Catheter ablation
Ablations were performed under general anesthesia with low tidal volume
ventilation and uninterrupted anticoagulation. Three dimensional
guidance was performed with the CARTO 3 system (Biosense Webster).
Heparin infusion was utilized to maintain an activated clotting time of
350 seconds. Pacing from either the coronary sinus (CS) or right
ventricle was performed to reduce the stroke volume and variability in
cardiac motion. All procedures utilized irrigated radiofrequency with
the STSF catheter aiming for interlesion distances of 4mm (Biosense
Webster). In addition to VOM ethanol infusion, the standard lesion set
for patients with persistent AF in this study consisted of PVI, left
atrial posterior wall isolation (PWI), CS isolation, posterior mitral
isthmus line (MIL), and a cavotricuspid isthmus line (CTI) (Figure 1).
The mitral isthmus was ablated with air-filled balloon occlusion of the
CS in almost all cases to improve lesion transmurality near the
annulus.7 In the subset
of patients both with persistent and occasionally paroxysmal AF wherein
VOM ethanol was not preplanned and rather performed ad hoc (most
commonly for induced mitral annular flutter in patients with myopathic
low voltage regions, Table 1), MIL, CS isolation, and PWI was still
systematically performed. The sought end points for CS isolation and PWI
included elimination of local electrograms and lack of pace capture of
the atrium with high output bipolar pacing from within the isolated
structure (20mA, 2msec). The proximal third of the CS was not ablated to
avoid iatrogenic atrioventricular (AV) block. For the first half of the
enrollment period, luminal temperature monitoring was used for
esophageal protection and occasionally, PWI was avoided in favor of a
reinforced roof line if the esophageal risk was deemed too great because
of esophageal heating or close proximity to the posterior wall on
intracardiac echo (ICE). Towards the latter half of the study, patients
underwent active esophageal cooling at 4°C (Enso ETM, Attune Medical,
Chicago, IL). Rarely, CTI ablation was avoided if typical atrial flutter
was not inducible and the appearance of the region on ICE appeared
anatomically challenging. Adenosine was used to assess for dormant
conduction and in select procedures, isoproterenol infusion was used to
disclose non-PV foci.