RADIOFREQUENCY ABLATION OF CAVOTRICUSPID ISTHMUS: IS THE CLINICAL TYPE OF ATRIAL FLUTTER IMPORTANT?

To study peculiar features of radiofrequency ablation (RFA) of cavotricuspid isthmus (CTI) in patients with paroxysmal, persistent, and permanent atrial flutter (AFL), 197 patients aged 55.7±11.1 years (129 men; 65.5%) were examined and surgically treated. The patients with paroxysmal AFL (61.4%) constituted Group I and the subjects with persistent (14.7%) and permanent AFL (23.9%), Group II. Before the surgical treatment, ECG was recorded, transthoracic echocardiography (EchoCG) and duplex scanning of brachiocephalic arteries were performed, as well as coronary angiography (when indicated). Arterial hypertension was documented in 47% of patients; in one third of patients, Type I AFL was associated with paroxysmal atrial fibrillation (AF). The intracardiac electrophysiological study was performed to all patients. RFA of CTI was carried out according to the standard technique: consecutive radiofrequency applications were made from the tricuspid valve ring towards the lower cave vein. Used were non-irrigated 8 mm Blazer II catheters (Boston Scientific, USA) with the following parameters: temperature: 60°C., power: 70 W. When indicated, the power was increased to 80 W and a switch was performed to the irrigated ablation using the ExSteer or Celsius Thermocool catheters (Biosense Webster, Israel) in the following ablative regime: temperature: 43°C., power: 40 W. The total procedure duration was 85 min (60 110 min), the fluoroscopy time: 30 min (23 41 min), the total dose: 712 Gy (578 930 Gy), and the skin exposure: 8,064 mGy^xm2 (6,210 10,230 mGy^xm2). The effectiveness criteria were achieved in 85.3% of procedures. The recurrence of typical AFL 3 months after the operation, which required an additional intervention, was documented in 8 patients (4%). 24 hour ECG monitoring was indicated in 15 patients due to pronounced sinus bradycardia after the sinus rhythm recovery (80%) or transient/complete atrio-ventricular (AV) block during radiofrequency application on the medial isthmus (20%). In the course of RFA of CTI during paroxysms of AFL (n=105; 53%), the sinus rhythm recovered in 66 subjects (63%). If AFL did not terminate during the ablative procedure, the overdrive anterograde pacing was performed. In 54.5% of cases, electric cardioversion was necessary to restore the sinus rhythm. In the patients of both groups, RFA on the sinus rhythm was shorter: the overall duration of the procedure was 75 min (55 105 min) whereas, at the background of AFL, it was 90 min (70 120 min). The RFA effectiveness was 88% in patients on the sinus rhythm and 83.8% in other patients (p=0.1). In Group I, the most frequent finding was the bidirectional isthmus-block (88.4%), whereas it occurred only in 80.3% of cases in Group II. It was verified in 93% of subjects with the normal atrial size and only in 82.6% of subjects with the dilated right atrium (p=0.1). Thus, a longer duration of the procedure in the patients with persistent/permanent AFL is caused by an increased atrial size, which is developed in the course of the arrhythmia perpetuation. The obtained data regarding a lower effectiveness of the procedure in chronic forms of AFL are limited by the small sample of the study.

typical atrial flutter, cavotricuspid isthmus, intracardiac electrophysiological study, radiofrequency ablation, remodeling

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