| Part Ⅰ Evaluation of myocardial systolic function in spontaneously hypertensive rats by echocardiographic layer-specific myocardial strainObjective:Two-dimensional speckle tracking echocardiography(2D-STE)was used to measure layer-specific myocardial strain to evaluate the changes of left ventricular(LV)systolic function in spontaneously hypertensive rats(SHR)and normal blood pressure rats(Wistar-kyoto rats,WKY).And to explore the pathological and molecular biological reasons for the changes of myocardial systolic function in SHR rats.Methods:We chosen 24 SHR and 24 WKY for this research.All rats were anesthetized by intraperitoneal injection of 35 mg/kg 3%(w/v)sodium pentobarbital.Echocardiography was performed after the rats entered deep anesthesia.Parasternal short-axis view at papillary muscles level and apical four chamber view were recorded and for the off-line analysis.Layer-specific global longitudinal strain(GLS),contained epimyocardial,middle layer and endomyocardial(GLSEpi,GLSMid and GLSEndo)in the apical four chamber view,layer-specific global circumferential strain(GCS),contained epimyocardial,middle layer and endomyocardial(GCSEpi,GCSMid and GCSEndo),global radial strain(GRS)in shortaxis view at papillary muscles level were measured by 2D-STE.SHR and WKY were executed(death mode:cervical dislocation),exposed the chest and collected the heart.After the heart was isolated,the right atrial appendage was cut off,and a sufficient amount of 4℃ precooled PBS was slowly injected from the aorta with a disposable 5 ml syringe until colorless and transparent liquid flowed out.Fixed the heart with a pin,observed the size and shape of the heart,collected the myocardial tissue of the left atrium(LA)and LV,compared the thickness of the LV myocardium,and put it into 4℃ precooled paraformaldehyde for tissue fixation and-80℃ freezing for standby.Hematoxylin-eosin staining(HE staining)for diagnosis of hypertrophy and hyperplasia of cardiomyocytes and Masson staining for diagnosis of myocardial fibrosis.The expression of mRNA of transforming growth factor beta l(TGFβ1)and SERCA2a were detected by qPCR.The expression of protein levels of TGF-β1 and SERCA2a were detected by Western blot.Results:There were significant differences in GLS,GCS and GRS between SHR and WKY(P<0.001),the absolute values of these varibles in SHR were significantly lower than WKY.HE staining showed myocardial hypertrophy and hyperplasia and Masson staining showed myocardial fibrosis in SHR.The expression of mRNA of TGF-β1 was significantly increased while SERCA2a was significantly declined in SHR(P<0.001).The expression of protein level of TGF-β1 was significantly increased while SERCA2a was significantly declined in SHR(P<0.001).Conclusion:The LV systolic function was impaired in SHR and this can be detected by layerspecific global myocardial strain by 2D-STE.The impaired LV systolic function maybe related to myocardial proliferation,hypertrophy,myocardial fibrosis.And also related the increased expression of mRNA,protein level of TGF-β1 and declined expression of SERCA2a.Part II Myocardial strain,strain rate and volume-derived values for detection the subclinical left atrial myocardial dysfunction in essential hypertension patients with normal left ventricle ejection fractionObjective:During the cardiac cycle,the left atrial(LA)as a reservoir,conduit and booster pump plays an important role in the contraction and relaxation of the heart.The research was to investigate subclinical LA myocardial dysfunction in essential hypertension(EHT)patients with normal left ventricular ejection fraction(LVEF)by using myocardial strain,strain rate and volume-derived values.Methods:A total of 100 EHT patients with normal LVEF and 55 normal controls were enrolled in this study.EHT patients were divided into two groups according to left ventricular myocardial mass index(LVMI):EHT without left ventricular hypertrophy(LVH)and EHT with LVH.Echocardiography was performed and the apical 4-and 2-chamber views(all contained LA)of three consecutive cycles were stored for off-line analysis.The maximum LA volume(LAVmax),the precontraction LA volume(LAVpre)and the minimum LA volume(LAVmin)were measured in the 2D echocardiography images in the apical 4-and 2-chamber views.Then,total LA stroke volume(LASV),passive LASV,active LASV,total LA ejection fraction(LAEF),passive LAEF and active LAEF were calculated.LA strain(S-reservoir,Sconduit,and S-booster pump)and strain rate(Sr-reservoir,Sr-conduit,and Sr-booster pump),containing reservoir,conduit and booster pump functions,were measured by two-dimensional speckle tracking echocardiography(2D-STE).Total LAEF,S-reservoir,and Sr-reservoir represented the reservoir function,Passive LAEF,S-conduit,and Sr-conduit represented the conduit function,and Active LAEF,S-booster pump and Sr-booster pump represented the booster pump function,respectively,and then to compare the differences