Clinical Study On The Structural And Functional Changes Of Arteries In Essential Hypertension Patients With Left Ventricular Hypertrophy

Background:Essential hypertension(EH)is one of the most common cardiovascular diseases. With the extension course of hypertension,myocardial morphous develops myocardial remodling such as left ventricular hypertrophy(LVH)in reason of persistent increase of afterload and persistent reinforcement of ventricular tension at diastole,so left ventricular hypertrophy is one of severe complications in hypertensive epatients.Left ventricular hypertrophy is not only the common target organ damage, but also the sign of ventricular remodling in the process of heart failure.Left ventricular hypertrophy which is an important predictor of many cardiovascular envents has close correlation with the degression of heart relaxation and contraction function,the decrease of coronary arterial reserve,the occurrence of arrhythmia and the activity of cardiac autonomic nerve.The large scale epidemiological investi gations such as Frahaming study have manifested that LVH is an independent risk factor of prognosis in cardiovascular diseases.The case fatality rate of hypertensive patients with LVH is eight times than that of hypertensive patients without LVH. Thus,the important therapeutic target of hypertension is the prevention and retro conversion of LVH.Long term arterial hypertension can results in the structural and functional changes of peripheral arteries.In fact,many hypertensive patients have developed a series of changes in peripheral arteries before the appearance of LVH, which manifestes endothelial dysfunction,increase of arterial stiffness and appearance of atheroscleosis in large arteries.Therefore,it is very important to investigate the relationship between arteries remodling and LVH for deferring the development of LVH and improving the hypertensive patients prognosis.In June 2004,the ministry of Public Health has authorized the techniqes for early vascular disease detection and has spreaded it to entire country as one of hundred programs in decade.And the comprehensive appliance of detection techniques in《Chinese Guideline for Early Vascular Disease Detection》can identify vascular disease earlier,defer the development of LVH and prevent acute cadiovascular events.In this study,we detect many parameters reflecting the structural and functional changes in the early vascular disease detection system,and can omnibearingly and systemic identify earlier peripheral vascular disease.In recengt years,the researches based on the structural and functional changes of peripheral arteries in hypertensive patients are more and more.How do peripheral arteries develop some changes before and after the appearance of LVH in hypertensive patients? What are the influential factors of LVH in hypertensive patients? How does peripheral arterial remodling play pole in the in the occurrence and development of LVH? And how to identify subclinical vascular lesion in the early stage? The above problems constitute the objective and contrivable idea of this topic. The cut-in point of this topic bases on arterial remodling in hypertensive patients,and intensively explore the functionary mechanism of peripheral arterial remodling in the occurrence and development of LVH.Objective:(1)To investigate the structural and functional changes of peripheral arteries in hypertensive patients with left ventricular hypertrophy,and indentfy the relationship between peripheral arterial remodling and left ventricular hypertrophy.(2)To apply the detection techniques in《Chinese Guideline for Early Vascular Disease Detection》to overall identify earlier structural and functional changes of peripheral arteries,and provid theoretical evidence for generalization of the detection techniques.Methods:1.Study populationsFrom November 2006 to May 2007,one hundred and forty consecutive subjects in Qilu Hospital of Shandong University were enrolled in this study.They included one hundred hypertensive patients and forty normal subjects.Hypertensive group includes 47 men,53 women,age rang 27～71 years,mean age 51.51±9.37 years. According to《Chinese Guideline for prevention and treatment of hypertension in 2005》,Hypertensive patients were defined as having arterial hypertension if they had blood pressure readings above 140/90 mmHg in the hypertension clinic or in the process of anti-hypertensive therapy.The subjects with medical history of secondary hypertension,hyperlipemia,diabetes,hypertrophic cardiomyopathy and cardiac insufficiency were excluded in this study.LVMI＞120 g/m² in men and＞115 g/m² in women was considered as left ventricular hypertrophy.We divided the hypertensive patients into two groups on the basis of LVMI as follows:â‘ the group of LVH:24 women,26 men,age rang 27～67 years,mean age 50.51±9.42 years;â‘¡the group of NLVH:23 women,27 men,age rang 32～71 years,mean age 52.51±9.33 years.The normal subjects included 20 women,20 men,age rang 29～73,mean age 47.88±9.57 years.They had no medical history,normal physical examination and auxiliary examination.2.InstrumentationGE Vivid7 ultrasound machine had a M3S transducer(2.5 to 4.0MHz)and a high resolution linear-array transducer(5 to 10MHz).The Vivid7 equipped with two-dimen sion echocardiograms,M-mode echocardiograms,pulsed-wave Doppler,continous-wave Doppler and color Doppler flow imaging.An standardâ…¡lead ECG monitor inte grated with the ultrasound machine was applied.The arteriosclerotic examine device (VP-1000,Colin,Japan)was also applied.3.Examination3.1 Echocardiographic Image AcquisitionIn the parasternal long axis view of left ventricle,two-dimensional guided M-mode echocardiograms measured three cycles of septal(IVSd)and posterior wall thickness(PWTd)as well as left ventricular internal diastolic(LVDd)at the level of chordae tendineae.The following formula was used for the estimation of left ventricularmass: