RESUMEN
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 (obstructive HCM [HOCM] group) and those with LVOTPG < 30 mmHg (HNCM group). The echocardiographic morphological variables were analyzed to determine whether they were predictive of LVOT obstruction. Systolic anterior motions of the mitral valve were observed in 100% of patients in the HOCM group but only in 58% in the HNCM group. 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 inter-ventricular septum (5.97 ± 2.3 versus 9.20 ± 1.9 mm, respectively, P < 0.0001) and a longer anterior mitral leaflet (AML) length (24.7 ± 5.8 versus 20.1 ± 5.4 mm, respectively, P < 0.01) compared to the HNCM group. The AML length/LVDs ratio was significantly higher in the HOCM group compared to the HNCM group (1.02 ± 0.34 versus 0.78 ± 0.26, P < 0.01), and an LVOT obstruction was predicted with an area under the curve of 0.71 (P < 0.05). Multiple linear regression revealed that only the AML length/LVDs ratio was independently associated with LVOTPG (P < 0.01).The AML length/LVDs ratio has a 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.