25Invasive transseptal assessment of posterior wall isolation >4yrs post surgical AF ablation in stable sinus rhythm and recurrent af patients. is isolation required for success?

Abstract

Introduction: There are many different lesion sets that are used for the surgical ablation of atrial fibrillation (AF). One such pattern is the ‘box set’, a single ring of scar delivered anterior to the pulmonary veins, which aims to isolate the posterior wall from the rest of the heart. However it remains unclear whether posterior wall isolation (PWI) is required for maintenance of sinus rhythm. We investigated the long-term integrity of the ‘box set’ lesion created during surgical AF ablation by epicardial High Intensity Focussed Ultrasound (HIFU). All patients had documented persistent or recurrent paroxysmal AF prior to surgery. We correlated this with subsequent success or failure in the abolition of atrial fibrillation. Methods: With regional ethical and R&D approval, we recruited 16 patients, 10 with ongoing AF and 6 in normal sinus rhythm, who had previously undergone HIFU AF ablation: 14 during concomitant cardiac surgery and 2 stand alone ablation. Clinical history and 7-day holter was used to define the NSR group. We performed a diagnostic EP study using a transseptal approach in fully anticoagulated patients (INR > 2.0 and ACT maintained at >350s). A catheter was placed in the coronary sinus (CS) and a circular multipolar mapping catheter was used to map the left atrium and pulmonary veins. Patients in atrial fibrillation were cardioverted. We recorded whether posterior wall and pulmonary vein isolation (PWI + PVI) had been achieved at the surgical procedure. In selected cases we recorded a voltage map (EnSite™ Velocity™, St. Jude Medical, UK) to identify areas of ablation scar (see Figure 1). Results: All 10 patients with ongoing AF had absence of PWI + PVI with electrograms recorded across the PW. In the 6 patients with long-term confirmed sinus rhythm, PWI + PVI was confirmed in 4 (67%) and in 2 there was prolonged conduction across the box-set lesion with CS to PW activation time of around 200ms versus 45ms from CS to left atrial appendage. Of the 4 patients with confirmed PWI + PVI, 1 had dissociated spontaneous atrial potentials within the box set area and the other 3 had electrical silence with inability to capture the posterior wall pacing at 10mA at multiple sites Conclusions: There appears to be a clear correlation between the successful restoration of long-term sinus rhythm and isolation / delayed conduction from the pulmonary veins and posterior wall. Given the advent of hybrid atrial fibrillation ablation techniques designed to deliver this lesion set, these findings are of great significance. ![Graphic][1] Figure 1 Voltage map from EnSite™ Velovity™ with box-set lesion shown in red (arrow) [1]: /embed/inline-graphic-1.gif