LVM(g)=0.80×[1.04×(IVSd+LVDd+PWTd)³-(LVDd)³]+0.6;LV mass index(g/m²)=LVM/BSA;BSA=(0.0061×height+0.0218×welght)—0.1529.3.2 Carotid ultrasonographyThe carotid artery examination was performed with a high-resolution ultrasound device equipped with a 7.5MHz linear-array transducer.The parameters included ima ges of the common(CCA),the bifurcation(BIF),the internal(ICA)and external carotid artery(ECA),the diameter of common carotid artery(CCA-D)and intima-media thickness (IMT),the plaques in the both carotid arteries,arterial compliance(AC),alasticity coefficient(Ep),stiffness coefficient(β),peak systolic velocity(PSV),peak diastolic velocity(EDV),mean velocity(MV),resistent index(RI)and pulsatelity index(PI).3.3 Measurements of FMD in the brachial arteryAccording to Celermajer's method,we measured the internal dameter(D₀),mean velocity(V₀),blood flow volume(Q₀)of brachial artery at rest,and the internal dameter (D₁),mean velocity(V₁),blood flow volume(Q₁)of brachial artery after reactive hyperemia.The change rate of the internal dameter(â–³D%)=(D₁—D₀)/D₀×100%.The brachial blood flow(Q ml/min)=60×V×pD²/4.The change rate of flow volume(â–³Q%) =[(Q₁—Q₀)]/Q₀×100%.3.4 The measurements of brachial-ankle pulse wave velocity(baPWV)and ankle-brach ial index(ABI)were performed using a arteriosclerotic examine device.4.Statistical analysisAll statistical analysis were performed using SPSS version11.5.The numerical data presented as mean±S.D,and the categorical data were described by example and percentage. Comparisons of among three groups used the ANOVA-test,and comparisons between two groups were performed with the student q-test if necessary.Categorical difference was analyzed by Chi-squared test.Bivariable simple correlationanalysis was performed with Pearson analysis,and multiplicity were used by multiple stepwise regression analysis.All tests were two-sided and a value of P＜0.05 was considered statistically significant.Results1.1 The comparison of common characteristics The common characteristics between the three groups subjects have no statistical significance(P＞0.05)except for blood pressure,BMI and LVMI.So there is comparability among the three groups.1.2 The comparison of carotid arterial structure and elasticityThe internal diameter,IMT and plaques of CCA increased significantly in hyper tensive patients than that of normal subjects(P＜0.05).Ep andβwere higher in hyper tensive patients than that of the normal subjects,and AC was lower in hypertensive patients(P＜0.05).All indices were changed most significantly in LVH patients.1.3 The comparison of carotid arterial hemodynamic parametersCompared with the normal subjects,the hemodynamic parameters strikingly decr eased and the resistant parameters significantly increased in hypertensive patients(P＜0.05).And these parameters such as CCA-PI,CCA-RI,ICA-PI,ICA-RI had statis tical significance between NLVH and LVH groups(P＜0.05).1.4 The comparison of endothelial functionCompared with the normal subjects,the internal dameter and blood flow volume slightly increased at rest and after reactive hyperemia,but had no statistical significan ce(P＞0.05).However,the change rate of the internal dameter(â–³D%)and blood flow volume(â–³Q%)in brachial artery decreased obviouslly in hypertensive patients(P＜0.05),especially in LVH patients..1.5 The comparison of arterial stiffness and occlusionBaPWV was highest in LVH subjects,and the second was NLVH patients(P＜0.01).ABI among the three groups were in the normal range and had no statistical significance(P＞0.05).1.6 The Pearson analysis of LVMIThe Pearson analysis showed that LVMI was positively correlated with SBP,DBP,PP,BMI,IMT,RI,baPWV(the value of simple correlation coefficient was respectively 0.517,0.273,0.420,0.386,0.221,0.374,0.575,P＜0.01),and LVMI was negatively correlated with AC,EDV,PSV,PI,FMD in hypertensive patients(the value of simple correlation coefficient was respectively -0.237,-0.323,-0.257,-0.314, -0.205,P＜0.05). 1.7 Multiple stepwise regression analysis of LVMIMultiple stepwise regression analysis using LVMI(Y)as a dependent variable was conducted to determine the relative contributions made by each variable to the outcome variable.SBP,DBP,PP,BMI,IMT,AC,EDV,PSV,PI,RI,FMD,baPWV were employed as independent variables.The result showed that baPWV(X1),SBP(X2),PP(X3)and BMI(X4)were employed into the regression equation,Y=5.943+0.545X1+0.457X2+0.372X3+0.321X4.Conclusions1.Hypertensive patients have developed the structural and functional changes of peripheral arteries before the appearance of LVH.Arterial remodling manifested endothelial dysfunction,impairmen of arterial compliance,increase of IMT and appearance of atheromatous plaques in carotid arteries.Furthermore,hemodynamic parameters of carotid arteries revealed low velocity and high resistence.The structural and functional changes of peripheral arteries aggravated progressively in LVH patients,and all above parameters were changed most significantly in LVH patients.2.The LVMI was positively correlated with SBP,DBP,PP,BMI,IMT,RI,baPWV, and LVMI was negatively correlated with AC,EDV,PSV,PI,FMD in hypertensive patients.Multiple stepwise regression analysis showed that the independent risk factor of LVMI was respectively baPWV,SBP,PP,BMI,especially baPWV.3.Arterial remodling developed before the appearance of LVH,and arterial remodling may paly an important role in the occurrence and development of LVH.The increase of arterial stiffness is an important reason in the occurrence of LVH.4.The detection techniques in《Chinese Guideline for Early Vascular Disease Detecti on》can reliably overall identify earlier structural and functional changes of peripheral arteries.The discrimination of subclinical vascular lesion in the early stage was very important for preventing the future occurrence of acute cardiovascular and cerebral events.Therefore,this study provided theoretical evidence for generalization of the detection techniques.