Utility Of Echocardiography In Diastolic Function: Comparison With Plasma Level Of Amino-terminal Pro-brain Natriuretic Peptide

BackgroundsChronic heart failure is the end stage of many different cardiovascular diseases and concerning with high prevalence and mortality.According to the changes in systolic function,it can be systolic heart failure or diastolic heart failure.Since most of the former conducted clinical trials and observational studies incorporated reduced systolic function into their diagnostic criteria for heart failure,there is few clinical data refer to isolated diastolic heart failure.Therefore,diagnosis,clinical characteristics and prognosis of diastolic heart failure remain unclear.Diastolic heart failure has emerged over the last two decades.It is generally considered diastolic dysfunction as the cause of diastolic heart failure.This clinical syndrome holds nearly half of the heart failure population with a trend in increasing prevalence through the years and it is more common in women and elder people.Its prognosis is similar to that of systolic heart failure.Treatment of this syndrome remains largely empiric because of the paucity of evidence based effective drug therapy.The diagnosis for diastolic heart failure remains unclear up to now, calling for more intensive investigation about the evaluation of diastolic function.Although invasive eatheteriazaion measurement and noninvasive echocardiographic measurements such as Doppler echocardiography and tissue Doppler echocardiography are proposed for evaluation,there are inherent restrictions concerning these methods in clinical application.How to evaluate diastolic function accurately is still pending.Brain natriuretic peptide(BNP) is a member of the natriuretic peptide family.It is synthesized and released predominantly from ventricular myocardium in response to myocyte stretch and can reflect the function of ventricle.BNP has beneficial physiological properties including down regulation of sympathetic nervous system and renal angiotensin aldosterone system,natriuresis and vasodialation. Amino-terminal pro-brain natriuretic peptide(NT-pro BNP) is the biologically inactive amino portion of pro-BNP,the precursor of BNP. Plasma levels of BNP and NT-pro BNP are both increased during ventricular dysfunction.As these natriuretic peptides increase in response to increased left ventricular filling pressure,they have been recognized as objective biological markers in diagnosing congestive heart failure by FDA as well as ESC.The established diagnostic value of these natriuretic peptides in heart failure provides an easy feasible approach for detecting diastolic dysfunction.ObjectivesUsing NT-pro BNP as a surrogate of left ventricular filling pressure, echocardiographic indexes of diastolic function including transmitral inflow velocities,pulmonary venous flow velocities,diastolic mitral annulus velocities and left atrial volume are investigated in correlation with plasma level of NT-pro BNP in patients of diastolic dysfunction to determine which index is the best reflection of diastolic function.Materials and MethodsStudy objects 38 inpatients in division of cardiology,Zhongshan Hospital were enrolled,with left ventricular ejection fraction more than 50%.All patients have concomitant cardiovascular diseases including coronary heart disease,hypertension,diabetes mellitus or non-obstructive hypertrophic cardiomyopathy.All patients were confirmed without following clinical settings:persistent atrial fibrillation,congenital heart disease,valvular heart disease,more than mild mitral regurgitation,obstructive hypertrophic cardiomyopathy, acute coronary syndrome,pacing rhythm,severe pulmonary hypertension, severe lung disease,severe renal dysfunction and liver cirrhosis with ascites.Methods Fasting blood sample was taken at 6 in the morning in all patients.Plasma concentration of NT-pro BNP was measured by sandwich principle using reagents on Elecsys 2010 analyzer provided by Roche Company Switzerland.Routine blood test,liver function,renal function and blood glucose were tested simultaneously.Echocardiography was performed within seventy-two hours after blooding sampling by a single investigator who was blind to the plasma level of NT-pro BNP with a GE VIVID 7(GE Company America) or Philips IE33(Philips Company Dutch) ultrasound machine to obtain parameters including inside dimensions of chambers,left atrial volume,left ventricular wall thickness,left ventricular ejection fraction,transmitral inflow velocities,pulmonary venous flow velocities,and diastolic mitral annulus velocities.Left atrial volume was indexed to body weight as well as to body surface area.Statistics Data were processed by SPSS 13.0 for windows.The measurement data were presented as mean±standard deviation.The correlation between plasma level of NT-pro BNP and echo indexes was analyzed by linear correlation.Statistical significance was defined as P＜0.05.ResultsThe mean age of the 38 patients(male,25,65.8%) was 62.1±13.8 years old.Coronary heart disease was found in 15 patients,old myocardial infarction in 3,hypertension in 18,diabetes mellitus in 7 and non-obstructive hypertrophic cardiomyopathy in 16.The patients' NYHA cardiac function status ranges fromⅡtoⅢ.Transmitral inflow velocities and pulmonary venous flow velocities were obtained in 24(63.2%) patients while other indexes including inside dimensions of chambers,left atrial volume,left ventricular wall thickness,left ventricular ejection fraction and diastolic mitral annulus velocities obtained in all.Left ventricular ejection fraction was more than 50% in all patients(mean,67.4±5.0%).Gender,age and BMI have no linear correlation with LogNT-pro BNP in this study.There was no correlation between LVEF,LVEDD,LVESD and LogNT-pro BNP.No correlation was found between transmittal inflow velocities,pulmonary venous flow velocities, ratio of early diastolic transmittal inflow velocity and early diastolic mitral annulus velocity and LogNT-pro BNP.There was significantly linear correlation between LAD,LAV,LAV/BW,LAV/BSA,E',A',E'/A' and LogNT-pro BNP,LAV/BW(r=0.687) and LAV/BSA(r=0.652) both have the highest coefficient correlation of all(P＜0.0001).ConclusionsTransmitral inflow velocities and pulmonary venous flow velocities can be inaccurate in evaluating diastolic dysfunction if ventricular systolic function is preserved.In this clinical setting,increased left atrial volume rather than mitral annulus velocities may predict elevated left ventricular filling pressure.