Study On The Mechanisms And Influencing Factors Of SAM In Hypertrophic Obstructive Cardiomyopathy

The mechanisms of systolic anterior motion(SAM)of the mitral valve in hypertrophic obstructive cardiomyopathy(HOCM)remain unclear.The influencing factors of SAM have also been being explored.This article mainly did some attempts about the mechanisms and influencing factors of SAM.In order to investigate the impact of the angle of attack between blood flow and mitral valve leaflets on SAM at the pre-SAM time point,patient-specific CT-based computational models were constructed for 5 patients receiving septal myectomy surgery to obtain pre-and post-operative 2D vector flow mapping.We compared the pre-and post-operative angles of attack based on 2D vector flow mapping of 5 patients.The results showed that there was no statistically significant difference between pre-and post-operative angles of attack(61.1±14.4°vs.56.2±8.0°,p=0.306,n=5).Therefore,we proposed that the angle of attack might not play an important role in the initiation of SAM.To investigate the effect of the space between the coaptation and the septum in the early systole on the occurrence of SAM,we measured the cross-sectional area of the outflow tract and the left ventricle in the left ventricular short-axis sections at the coaptation level of 20 patients based on their echocardiography.The ratio(R)=area of the outflow tract/area of the left ventricle was used to represent the space between the coaptation and the septum.It was found that the post-operative ratio(R)increased significantly(0.265±0.050vs.0.320±0.081,p=0.007,n=20).So we proposed that the space between the septum and the coaptation in the early systole was a key factor influencing the occurrence of SAM.Our results indicate that when performing septal myectomy(Morrow procedure),the focus should be on the septal region opposite the mitral valve;in order to eliminate the SAM,the resection range and depth of this region should be as large as possible.