Electrophysiology Study and Ablation
Data collection and analysis were performed according to protocols approved by the NYU Langone Health Institutional Review Board. Surface and intracardiac electrograms (ECGs) were digitally recorded and stored (EP Workmate, Abbott Medical, Inc.,). Non-fluoroscopic 3-dimensional mapping was performed using the Carto 3 (Biosense-Webster, Inc.,) mapping system.
All procedures were performed under general anesthesia with standard mechanical ventilation using weight-based tidal volumes. A 7-French 20-pole catheter (Daig DuoDeca 2-10-2, Abbott Medical, Inc.) was used with the distal poles placed within the coronary sinus and the proximal electrodes located along the tricuspid annulus in the lateral and inferior right atrium. For left atrial mapping and recording, a 10- or 20-pole circumferential PV mapping catheter (Lasso, Biosense-Webster, Inc.), or a five-spline mapping catheter (PentaRay Nav, Biosense-Webster, Inc.) was utilized. Left atrial three-dimensional anatomy and voltage mapping was created with manipulation of the multi-electrode mapping catheter. Low-voltage areas were defined as bipolar voltage <0.5 mV either during AF or atrial pacing.
Ablation was performed in each group with an open-irrigated, 3.5-mm RFA catheter (ThermoCool SmartTouch, Biosense Webster Inc.). Ablation lesions were generated in a power-controlled mode applying 20 to 35 W for 20 to 40 seconds per lesion during irrigation at a rate of 17 to 30-mL/min while maintaining a goal ACT of > 350 seconds. All electroanatomic map lesion markers were created using automated lesion annotation (VisiTag, Biosense Webster, Inc.) with settings at the discretion of each operator.
A stepwise linear ablation approach, as previously described by O’Neill et al, 10 was utilized in Group 1. PVAI was performed as the initial step with wide area circumferential lesions created approximately 1 cm proximal to the ostium of each of the right veins and posterior left veins. When AF terminated during this step, entrance and exit block was assessed with the ablation catheter during sinus rhythm and confirmed with a multielectrode mapping catheter at the end of the procedure as described below. If AF persisted, only entrance block was confirmed and additional linear ablation was performed. The second step was ablation along the LA roof creating a line between the isolated left and right pulmonary veins at approximately the 12 o’clock (superior) position. The next step was targeting complex LA activity while the patient remained in AF, which included regions of continuous electrical activity, complex fractionated atrial electrograms, and locally short cycle lengths. These regions included the posterior interatrial septum, posterior LA, base of LAA, inferior LA, coronary sinus, anterior LA, and mitral isthmus at the discretion of the operator. The goal of ablation in each of these regions was to organize local activity, decrease amplitude of atrial signals, and to achieve a line of block when a mitral line was created. When electrogram-based ablation of the LA did not result in organization of the coronary sinus, electrogram-based ablation was performed in the right atrium (RA) if the RA appendage demonstrated a shorter cycle length than the LA appendage targeting areas of complex electrograms in the RA. If the patient remained in atrial fibrillation, decision to perform electrical cardioversion due to procedure length or extensive atrial ablation was at the discretion of the operator. LA PWI was utilized in Group 2, which included PVAI, as described above, followed by isolation of the LA posterior wall. PWI was achieved by creating linear lesions along the posterior LA roof and posterior-inferior LA between the isolated pulmonary veins.
If the patient converted to an atrial tachycardia in either group, the arrhythmia was mapped and targeted with ablation. Ablation of the CTI was performed at the discretion of the operator in both groups. A waiting period of 30 minutes, followed by administration of adenosine, was utilized to confirm entrance and exit block. If prior ablation sites were still excitable with bipolar pacing output of 10 mA at 2 msec after PVAI or LA PWI, additional ablation lesions were delivered until loss of pace capture was achieved at that location. 11,12 All sites of adenosine elicited dormant PV or LA posterior wall conduction were also ablated.