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.