INVESTIGATION OF POTENTIAL CAUSES OF PULMONARY VEIN RECONNECTION AND OF STRATEGIES TO IMPROVE EFFICACY AND SAFETY OF PULMONARY VEIN ISOLATION FOR ATRIAL FIBRILLATION ABLATION

Due to the increasing prevalence and the associated cardiovascular mortality and morbidity, atrial fibrillation (AF) represents a major burden on healthcare. Catheter ablation is currently the most effective rhythm control strategy available for patients with AF. However, its long-term efficacy is suboptimal, and it carries risks of serious complications. This work investigated potential causes of radiofrequency (RF) ablation failure, translating into pulmonary vein reconnection (PVR) after an acutely successful isolation, and strategies to improve ablation efficacy and safety. In 54 patients, the impact of a continuous oesophageal temperature monitoring - guided ablation strategy (premature cessation of energy delivery in case of oesophageal temperature rise >39°C) on PVR was assessed. No correlation was found between occurrence of temperature alerts and reconnection in the associated pulmonary vein. In a randomised study on 80 patients, use of different RF powers on the left atrial (LA) posterior wall was compared on risk of oesophageal heating and clinical procedure success. High power/short duration ablation was associated with similar rate of oesophageal temperature alerts and lower long-term AF recurrence rate than lower power/longer duration ablation. A subsequent analysis on 44 patients investigated the relation between Lesion Size Index (LSI) and tissue impedance drop, as traditional marker of lesion formation. For any LSI value, use of higher powers translated to progressively higher impedance drops after shorter ablation durations. Catheter stability and contact force played a more relevant role on impedance drop when using lower powers. Various target LSI values corresponding to maximum impedance drop were identified depending on ablation settings used. Finally, intracardiac echocardiography (ICE) and intravascular ultrasound (IVUS) were explored for measurement of LA wall thickness at the ablation sites in 12 patients. Both techniques were feasible, however ICE showed higher imaging quality and inter- observer reproducibility than IVUS. Acute wall thickening suggestive of oedema was observed after RF and laser treatment but not after cryoablation