Dynamic Study Of Cardiac Diastolic Function In Spontaneously Hypertensive Rat Model And Efficacy Of ACE Inhibitors In Chronic Heart Failure With Preserved Ejection Fraction

Heart failure is the end stage of a variety of acute and chronic cardiovascular diseases, and the incidence of heart failure is rising globally. Diastolic dysfunction and diastolic heart failure (DHF) are a group of clinical syndromes manifested by impaired diastolic function and relatively normal or preserved systolic function (LVEF>40%～50%). Epidemiological data revealed that the prevalence of DHF weighed about50%of chronic heart failure, and that the annual mortality of DHF was22%-29%, which was almost the same as that of systolic heart failure (SHF). However, till now, there are just a few studies on diastolic dysfunction and diastolic heart failure, hitherto, the treatment of DHF is still a controversy. This mainly is due to the lack of a good model and comprehensive assessment method.DHF is often occurred in elderly female, with hypertension and diabetes mellitus as major comorbidity. Of which, hypertension is the major cause of DHF because of its high prevalence. Spontaneously hypertensive rat model was often used to study the mechanism of hypertension; little is known about the progression and the mechanism of DHF from hypertension in this model, because there is a limit to assess cardiac function by echocardiography in that the rats have a small heart, thin chest wall and high heart rate. Homodynamic analysis, isotope methods and magnetic resonance imaging (MRI) are expensive, complicated and have poor reproducibility, these methods seem unqualified to assess cardiac structure and function feasibly.High resolution echocardiography (frequency range:12.5MHz-60MHz) could obtain clear images, making it possible to noinvasively measure cardiac structure and function reproducibly. However, the methodology of this technology is still not standardized.The aim of this study is to acquire a variety of parameters for cardiac structure and function by transthoracic high frequency echocardiography, and to observe histological and serological indices following the transition of cardiac function, to better use this model for the study of diastolic function and diastolic heart failure.Adiponectin was found to be cardioprotective in recent years, we aim to observe the change of adiponectin with deterioration of cardiac function through histological and serological studies and specify the source of adiponectin, to make it possible for early intervention.Angiotensin-converting enzyme inhibitors (ACEI) could lower blood pressure and lessen myocardial hypertrophy; it has been proved that ACEI is efficient in the treatment of systolic heart failure; however, the prognostic effect of ACEI in DHF is still inconsistent. We carried out a meta analysis to identify the effect of ACEI in diastolic heart failure patients.Part One Time Series Evaluation of Cardiac Function in Spontaneously Hypertensive Rats by High Frequency EchocardiographyAims:To perform a noninvasive evaluation of the time course of changes in cardiac structure and function of spontaneously hypertensive rats (SHR) in vivo by echocardiography to learn more about the cardiac effects of hypertension.Methods:Thirty five male SHR were used, after systolic blood pressure, body weight and heart rate data obtained, echocardiography were determined at1,3,6,9,12,15and18months of age, respectively, each age group have5rats. Being anesthetized, transthoracic echocardiographic measurements were performed in the supine position with a high frequency echocardiographic probe RMV-716using a17.5MHz transducer. The probe was placed to obtain parasternal long-axis cardiac views. From this view, an M-mode trace of the LV was obtained, and LV end-diastolic diameter (LVEDD), LV end-systolic diameter (LVESD), LV posterior wall thickness (LVPW) and interventricular septum thickness in diastole (IVS) were measured. LV ejection fraction (EF) and fractional shortening (FS) were measured directly from the long-axis image. Using pulsed-wave Doppler imaging, we measured maximal velocities of the E and A waves of mitral inflow, E/A ratio was calculated. Using tissue Doppler imaging, we also recorded wall movement at the level of the lateral mitral annulus from the parasternal long-axis view, and also measured maximal velocity of early (E’) and late (A’) diastolic waves. E’/A’ was calculated. After echocardiography, LV was harvested and cut into cross sections about5mm thick and then fixed with10%neutral-buffered formalin solution, stained with hematoxylin and eosin (H&E) for routine histological examination to observe myocardial hypertrophy, and with Masson stain to evaluate the degree of fibrosis.Results:We found body weight of SHR increased insistently with age and kept steady after6months of age; systolic blood pressure (SBP) of SHR elevated at3months postpartum, to171±3.1mmHg, and persistently high till18months of age at200mmHg. Echocardiography demonstrated concentric hypertrophy from3months of age as shown by the increase of LVPW, IVS and LVEDD compared to those of1month of age. With the elevation of systolic blood pressure, cardiac diastolic function measured by pulsed-wave Doppler and tissue Doppler imaging showed that E/A ratio significantly decreased and E’/A’ value was less than one from6months of age and lasted to18months of age. Systolic function assessed by ejection fraction (EF) and fractional shortening (FS) declined at18months of age, the change was statistically significant. Histopathological examinations showed evident myocardial hypertrophy and interstitial and perivascular fibrosis with aging.Conclusions:High frequency transthoracic echocardiography approach has a great feasibility to obtain high quality of cardiac images and measure many parameters of both cardiac structure and function in SHR. SHR exhibited evident hypertrophy (3months of age) and cardiac diastolic dysfunction during a long time frame (from6months to18months of age) and eventually transited into overt diastolic heart failure; accordingly, the heart mainly manifested myocardial hypertrophy and interstitial and perivascular