Imaging Study
LVOT gradient was measured via transthoracic echocardiograph under
resting conditions before the procedure and at 1, 3, and 6 months post
procedure during follow-up. Other variables measured included maximal
interventricular septum (IVS) thickness, left atrial (LA) diameter and
anterior mitral valve leaflet (AML) length. LVOT obstruction due to
systolic anterior motion of the mitral valve (SAM) was determined by the
highest gradient acquired with continues wave Doppler in the apical
three-chamber (or five-chamber) view. The length of the AML was measured
in diastole on the apical three-chamber view.15Considering the severity of symptoms and significant gradient, stress
echocardiography was not performed.
Cardiac magnetic resonance imaging (CMR) was performed in 10 patients
before ablation. Considering the change of LV morphology was
minor,9 11 CMR was performed in other 6 patients after
6 months follow up. Distribution of hypertrophic segments was assessed
using 16-segment model.16 Average septal thickness
measurements in each of the 16 segments were automatically calculated
with commercially available software. (Figure 1) At the 3 LV levels
(i.e. basal, mid, and apical), the number of hypertrophied segments in
septum (≥15 mm) was recorded as well as the papillary muscle (PM)
abnormalities.