Study Traces Origins of Recurrent VT Following Ablation

New research is helping unravel the causes of recurrent ventricular tachycardia (VT) in patients who have already undergone catheter ablation for VT following myocardial infarction.

A new study published on Oct. 31 in the Journal of the American College of Cardiology found that the primary reason for VT recurrence "was the occurrence of new VTs that were most often mapped to sites adjacent to scar from prior ablation lesions or areas that were initially not thought to contain VT circuits." In addition, patients with VT recurrence had more extensive scarring than patients without recurrent VT.

The study followed 98 patients for a mean of 35 months following catheter ablation to treat post-infarction VT. All patients had failed to respond to antiarrhythmic drugs before ablation. All inducible VTs were targeted for ablation using radiofrequency energy at critical sites of the VT re-entry circuit. Critical sites were identified with pace-mapping, and ablation was targeted at either the VT isthmus for tolerated VT or clustered around areas of good pace-maps for poorly tolerated VT.

According to the study authors, there was no recurrent VT in 63 percent of patients following ablation. Of the 33 patients with recurrent VT, 14 underwent repeat ablation for a total success rate of 77 percent. Researchers found that the most common origin for recurrent VT following ablation is adjacent to prior ablation lesions (53 percent). The second most common origin is a new region not identified in the original ablation session (32 percent).

"Patients with recurrent VTs have a larger scar as assessed by electroanatomic mapping," said lead author Miki Yokokawa, MD, research fellow at the University of Michigan Health System, Ann Arbor, MI. "Complete linear lesions are difficult to achieve in the ventricle, yet complete linear lesions may be one way to reduce VT recurrence post-ablation. Real-time intraoperative magnetic resonance imaging may help to assure that ablation lesions are complete."

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In an accompanying editorial, Edward Gerstenfeld, MD, FACC, chief of Cardiac Electrophysiology and Arrhythmia at the University of California San Francisco Medical Center, said the study authors should be congratulated for providing new information about VT recurrence after ablation. "Maintaining the intracardiac electrograms for all the clinical and induced VTs, maintaining a uniform stimulation protocol and maintaining detailed enough maps over seven years such that a comparison of VT isthmus location was possible for patients undergoing repeat ablation represents a truly Herculean effort," he said.

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