BOSTON — A tailored approach to catheter ablation of atrial fibrillation is better than using a standard lesion set in all patients.
The basic tenets underlying a tailored strategy are that all atrial fibrillation is not the same, the less ablation the better, and a “one size fits all” approach would mean that some patients get more ablation than they need and others don't get enough, Dr. Fred Morady said at an international symposium on atrial fibrillation sponsored by Massachusetts General Hospital.
Other important rationales for an individualized approach to catheter ablation is that it's possible to identify the important triggers and drivers of atrial fibrillation in each patient, and that the end point of treatment in the electrophysiology lab is to treat until fibrillation is no longer inducible and no longer triggered by a dose of isoproterenol. Also, individualized treatment can help reduce ablations near the esophagus and thereby avoid damage that can lead to fistula formation, said Dr. Morady, professor of internal medicine and director of the clinical electrophysiology laboratory at the University of Michigan, Ann Arbor.
The algorithm that Dr. Morady and his associates use starts with inducing atrial fibrillation in the electrophysiology lab, using isoproterenol if needed. He also has the patient swallow a barium solution so the esophagus can be visualized during the procedure.
The obvious place to start assessing fibrillation triggers is to map the pulmonary veins with a lasso catheter and isolate any culprit pulmonary veins. If the fibrillation persists, the next step is to hunt for complex electrograms, either rapid or fractionated. These might be in the left atrial roof or septum, the coronary sinus, the superior vena cava, or the right atrium.
In patients with paroxysmal fibrillation, the end point for ablation is no spontaneous fibrillation, and no inducible fibrillations that last more than a minute after five attempted inductions. For patients with chronic fibrillation, the goal is to eliminate any pulmonary vein triggers and to ablate all ECG-guided culprit sites. “A limited amount of ablation can have a dramatic effect,” Dr. Morady said at the symposium, also sponsored by the Academy for Healthcare Education.
Dr. Morady and his associates have used the tailored approach to treat 153 patients since they began the strategy in 2004. At least one pulmonary vein trigger was found in every patient. In addition, complex ECGs were seen in the left atrium in 69% of patients, in the coronary sinus in 46%, and in the superior vena cava in 6%. (Some patients had more than one complex ECG.)
The average time for each procedure was 201 minutes, and the average time spent ablating trigger sites was 32 minutes. Fibrillation was rendered uninducible in 58%. Left atrial flutter occurred in 19%, although this later resolved in half of these patients. Repeat ablations were performed in 18% of patients.
Among the patients who were uninducible after treatment, 88% remained free from fibrillations after an average follow-up of 11 months. Among those who remained inducible, new fibrillation episodes occurred in 35% during follow-up. About two-thirds of the patients had chronic atrial fibrillation, and in this subgroup the fibrillation was terminated and sinus rhythm was restored in 54%.
For patients with chronic atrial fibrillation, 'a limited amount of ablation can have a dramatic effect.' DR. MORADY