Abstract 3354: Posterior Mitral Leaflet/Left Ventricular Cavity ‘Mismatch’ is an Important Factor for Development of Systolic Anterior Motion of Mitral Valve Among Patients With Hypertrophic Cardiomyopathy
Introduction: The venturi effect, flow drag effect and abnormal mitral valve apparatus have all been implicated in the development of systolic anterior motion (SAM) of mitral valve among HCM patients. Nevertheless, SAM has also been shown to occur in the absence of HCM or abnormal mitral apparatus. A long posterior mitral leaflet (PML) in relation to the LV cavity may move the coaptation point of the leaflets anteriorly during systole, thus exposing the PML/AML to the flow drag effect of the ejecting blood.
Hypothesis: We hypothesize that a simple ‘mismatch’ between PML length and LV cavity i.e. a high PML/LV internal diameter in systole (LVIDS) ratio is an important factor for SAM of mitral valve to occur in HCM patient. The null hypothesis is there was no difference in the PML/LVIDS ratio among HCM patients, with or without SAM.
Methods: Consecutive 74 patients who were diagnosed to have HCM with asymmetrical septal hypertrophy(ASH) from our echocardiography laboratories from November 2007 to November 2008 were retrospectively included in this study. Offline cine-loop reviewed and measurement made in parasternal long axis view: PML length in diastole, LVIDS, maximal septal thickness, presence/absence of SAM and maximal left ventricular outflow tract (LVOT) gradient if SAM was present (any view).
Results: The mean age of our patients was 59±32 years old. SAM of mitral valve occurred in 28 them (37%). Comparing the groups with SAM and no SAM, there were no differences in age and maximal septal thickness (mean 2.38±0.94 cm vs. 2.28±0.92 cm respectively, p>0.05). However, the PML/LVIDS ratio was significantly higher in the SAM group (mean 0.85±0.42 vs. 0.52±0.22 in no SAM group, p<0.0001). The PML was also significantly longer in SAM group (mean 1.63±0.70 cm vs. 1.24±0.52 cm for no SAM group, p<0.001). No relationship existed between the ratio and maximal LVOT gradient.
Conclusions: A significantly higher PML/LVIDS ratio was observed in HCM patients with ASH who had SAM of mitral valve. The null hypothesis is rejected. A simple PML and LV cavity mismatch might have contributed to the occurrence of SAM in this group of patients.