Characteristics of the VT group (Table 3)
The median duration between valve surgery and VT onset was 4.0 (IQR 0.3,
12.1) years while the median duration between MVS and VT ablation was
5.0 (IQR 1.0, 11.0) years. Twelve patients in this group had MV repair
while 4 patients had MV replacement (of which 1 had a mechanical valve).
Seventy percent of the VT group had ICD in situ prior to ablation, the
rest had ICD implantation after the ablation. Of the 16 patients in this
group, 13 patients (81%) had failed ≥1 AAD, 11 (85%) of whom had
failed a Class III AAD prior to ablation. The median LVEF was 28 (IQR
20, 36). The mean LVEDD was66 ±9 mm. The mean RVSP was42 ±16 mmHg.
General anesthesia was used in 7 (40%) patients. Thirty-seven VTs were
induced with a median of 2 (IQR 1, 3). Seventy percent of induced VTs
had RBBB morphology with superior axis being the predominant axis.
Thirty percent of induced VTs had LBBB morphology where the origin of VT
was found to be RV, interventricular septal, or mitral isthmus. The
median VT cycle length was 378 (IQR 298, 477) ms. Scar-related reentry
was the major mechanism of induced VTs. Only one patient had BBR VT
which occurred following a complicated aortic valve replacement surgery.
Substrate mapping demonstrated heterogenous scar that involved the
perimitral valve area in 8 (50%) patients. Despite that, the site of
successful ablation included the perimitral region only in 6 patients.
Procedural success was achieved in 94% of the VT group. Only one
patient had procedural failure. This patient had an EF of 20% with a
history of NICM and prior VT ablation. During ablation, induced VTs were
associated with hemodynamic instability requiring multiple
defibrillations and the use of a percutaneous left ventricular assist
device. The critical isthmus was felt to be epicardial.
The median total procedure time for the VT group was 298.5 (IQR 414.8,
226.5) minutes and median fluoroscopy time was 35.65 (IQR 52.0, 26.1)
minutes. The median energy delivery time was 64.0 (IQR 95.3, 34.7)
minutes. Following the procedure, all patients in the VT group were
continued on their preprocedural AAD regimen.