Background-Blood flow near a radiofrequency (RF) lesion can reduce lesion size by convective cooling. It is unknown whether blood flow through small vasculature within an RF lesion can prevent transmural lesion formation. Methods and Results-In 40 rabbit right ventricle preparations, 2 epicardial RF lesions were created straddling a selectively perfused (0 to 12 mL/min) marginal artery (diameter, 0.34Ϯ0.1 mm). RF lesions were created at either 60°C or 80°C and delivered either sequentially or simultaneously. Conduction through the lesion area was measured. The lesions were analyzed histologically. At a perfusion rate of 0 mL/min, all RF lesions were transmural and without conduction. As little as 1 mL of flow through the artery during RF delivery could prevent transmural lesion formation by preserving a cuff of tissue along the length of the vessel. High-energy delivery (45 W) and very high tissue temperatures (93°C) were needed to overcome the protective effect of vascular perfusion at 12 mL/min. The volume of preserved myocardium was related to arterial perfusion rate, artery diameter, and lesion temperature but not to the sequence of RF delivery (sequential versus simultaneous). Conduction persisted through the RF lesion in 20 experiments. Conduction through the lesion was related to the arterial perfusion rate and volume or cross-sectional area of preserved myocardium. Conclusions-Flow through even small intramyocardial vessels can prevent transmural lesion formation and preserve conduction through an RF lesion. These findings may represent an unrecognized obstacle to the creation of linear RF lesions in the clinical setting.

Acutely following RF energy delivery, APD, APDmax, and CT are reduced in the tissue surrounding the lesion. These electrophysiologic changes resolve within 22 +/- 13 days of lesion formation.

The aim of the study was to determine the long-term freedom from atrial arrhythmias after radiofrequency ablation of atrial flutter and to determine the factors associated with recurrent arrhythmias. Radiofrequency ablation has emerged as the preferred treatment for recurrent, typical atrial flutter. Although the short-term results after radiofrequency ablation of atrial flutter have been widely reported, there is insufficient data on long-term outcome with respect to the occurrence of atrial arrhythmias in patients after successful ablation. The first 108 patients to undergo successful ablation for typical atrial flutter at the authors' institutions were followed prospectively until the occurrence of typical atrial flutter, atrial fibrillation, atypical atrial flutter, or death. Several prespecified clinical and procedural factors were tested using univariate and multivariate analysis as predictors of arrhythmia recurrence. Patients were followed for a minimum of 3 years and a maximum of 8 years, or until the first arrhythmia recurrence (average duration 17 +/- 17 months). Recurrences of typical atrial flutter were usually observed within the first 6 months (73%, n = 16), with the remainder (27%, n = 6) occurring between 6 months and 2 years, and none were observed later. Freedom from recurrence of typical atrial flutter was 80% at 1 year (95% CIs 72-89%), 73% at 2 years (CIs 63-83%), and 73% at 5 years (CIs 63-83%). By contrast, freedom from occurrence of atrial fibrillation or atypical atrial flutter progressively declined over time; 80% at 1 year (CIs 71-88%), 59% at 2 years (CIs 48-70%), and 33% at 5 years (CIs 19-48%). A history of atrial fibrillation or atypical atrial flutter prior to ablation was associated with an increased risk of occurrence during follow-up (relative risk 3.4, CIs 1.5-8.1, P < 0.05). Freedom from occurrence of any atrial arrhythmia was only 27% at 5 years (CIs 15-40%). After successful ablation of typical atrial flutter, recurrence of typical flutter is relatively uncommon and usually occurs early. However, there is a progressive occurrence of atrial fibrillation and/or atypical flutter during follow-up so that many patients require further antiarrhythmic or additional ablative therapy. Radiofrequency ablation of typical atrial flutter should be considered a palliative procedure for most patients and only one component of the long-term care of the patient with atrial tachyarrhythmias.