of these values between the EHT patients and normal controls,and also to compare the differences of these values among the EHT patients without LVH,EHT patients with LVH and normal controls.Results:There were significant differences in Total LAEF,Passive LAEF,Active LAEF,S-reservoir,S-conduit,Sr-reservoir,Sr-conduit,Sr-booster pump between EHT patients and normal controls(P<0.05),the absolute values in EHT patients were significantly lower than those in normal controls.The absolute values of Total LAEF,Passive LAEF,S-reservoir,S-conduct,Sr-conduct and Sr-booster pump in EHT patients with LVH were significantly lower than those without LVH and those in normal controls(P<0.05).However,there were no significant differences in Active LAEF,S-booster pump and Srbooster pump functions between EHT patients without LVH and normal controls(P>0.05).Receiver operating characteristic(ROC)analysis showed the areas under the curves(AUC)of the combination of volume-derived values,LA strain and strain rate were significantly higher than individual indices(P<0.05).Conclusion:From the research,EHT patients(regardless the LV is hypertrophy or not)showed a decreased LA functions(reservoir,conduit and booster pump)compared with those of normal controls.The impairment of LA functions(reservoir,conduit and booster pump)is more serious in EHT patients with LVH than without LVH and normal controls.In EHT patients without LVH,the LA booster pump function is normal,while the function is impaired in EHT patients with LVH.Myocardial strain and strain rate combined with volume-derived values could provide a sensitive and reproducible method for detecting subclinical LA myocardial dysfunction.Part Ⅲ Global myocardial work for detection the subclinical left ventricle myocardial dysfunction in essential hypertension patients with normal left ventricle ejection fractionObjective:It is still challenging for evaluating the subclinical left ventricular(LV)myocardial dysfunction in patients with essential hypertension(EHT)by echocardiography noninvasively.The aim of this study was to determine whether global myocardial work(MW),derived from non-invasive LV pressure-strain loops(PSL)at rest,could predict subclinical LV myocardial dysfunction in essential hypertension(EHT)patients with normal left ventricle ejection fraction(LVEF).Then compared with layer specific global longitudinal strain and to prove its advantage.Methods:A total of 105 EHT patients with normal LVEF and 55 normal controls were enrolled in this study.EHT patients were divided into two groups according to left ventricular myocardial mass index(LVMI):EHT without left ventricular hypertrophy(LVH)and EHT with LVH.Apical 4-,3-and 2chamber views were acquired by two-dimensional echocardiography.The peak systolic myocardial layerspecific longitudinal strain(Epimyocardial GLS:GLSEpi;Middle layer GLS:GLSMid;and Endomyocardial GLS:GLSEndo),global myocardial work index(GWI),global constructive work(GCW),global wasted work(GWW)and myocardial work efficiency(GWE)were measured by twodimensional speckle-tracking echocardiography(2D-STE).Then to compare the differences of these values between the EHT patients and normal controls,and also to compare the differences of these values among the EHT patients without LVH,EHT patients with LVH and normal controls.Results:The absolute values of GLSEpi,GLSMid and GLSEndo in EHT patients were significantly lower than normal controls(P<0.05).The values of GWI,GCW,GWW in EHT patients were significantly larger than normal controls,while GWE was significantly lower than normal controls(P<0.05).The absolute values of GLSEpi,GLSMid and GLSEndo were significantly lower in EHT patients with LVH than in EHT patients without LVH and normal controls(P<0.05).There were significant differences in GWI,GCW,GWW,and GWE between EHT without LVH and normal controls(P<0.05),the values of GWW GWI,GCW and GWW were significantly larger than normal controls,while GWE was significantly lower than normal controls.GWE was significantly reduced in EHT patients with LVH compared without LVH and normal controls(P<0.05).ROC analysis showed that the AUC of combined global MW values(GWI,GCW,GWW and GWE)was significantly higher than combined layer-specific GLS(GLSEpi,GLSMid and GLSEndo)for detecting the accuracy of LV subclinical dysfunction in EHT patients(P<0.05).Conclusion:From the study,we concluded that LV systolic function was subclinically impaired in EHT patients(regardless the LV is hypertrophy or not)with preserved LVEF.Global MW is a potential new technique that allows a better understanding of the relationship between LV remodelling and increased wall stress under different stages of hypertension.Global MW is a sensitive predictor of subclinical LV myocardial dysfunction from without LV remodelling to remodelling compared with myocardial layer-specific strain analysis. |
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