Catheter Ablation of Ventricular Tachycardia Associated with Hypertrophic Cardiomyopathy: Substrate Characterization and Ablation Outcome According to Clinical Subtypes.

概要

Catheter ablation is a therapeutic option to suppress ventricular tachycardia (VT) in patients
with hypertrophic cardiomyopathy (HCM) inadequately controlled by antiarrhythmic medications.
As a natural course of HCM, some patients developed thin-walled apical aneurysm (AA), while
on the other hand, some patients eventually progressed to the end-stage phase with left ventricular
(LV) dysfunction named dilated phase HCM (DHCM). There is no study that evaluated catheter
ablation of VT and determined the location and distribution of the VT substrate as endocardial or
epicardial/intramural according to the clinical HCM subtypes, which is the aim of this study.
Method
Thirty HCM patients (17 patients with HCM and AA and 13 patients with DHCM) with
sustained monomorphic VT (65± 11 years, 26 (87%) male) were retrospectively included in this
study. All the ablation procedures were performed using 3D electroanatomic mapping. The VT
substrate was organized into 17 segments according to the American Heart Association Model for
unified assessment. The patients were followed after catheter ablation through regular outpatient
visits or by remote device monitoring for evaluation of VT recurrence. The comparison for
significance between the two groups was done by using t-test, Mann-Whitney test, or chi-square
test accordingly. The VT free event was analyzed using Kaplan-Meier survival curve and Log
Rank test for significance.
Result
The LV ejection fraction was significantly lower in patients with DHCM than those with HCM
and AA (39 ± 9% vs 60 ± 11%, respectively: P˂ 0.0001), reflecting LV dysfunction in patients
with DHCM. None of the DHCM patients had normal QRS morphology and duration in the
baseline rhythm, while 41% of HCM with AA patients had normal QRS (P= 0.008). The axis of
the targeted clinical VT was also different as being mainly inferiorly directed in DHCM compared
to superiorly directed in HCM with AA, indicating the site of origin whether basal or apical sites,
respectively. The patients with DHCM underwent 23 procedures compared to 20 procedures in
HCM with AA group reflecting the difficulty to suppress VTs in DHCM. As the VT substrate was
in the AA in most HCM with AA group (16 of 17 patients) and close to the endocardial surface so
the endocardial ablation sufficiently suppresses the VTs in HCM with AA in most patients.
However, as the VT substrate in DHCM was in the basal epicardial/intramural location mainly in
the antero-septum, targeting these sites were challenging despite using different ablation strategies.
This was reflected in the VT recurrence during the follow-up period. While 10 (77%) of 13 patients
in HCM with AA group were free of VT recurrence after single endocardial ablation, 5 (45.5%)
of 11 patients with DHCM were free of VT recurrence. ...

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