Ann Arbor, MI - A new study investigating the feasibility of a tailored ablation strategy has shown that an approach targeting only the initiators and drivers of atrial fibrillation (AF) can reduce recurrence rates [1]. During a median follow-up of 11 months, 77% of patients were free from recurrent AF, but more important, investigators say unnecessary applications of radiofrequency energy can be avoided with the tailored approach, thereby minimizing the risk of atrioesophageal injury.

"A variety of mechanisms may play a role in the genesis of AF, and different mechanisms may be operative in different patients," write lead investigator Dr Hakan Oral (University of Michigan, Ann Arbor) and colleagues in the April 19, 2006 issue of Circulation. "With the use of a tailored ablation strategy, it may be possible to identify and eliminate the specific mechanism(s) of AF and at the same time minimize risk to the esophagus."

Catheter ablation of atrial fibrillation typically targets the pulmonary-vein region of the posterior left atrium. Although the procedure is considered safe, reports of esophageal damage, perforation, and atrioesophageal fistulas after radiofrequency ablation have surfaced in the literature. Because of the proximity of the esophagus to the posterior wall of the left atrium, radiofrequency ablation procedures can elevate temperatures within the lumen of the esophagus, resulting in thermal injury and possible necrosis.

In an attempt to minimize these risks, Oral and colleagues suggest that a tailored catheter ablation strategy guided by the electrophysiological characteristics of AF could eliminate the rhythm disorder without the use of a standard lesion set. The group contends that as the drivers and initiators of AF vary from patient to patient, it is possible to identify the specific generators of AF by mapping the pulmonary veins, left atrium, coronary sinus, and superior vena cava and then specifically ablating these problematic sources.

In total, 153 consecutive patients with symptomatic, paroxysmal AF underwent a left atrial ablation procedure, the end point of which was the termination and noninducibility of AF. The pulmonary veins and left atrium were mapped during spontaneous or induced AF. In total, the right-sided pulmonary veins were encircled in 15 patients, the left-sided pulmonary veins encircled in five patients, and both the right-sided and left-sided pulmonary veins encircled in 50 patients. After elimination of the pulmonary vein tachycardia, if AF was still present or inducible, identified complex electrocardiograms were targeted for ablation.

During follow-up, left atrial flutter developed in 19% of patients and was present in 10% of the subjects at 12 weeks. A repeat ablation procedure was performed in 28 patients, of whom 20 had recurrent AF. During the repeat ablation procedure in these patients with recurrent AF, arrhythmogenic activity in the pulmonary veins not initially targeted was identified in 12 patients.

In terms of freedom from recurrent AF and atrial flutter, investigators report that after a median follow-up of 11 months after the last ablation procedure, 118 of the 153 patients (77%) were free from recurrent AF or flutter in the absence of antiarrhythmic drug therapy.

Oral and colleagues suggest that the tailored approach avoids unnecessary applications of radiofrequency energy. Because noninducibility is the procedural end point—achieved in 58% of the 153 patients—ablation is no longer continued once AF terminates and is noninducible. This differs from pulmonary vein isolation or circumferential pulmonary vein ablation, where energy is applied until the lesion sets are complete. In addition to reducing the amount of energy applied, the tailored approach seeks to identify mechanisms of AF not within the pulmonary veins or included in encircling lesions during ablation, the authors add.

Commenting on the results of the Oral et al study for heartwire, Dr Peter Gallagher (Central Baptist Hospital Heart Institute, Lexington, KY) said the approach appears to present a logical roadmap for difficult paroxysmal AF ablation cases, especially as clinicians try to minimize the risk of injury to patients.

"It comes up a lot of times where you're ablating and you're seeing increases in the esophageal temperature, and you're questioning whether you really need to ablate there," said Gallagher. "This study would say that you might not need to. You can focus your attention perhaps on other locations instead. You can shift your attention to some of these other more tailored locations, giving a better success rate with less risk to the patient."

Gallagher suggests that the tailored approach to ablating AF is feasible and notes that some clinicians are likely doing some form of tailored ablation in their practice.

"I would suspect that most clinicians who have done atrial-fibrillation ablations have done some form of empiric isolation and some form of tailored ablation, particularly if there is an apparent repetitive source of ectopy or a repetitive source of where the atrial fibrillation is coming from," said Gallagher. "We tend to target that and go after it. What this study has done is to elegantly combine ablation of both the suspected initiators and possible perpetuators of atrial fibrillation in these patients."

Limiting the amount of radiofrequency ablation is important for reducing the risk of esophageal damage, perforation, and atrioesophageal fistula, but Gallagher noted there have also been reports in the literature of gastric hypomotility. In some patients, the vagus nerve runs between the esophagus and atrium and can be injured during ablation. Although the tailored approach is time-consuming, running between three and four hours in the report by Oral and colleagues, the results may change the way a lot of people think about isolating the pulmonary veins, said Gallagher.