Left Ventricular Torsion Reflects Degree Of Myocardial Fibrosis In Hypertrophic Cardiomyopathy

Background : LV torsion (LVtor) is reduced in patients with impaired LV systolic function, e.g., dilated cardiomyophaty. It used to be thought that LVtor is reduced in patients with hypertrophic caridiomyopathy (HCM) because of the myocardial disarray; however, recent observation showed that LVtor assessed with tagged magnetic resonance imaging (MRI) even increased in patients with HCM. Recently LVtor is assessable with novel ultrasound speckle tracking imaging (STI) method. This technique may be used to assess intra-ventricular torsion in the LV muscle (intra-LVtor) that occurs due to the different fiber directions between the endocardium and epicardium. In this study, we analyzed LVtor and intra-LVtor in light of LV fibrosis in patients with HCM. Methods : MRI and echo studies were performed in 10 patients with HCM in whom any medication had not been given to HCM. MRI was used to determine LV mass index. In addition, %DEmass was determined as an MRI index of the extent of myocardial fibrosis by dividing the extent of late gadolinium enhancement by LV mass. We acquired basal and apical short-axis LV images with 2D echocardiography for off-line STI analysis to determine LVtor and intra-LVtor. We traced 18 points of the endcardium and epicardium, respectively, and averaged all regional rotation at the basal and apical plane, respectively. LVtor was defined as the difference of LV rotation between the basal and apical plane. Intra-LVtor was defined as the difference in the rotation between the endcardium and epicardium. Results : There was a significant correlation between %DEmass and LVtor(r=−0.72, p<0.05, indicating that LVtor is reduced in HCM patients with larger extent of LV myocardial fibrosis. There was no significant correlation between LVtor and LV mass index (r=−0.15, p=n.s.). %DEmass also correlated with intra-LVtor (r=−0.67, p<0.05, indicating that intra-LVtor is reduced in HCM patients with larger extent of LV myocardial fibrosis. Conclusions : Both LV torsion and intra-LV torsion are reduced in HCM patients with extended LV fibrosis. In other words, the extent of myocardial fibrosis may be assessed with LVtor and intra-LVtor by use of speckle tracking imaging in patients with HCM.