in experimental vagal atrial fibrillation: role of pulmonary veins versus autonomic ganglia

BACKGROUND

Pulmonary vein (PV) -encircling radiofrequency ablation frequently is effective in vagal atrial fibrillation (AF), and there is evidence that PVs may be particularly prone to cholinergically induced arrhythmia mechanisms. However, PV ablation procedures also can affect intracardiac autonomic ganglia. The present study examined the relative role of PVs versus peri-PV autonomic ganglia in an experimental vagal AF model.

METHODS AND RESULTS

Cholinergic AF was studied under carbachol infusion in coronary perfused canine left atrial PV preparations in vitro and with cervical vagal stimulation in vivo. Carbachol caused dose-dependent AF promotion in vitro, which was not affected by excision of all PVs. Sustained AF could be induced easily in all dogs during vagal nerve stimulation in vivo both before and after isolation of all PVs with encircling lesions created by a bipolar radiofrequency ablation clamp device. PV elimination had no effect on atrial effective refractory period or its responses to cholinergic stimulation. Autonomic ganglia were identified by bradycardic and/or tachycardic responses to high-frequency subthreshold local stimulation. Ablation of the autonomic ganglia overlying all PV ostia suppressed the effective refractory period-abbreviating and AF-promoting effects of cervical vagal stimulation, whereas ablation of only left- or right-sided PV ostial ganglia failed to suppress AF. Dominant-frequency analysis suggested that the success of ablation in suppressing vagal AF depended on the elimination of high-frequency driver regions.

CONCLUSIONS

Intact PVs are not needed for maintenance of experimental cholinergic AF. Ablation of the autonomic ganglia at the base of the PVs suppresses vagal responses and may contribute to the effectiveness of PV-directed ablation procedures in vagal AF.

Surgical approaches for atrial fibrillation

The Cox Maze procedure, a cardiac intervention that was developed by James Cox, MD, was first performed in 1988 to surgically cure atrial fibrillation. Over the years, changes in techniques of the classic maze were made, culminating in the Cox Maze III procedure, the Gold Standard. Modifications in the original procedure included simplifying the procedure to a minimally invasive approach. As a result of some of these modifications, the initial maze-like series of surgical atrial incisions has been reduced with the use of alternate energy sources that create hyperthermic lesion lines of conduction block that isolate and interrupt the abnormal impulses. The minimize, a minimally invasive thorascopic approach, can be performed off pump, thus avoiding a median sternotomy and cardiopulmonary bypass and cardioplegic arrest intraoperatively and ensuring a shorter, less painful recovery.

The ambiguous pulmonary venoatrial junction: a new perspective

PURPOSE

The pulmonary venoatrial junction (PVAJ) has recently received attention due to the widespread use of catheter ablation for atrial fibrillation. However, the literature lacks a consensus in the definition of the PVAJ. We aim to review the inconsistent definitions for the PVAJ and related implications in imaging and catheter ablation for atrial fibrillation.

RESULTS

The PVAJ as described by embryology, gross anatomy, histology and imaging is ambiguous, leading to disparities in its definition. Because of differing definitions of the PVAJ, there is a broad range in the prevalence of anatomic variations, including (1) percentage of common pulmonary veins (10-79% on the left), (2) supernumerary pulmonary veins (10-42%) and (3) ostial diameter and shape. We postulate several reasons for this broad range in the described prevalence of anatomic variation of the PV as follows: (1) different definitions of the PVAJ, (2) different vantage points, (3) different imaging modalities, and (4) different prevalence of anatomic variants among different study populations.

CONCLUSIONS

The ambiguous PVAJ with its gradual transition from the left atrium to the pulmonary veins defies precise definition even though it plays an important role in the management of atrial fibrillation. Physicians should be aware of variability in the language used to describe the PVAJ and resultant discrepancy in reported anatomical information.

Cerebral air embolization in the Electrophysiology Laboratory during Transseptal Catheterization: Curative treatment of acute left hemiparesis with prompt hyperbaric oxygen therapy

We present a case of a 44 year-old man with medically refractory symptomatic paroxysmal atrial fibrillation in whom the initial attempt at left atrial catheter ablation was complicated by coronary and cerebral arterial air embolization during transseptal catheter exchange. The manifestations, management, and long term outcomes are detailed. Following the case report is a review of published reports and contemporary management strategies for treatment of acute air embolization. Dramatic clinical consequences can be aborted by prompt intervention including volume loading, oxygenation, lidocaine, and hyperbaric oxygen therapy.

Is Helicobacter pylori a cause of atrial fibrillation?

Inflammation has been implicated in the pathogenesis of cardiovascular diseases. C-reactive protein, a sensitive marker of systemic inflammation, has recently been reported to be significantly higher in patients with atrial fibrillation (AF) compared with a control group with no history of atrial arrhythmia. Elevated C-reactive protein levels in patients with AF reflects an underlying inflammatory process. Histological anomalies in the atria of patients with AF have also been observed. These anomalies may have an inflammatory basis, although it is not known if any structural changes within the atria are a cause or a consequence of the arrhythmia. Ongoing chronic infection(s) has been suggested as a possible cause of the inflammatory process demonstrated in patients with AF. Helicobacter pylori, a Gram-negative bacterium more commonly known for infecting the gastric mucosa and causing peptic ulcers, is a noncardiac factor that has been controversially reported to be associated with cardiovascular diseases. This article gives a brief overview of AF and specifically explores the recent evidence that suggests that Helicobacter pylori infection causes AF.