fibrosis. They could be a good model for the study of diastolic dysfunction and consequent diastolic heart failure. Part Two Histological and Serological Changes of Adiponectin with the Change of Cardiac FunctionAims:To explore the histological and serological changes of adiponectin with the development of cardiac function and specify the source of adiponectin.Methods:After echocardiography completed, the rats were sacrificed and1ml blood was sampled from the inferior vena cava, then centrifugated by15000rad/m for20min, at4℃for measurement of serum IL-6, NT-proBNP and adiponectin levels. Pericardial, perinephric and mesenteric adipose tissue were harvested to find out the main source of adiponectin using RT-PCR, and to observe the change of adiponectin following the transition of cardiac function.Results:Our results clearly demonstrated that serum IL-6(pg/ml) was sharply increased from13.24±1.26(1month) to621.45±19.49(18months), meanwhile, serum NT-proBNP (fmol/ml) also elevated from172.79±4.32(1month) to541.31±7.09(18months). In the mean time, however, adiponectin (ng/ml) was initially decreased during first6months as evidenced by diastolic dysfunction from15.20±1.22(1month) to10.60±2.32(6months) and then reached plateau for the rest period study between9.31±1.84ng/ml～11.65±1.35ng/ml. And adiponectin level was inversely correlated with serum IL-6and NT-proBNP levels (correlation coefficient was-0.568for IL-6, p=0.007and-0.606for NT-proBNP, p=0.005, respectively). Interestingly, RT-PCR demonstrated that expression of adiponectin by adipose tissue increased at6months of age rats, the mechanism of which was unclear, and we also found there is no tissue difference for expression of adiponectin among visceral adipose tissues.Conclusions:We demonstrated that serum adiponectin level decreased as diastolic dysfunction occurred and inversely correlated with serum IL-6and NT-proBNP levels, however, mRNA expression of adiponectin elevated with the development of cardiac function, thus adiponectin may be a useful biomarker during transition from hypertension to left ventricular diastolic dysfunction and onset of diastolic heart failure. There is no tissue difference for expression of adiponectin among visceral adipose tissues. Part Three Efficacy of ACE inhibitors in Chronic Heart Failure with Preserved Ejection Fraction:Meta Analysis of7Prospective Clinical StudiesBackground:The effect of ACE inhibitors on the prognosis of chronic heart failure patients with preserved left ventricular ejection fraction remains controversial.Aims:To assess the impact of ACE inhibitors on the prognosis of chronic heart failure patients with preserved left ventricular ejection fraction.Methods:We used Pubmed, EMBASE, BIOSIS, the Cochrane Library (Issue3,2009) and OVID databases to search for all electronically registered clinical trials by means of the following keywords:angiotensin-converting enzyme inhibitor, captopril, enalapril, benazepril, perindopril, alacepril, zofenopril, cilazapril, quinapril, ramipril, spirapril, imidapril, delapril, lisinopril, fosinopril, trandolapril, heart failure with preserved ejection fraction, heart failure with normal left ventricular ejection fraction, diastolic heart failure, heart failure with normal systolic function, human and all languages were included. Additionally, a manual search of previous meta-analyses and reviews on ACE inhibitors was performed and all relevant reference lists were screened. Inclusion criteria were:(1) prospective study design (i.e. patients identified and data collected at the start of follow-up);(2) assessment of the effectiveness of ACE inhibitors versus placebo, or other classes of drugs, as monotherapy or first-line therapy for heart failure with preserved ejection fraction (defined as signs or symptoms of heart failure and EF>40%);(3) outcome data available (mortality, readmission,6-min walk distance and quality of life);(4) at least a six month follow up in either study arm. Two authors independently abstracted the data and assessed the eligibility and methodological quality of each trial. Information about patient characteristics (age, gender, left ventricular ejection fraction and etiology of HFPEF), intervention strategies and measures of endpoints (i.e. mortality, readmission,6-min walk distance and quality of life) was systematically extracted. The available data on6-min walk distance and quality of life (QOL) were found to be insufficient for a meta-analysis. Extracted data were analyzed by determining the odds ratio (OR) pertaining to the ACE inhibitor treated group versus controls. All analyses were performed using The Cochrane Collaboration Review Manager software and STATA-10, with a significance level set at0.05.Results:Seven prospective studies evaluating the effect of ACE inhibitors compared to placebo or other drug classes, as monotherapy or first-line therapy, on the prognosis of chronic heart failure patients with preserved left ventricular ejection fraction were included. A total of2554patients (mean age:75.1years, female:58%) were recruited with an average follow up of20.9months. The primary etiology of heart failure with preserved ejection fraction was ischemic heart disease (33.7%), hypertension (69.1%) and diabetes mellitus (25.8%). Combined results demonstrated that ACE inhibitors significantly reduced all-cause mortality (Odds ratio (OR)=0.52;95%Confidence Interval (CI),0.41to0.64; P<0.00001). Furthermore, ACE inhibitors were able to reduce heart failure related rehospitalization in a subgroup of patients aged over75years or treatment over20.9months (p<0.05). However, death due to worsening of heart failure, heart failure related rehospitalization and any-cause readmission were not improved compared to control group (OR=0.88;95%CI:0.66to1.17; P=0.37for death due to worsening of heart failure; OR=0.81;95%CI:0.63to1.05; P=0.11for heart failure related rehospitalization and OR=0.88;95%CI:0.68to1.14; P=0.33for any-cause readmission, respectively).Conclusions:In patients with chronic heart failure with preserved ejection fraction, ACE inhibitors reduced all-cause mortality without affecting mortality due to heart failure and any-cause rehospitalization.