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.