Morphological Determinants of Obstructive Hypertrophic Cardiomyopathy Obtained Using Echocardiography

The morphological determinants of left ventricular outflow tract (LVOT) obstruction in hypertrophic cardiomyopathy (HCM) are not completely understood. We aimed to identify the anatomical risks of the obstruction using echocardiography. Fifty patients with untreated HCM were classified into two groups: those with LVOT pressure gradient (LVOTPG) > 30 mmHg (HOCM group, n = 17) and those with LVOTPG < 30 mmHg (HNCM group, n = 33). There were no significant differences in wall thickness, end-systolic LV dimension (LVDs), or LVOT diameter between the two groups. However, HOCM subjects had a shorter distance from papillary muscles to the interventricular septum (5.97 ± 2.3 vs. 9.20 ± 1.9 mm, respectively, P < .0001) and a longer anterior mitral leaflet (AML) length (24.7 ± 5.8 vs. 20.1 ± 5.4 mm, respectively, P < .01) than those in the HNCM group. The AML length/LVDs ratio was significantly higher in the HOCM group compared to the HNCM group (1.02 ± 0.34 vs. 0.78 ± 0.26, P < .01), and predicted LVOT obstruction with an area under the curve of 0.71 (P < .05). Multiple linear regression revealed that only the AML length/LVDs ratio was independently associated with LVOTPG (P < .01). The AML length/LVDs ratio has significant predictive value for LVOT obstruction and a strong relationship with LVOTPGs. The AML length/LVDs ratio determines the anatomical risk of LVOT obstruction in HCM.