Safety and outcomes of ablation
The presence of a mechanical mitral valve for VA ablation can pose
unique operative risks. Strict attention with respect to periprocedural
anticoagulation is required to minimize the risk of thromboembolism or
valve thrombosis. In addition, meticulous care is required when mapping
around the valve to avoid catheter entrapment. We typically avoid use of
a multispline 37 catheter in patients with mechanical
valves due to the risk of entrapment and device shearing. In addition,
use of ICE is strongly encouraged to help more accurately determine
anatomical locality. In addition, fluoroscopic imaging in the right
anterior oblique plane would help provide information regarding
proximity to the mitral valve. In the rare and potential catastrophic
event of catheter entrapment during mapping or ablation, management
includes cautious catheter rotation/ manipulation in various planes to
free up the catheter. Advancement of a support sheath up to the level of
obstruction can be entertained. Furthermore, measures to prolong mitral
valve opening such as rapid ventricular pacing and adenosine (which
prolong diastole) can be attempted.38 If these
measures fail, one can employ extraction techniques or ultimately
consider surgical removal.
Thromboembolic events are uncommon, yet devastating complication of VT
ablation. Ventricular ablation is associated with an inherent risk of
thrombus formation with thrombus size directly proportional to ablative
lesion size.39 Reported incidence of stroke/ TIA with
VT ablation ranges from 0.8% to 1.8%.40,41 Studies
have shown that the incidence of thromboembolic events with VT ablation
is higher in patients with structural heart disease.42In our study, no thromboembolic events or other procedure-related
complications were reported. ICE was performed before and after the
ablation did not detect any change of valve function or development of
pericardial effusion. Ecktar et al reported a series of VT ablation in
20 patients including 8 patients with MVS.10 In their
study, during a median follow-up of 2.1 years, 11(55%) patients
remained free of spontaneous VT. Three patients had repeat ablation due
to recurrent VT. In our study, the overall VA recurrence-free rate at
1-year was 13/18 (72.2%). We also found that MVS patients with a
history of CAD showed a trend of better VA recurrence-free survival
compared with those without CAD history. (Figure 2B ) This could
be related to the previously reported different nature of VT circuits
between ICM and NICM. 43,44 One observational study
compared the characteristics and the outcomes of VT ablation between ICM
and NICM patients has shown that complete success and 1-year VT-free
survival were higher in the ICM group.44 The critical
isthmus for VT was identified with endocardial entrainment in 62% of
the ICM group and in 17% of the NICM group. The lower likelihood of
identifying the isthmus in NICM might be related to a midmyocardial or
epicardial location, which is a less amenable location for successful
ablation especially in patients with previous cardiac surgery.