The Myocardial Strain And Fibrosis Analysis In Myocardial Hypertrophy By Cardiac Magnetic Resonance

Objective: To investigate the effect of myocardial strain and myocardial fibrosis on left ventricular function from pathophysiology and histological level in patients with hypertrophic cardiomyopathy(HCM)and hypertensive heart disease(HHD).Methods: Patients with HHD and HCM,as well as age-matched healthy controls were prospectively enrolled.Cardiac echocardiography and cardiac magnetic resonance imaging were performed on each patient in different group.Stratified myocardial strain analysis(inner and outer)was performed on cine,a balanced,steady state,free precession sequence(SSFP),and myocardial fibrosis and scar analysis were performed on T1 mapping and gadolinium contrast-enhanced delayed imaging(LGE).Results: In the analysis of myocardial strain,in the equivalent level of left ventricular mass(HHD: 201 ± 100 g vs.HCM: 212 ± 75 g,P> 0.05;P < 0.001),patients with HCM displayed hyperdynamic contraction compared to HHD and healthy control(Control: 70 ± 9% vs.HHD: 65 ± 12% vs.HCM: 76 ± 10%,P <0.001).Longitudinal strain was lower in both HCM and HHD,including that in the global and stratified layers,compared with controls(P<0.001).Regarding the global circumferential strain(GCS),however,the deformation trend differed between HHD and HCM primarily in the endocardium,which presented with increased myocardial deformation in HCM(-35.63± 5.30% vs.-32.84± 7.04% in controls,P= 0.03),whereas no such movement diversity was observed in the sub-endocardium or sub-epicardium.In addition,linear regression analyses showed a moderate correlation between global circumferential strain and left ventricular ejection fraction(LVEF)(r =-0.48 and r =-0.499);moreover,the inner layers(endocardium and sub-endocardium)had a stronger correlation with LVEF than the outer layers(epicardium and sub-epicardium)(r=-0.511 for subendocardium vs.-0.422 for subepicardium;-0.485 for endocardium vs.-0.404 for epicardium).Notably,in contrast to HHD,endocardial circumferential strain remained “higher” in HCM patients when the LVEF was below normal(-35.08± 8.35%,P=0.046).In the analysis of myocardial fibrosis,it was also found that the myocardial mass of this two different cardiomyopathies were at the equivalent level(HHD: 180.7 g vs.HCM: 201.9 g,P> 0.05;P <0.001 for both groups compared to the control group(100.2 g)).HCM patients also displayed a hyperdynamic myocardial contractility compared with control group and HHD patients(Control: 65.6% vs.HHD: 66.13% vs.HCM: 76.1%,P <0.001).Interestingly,patients with HCM prone to suffer from focal fibrosis,while patients with HHD mostly displayed diffuse fibrosis;moreover,HCM patients could result in higher rate of LGE-positive(HCM: 84% vs.HHD: 34%,P< 0.001)and more myocardial scar compared to HHD(HCM:(2.21-15.1)% vs.HHD:(0-0.94)%,P< 0.001).Even in patients with normal diastolic function,the HCM groups had a higher ECV(25± 2% in the HCM group and 24± 2% in the control group,p=0.03).Regarding the patients with moderate-to-severe diastolic dysfunction,a similar extent of an elevated ECV(HCM: 29± 4% vs.H-LVH: 30± 2%;P= 0.59)was associated with a higher percentage of patients in the HCM group(30% of the patients in the HCM group vs.16% in the HHD group,p=0.04;LV mass/volume ratio 1.33–2.30 in the HCM group,1.18–1.66 in the HHD group and 0.65–0.97 in the control group,p<0.001).Conclusion:1.Distinct peak strain deformation was found between HCM and HHD patients with the similar cardiac hypertrophy and an equivalent increase in ECV 2.Strain distinction was observed in the circumferential but not longitudinal direction.3.Peak circumferential strain moderately correlated with LVEF.GCS of endocardial myocardium was preserved in patients with HCM even with a reduced left ventricular ejection fraction(LVEF),which reflects a better preservation of endocardial contractility.4.The associations between native ECV and LV functional parameters were distinct in the HCM and HHD groups.Elevated ECV was associated with increased myocardial stiffness and severely impaired diastolic function in patients with HCM,and associated with the decompensation of LVEF in patients with HHD.