Hypertrophic cardiomyopathies (HCM) are often associated with left ventricular (LV) outflow tract obstruction, which can explain symptoms. The aim of our work was to study the relation between LV obstruction and LV shape.

36 patients with HCM who underwent cardiac magnetic resonance imaging (CMR) were retrospectively included. Clinical diagnosis of HCM was based on the demonstration by bi-dimensional trans-thoracic echocardography (TTE) of a hypertrophied and nondilated LV (wall thickness >15mm) in the absence of another disease capable of producing a similar degree of hypertrophy. Obstructive HCM was defined by a LV outflow gradient >30mmHg at rest. LV shape and mitral angle were assessed by CMR. Tricuspid - mitral angle (TMA) and LV - mitral angle (LVMA) were defined by the angle between the tricuspid annulus and the mitral annulus, and the angle between the LV axis and the mitral annulus in the 4-chamber view respectively. Mitral papillary muscles angle (MPMA) was defined by the angle between both mitral papillary muscles and the center of the LV in the LV short axis view. There were 20 (56%) men and the mean age was 55±14. There were 24 (67%) patients with obstructive HCM with a mean LV outflow tract gradient of 90(46mmHg. TMA, LVMA and MPMA were smaller in obstructive HCM patients than in non-obstructive HCM patients (7±3 versus 11±4°, p<0.001; 79±5 versus 87±7°, p=0.007 and 126±14 versus 140±13°(, p=0.015 respectively). In the overall population, there was a negative linear relationship between the peak instantaneous LV outflow tract gradient at rest and TMA, LVMA and MPMA with a R² value of 0.2 (p=0.04), 0.2 (p=0.02) and 0.3 (p=0.04) respectively.

LV obstruction is negatively correlated with mitral annulus angle with the LV and inter-mitral papillary muscles space. These results confirm the relationship between LV obstruction and LV shape in HCM.