Radiofrequency Ablation of Atrial Flutter
A33-year-old man with cardiac and pulmonary sarcoidosis developed ventricular tachycardia managed with an implantable cardioverter-defibrillator and amiodarone therapy. Subsequently, episodes of atrial flutter triggered spurious therapies from the implantable cardioverter-defibrillator, and the patient underwent electrophysiological evaluation. Common atrial flutter (caudocranial septal and counterclockwise right atrial activation) was induced, with a cycle length of 270 ms. Entrainment with a postpacing interval equal to the flutter cycle length was demonstrated in the right atrial inferior isthmus (Figure 1A⇓), indicating that this region was part of the macroreentrant circuit. A steerable 7F quadripolar 4-mm-tip thermistor radiofrequency (RF) ablation catheter (EP Technologies, Inc) was used to make a line of RF lesions extending from the tricuspid annulus to the inferior vena cava until bidirectional isthmus conduction block could be demonstrated. Atrial flutter ended during RF current application (Figure 1B⇓). Subsequently, there was no recurrence of atrial flutter. However, progressive heart failure and frequent episodes of ventricular tachycardia continued, and heart transplantation was performed 3 weeks after RF ablation of atrial flutter. The explanted heart was examined after removal. A diaphragmatic view of the heart illustrates the relationship of the right atrial inferior isthmus with the coronary vessels (Figure 2⇓). A longitudinal section of the right AV groove is seen in Figure 3A⇓. RF lesions extended to depths up to 2 mm, whereas the distance from the endocardial surface at the ablation site to the right coronary artery is 4 mm. Microscopically, the RF lesions were characterized by coagulation necrosis with hemorrhage surrounded by a rim of granulation tissue (Figure 3B⇓).
Ablation of atrial flutter has been established to be a safe procedure. Despite the proximity of the right coronary artery, no arterial damage has been reported thus far. To some extent, the arteries are protected by luminal blood flow, which serves as a heat sink, keeping the vessel wall cool when surrounding tissue is heated. However, with advances in technology, ablation catheters capable of creating larger and deeper lesions are entering clinical trials. The images in the present report showing proximity of the right coronary artery to the region targeted for ablation of common atrial flutter suggest that ablation systems capable of making deeper lesions require cautious evaluation if they are to be applied to ablation of atrial flutter.
Dr Delacretaz was supported by grants from the Swiss National Science Foundation and from the Swiss Foundation for Grants in Medicine and Biology.
The editor of Images in Cardiovascular Medicine is Hugh A. McAllister, Jr, MD, Chief, Department of Pathology, St Luke’s Episcopal Hospital and Texas Heart Institute, and Clinical Professor of Pathology, University of Texas Medical School and Baylor College of Medicine.
Circulation encourages readers to submit cardiovascular images to Dr Hugh A. McAllister, Jr, St Luke’s Episcopal Hospital and Texas Heart Institute, 6720 Bertner Ave, MC1-267, Houston, TX 77030.
- Copyright © 1999 by American Heart Association