The Study Of Left Ventricular Myocardial Work In Patients With Nonobstructive Hypertrophic Cardiomyopathy By Non-invasive Myocardial Work Index

Background Hypertrophic cardiomyopathy(HCM)is an autosomal dominant genetic disease,which is characterized by unexplained ventricular hypertrophy.The pathological mechanism is mutation of gene map encoding sarcomere protein,abnormal hypertrophy of myocardial cells,disorder of myocardial fiber arrangement and interstitial fibrosis,which leads to systolic and diastolic dysfunction of left ventricle,which is the main cause of sudden cardiac death for teenagers and athletes.The clinical manifestations of HCM patients are lack of specificity,mainly manifested as laboring dyspnea,fatigue and chest pain,and the disease progress is slow.Syncope is the first cause of diagnosis in some patients,and the prognosis of different patients is quite different.Persistent atrial fibrillation,heart failure and sudden cardiac death are the main causes of death,and there is still no radical cure at present.Most patients often have no obvious clinical symptoms in the early stage,then the rate of missed diagnosis or misdiagnosis is high.More and more studies have shown that Although the early left ventricular ejection fraction(LVEF)is normal,the left ventricular systolic function of HCM patients had been damaged due to the change of myocardial structure.Therefore,early detection of myocardial dysfunction in HCM patients is significant for clinical treatment and prevention of cardiovascular adverse events.Non-invasive myocardial work index(NMWI)is a new technology based on the two-dimensional speckle tracking technology of echocardiography.It is considered the influence of cardiac afterload,combining the global longitudinal strain(GLS)of the left ventricle with the left ventricular pressure,which provides a new tool for 他the evaluation of left ventricular systolic function.Objective The NMWI was used to quantitatively study the left ventricular global and regional myocardial work in patients with nonobstructive hypertrophic cardiomyopathy(NHCM),and to explore the clinical value of the technique in evaluating the systolic function of left ventricle in NHCM patients.Methods Forty-two NHCM patients(Case group)and 22 healthy subjects(Control group)matched gender and age were selected in people’s Hospital of Zhengzhou University from March 2019 to October 2020.GEVivid E95 color Doppler ultrasound diagnostic instrument with M5Sc-D probe(frequency 1.5~4.6 MHz)were used to measure conventional echocardiography parameters,two-dimensional dynamic images of three-chamber,four-chamber and two-chamber tangential planes of left ventricular apex were collected.The forward blood flow spectrum of mitral valve and aortic valve were collected by color Doppler mode.The NMWI was used to evaluate the left ventricular global and segmental myocardial work.The average values of myocardial regional work index(RWI)and regional work efficiency(RWE)at different levels(basal segment,middle segment and apical segment)were calculated,the differences of conventional ultrasound datas,GLS,global and segmental myocardial work parameters of left ventricle between the two groups were compared.The global myocardial work parameters including global work index(GWI),global constructive work(GCW),global wasted work(GWW)and global work efficiency(GWE).Pearson correlation analysis was used to analyze the correlation between continuous variables,and Bland-Altman drawing method and intra-group correlation coefficient(ICC)were used to test the repeatability of measurement results within and between observers.Results1.Conventional echocardiographic parameters: Compared with the control group,IVST、LVPWT、IVST/LVPWT、MWT、LVMI、RWT and LAD in the case group were increased,while E/A was decreased and there was significant difference(all P<0.05).There was no significant difference in LVSd,LVDd,LVESV,LVEDV and LVEF(P > 0.05).2.The global myocardic work parameters of left ventricle: Compared with the control group,the absolute value of GLS,GWI,GCW and GWE in the case group decreased significantly,while GWW increased,and the difference was statistically significant(all P < 0.05).3.The regional myocardial work parameters of left ventricle: Compared with the control group,RWI and RWE at all levels(basal segment,middle segment and apex segment)in the case group were decreased and there was significant difference(P<0.05).In the control group,RMW showed gradient characteristic at all levels.which was increased from basal segment to apical segment and there was significant difference(all P<0.05).In the case group,there was no gradient characteristics at all levels,there was no significant difference in RWI between basal segment and middle segment,but there was increased in apical segment(P < 0.05).RWE of middle and apical segments were increased compared with basal segment(P < 0.05),but there was no significant difference between middle and apical segments(P > 0.05).4.Pearson correlation analysis: GWI,GCW and GWE were positively correlated with the absolute value of GLS(r = 0.937,0.909,0.741,P=0.000)and LVEF(r =0.614,0.572,0.486,P=0.000).while GWW was negatively correlated with the absolute value of GLS and LVEF(r =-0.551,-0.534,P=0.000).GWI,GCW and GWE were significantly correlated with MWT,RWT and LVMI.Conclusion1.The global and regional myocardial function of left ventricle had been damaged in NHCM patients with normal LVEF.NMWI can detect the changes of myocardial work more sensitively than traditional echocardiography.2.The global myocardial work parameters were significantly related to LVEF GLS(all P=0.000).Suggesting that the global myocardial work parameters can be used to reflect left ventricular systolic function and provide a new reference index for clinical diagnosis.