Electrophysiology Study and Ablation
Patients were taken to the electrophysiology laboratory in the fasting,
postabsorptive state. The level of anesthesia was determined by the
performing electrophysiologist. Intravenous prophylactic antibiotics
were administered. Following vascular access, intravenous heparin was
administered to achieve activated clotting time (ACT) of 300-350
seconds. An arterial line was placed for continuous blood pressure
monitoring. A 5 French (Fr) quadripolar catheter was placed in the right
ventricular apex and a 7 Fr decapolar catheter was placed in the
coronary sinus. Intracardiac echocardiography (ICE, Acuson, Siemens,
Germany) was used as standard to assist mapping/ ablation and assess for
complications. Left ventricular (LV) access was obtained by anterograde
trans-septal or retrograde trans-aortic approach. 3-dimensional
electroanatomical mapping (CARTO, Biosense Webster, Diamond Bar, CA) was
used in all patients. Mapping was performed in point-by-point fashion
using an externally irrigated ablation catheter (THERMOCOOL® Biosense
Webster, Diamond Bar, CA). For VTs, programmed ventricular stimulation
and burst pacing were utilized for induction. For PVCs, burst pacing was
favored if PVCs were scarce. Isoproterenol was utilized as needed for
both. Standard mapping techniques were used to identify ablation
targets.17 In the case of PVCs, activation and pace
mapping was predominantly utilized. In VT cases, entrainment and
activation mapping were used if the arrhythmia was hemodynamically
tolerated. With unstable VT, pace and substrate mapping were favored.
Scar-related reentry was defined as the VT mechanism when VT was
inducible with programmed stimulation and when entrainment could be
demonstrated. VT was considered involving the perimitral area in cases
where abnormal electrograms and critical sites responsible for VT were
identified within 2 cm of the valve annulus. Ablation energy was
typically started at 30 W and up-titrated as necessary, up to a maximum
limit of 50 W.