Evaluation Of Left Ventricular Diastolic And Systolic Function Using Velocity Vector Imaging

BackgroundHeart failure is a heterogeneous syndrome resulting from abnormalities of cardiac structure or function.Systolic heart failure(SHF) often occurs as a result of impaired myocardial contractility which is responsible for the inability of the heart to pump blood at an output sufficient to meet the requirements of metabolizing tissues and organs,and the syndrome referred to congestion of pulmonary or systemic circulation is commonly characterized by shortness of breath,impaired exercise tolerance and edema.While diastolic heart failure(DHF) presents as increased ventricular pressure,congestion of pulmonary and impaired myocardial relaxation, which is associated with a relatively normal left ventricular ejection fraction.DHF is usually found in patients with coronary heart disease,hypertension and hypertrophic myocardiopathy.Nowadays,heart failure is becoming the main cause of the death of cardiovascular diseases.Early detection and evaluation of the left ventricular function may help reduce both incidence and prevalence of heart failure.Currently,the contractile state of left ventricular is often characterized by the ejection fraction,which is easy to obtain to roughly evaluate the function of left ventricle.But clinically,the figure type,tissue ultrasonic penetration and mitral regurgitation may lead to error assessment of systolic function by the EF.Nowadays,clinician has paid more and more attention to diastolic heart failure because of not only the fast growing incidence,but also the equal risk to systolic heart failure.Cardiac catheter examination has been considered as gold standard for left ventricular dysfunction with the limitation of trauma and low repeatability for clinical application.In addition,Blood Doppler(E/A) cannot reflect LV diastolic function on various occasions.Therefore,how to evaluate LV diastolic function by non-invasive method has become a hot spot.Tissue Doppler imaging has made rapid development of non-invasive measure of velocity of myocardium movement.It is showed by many basic and clinic studies that measurement of LV basal('annular'),longitudinal myocardial shortening or lengthening velocity is a good method to evaluate LV diastolic and systolic function. In 2007,the ratio of early mitral valve flow velocity(E) to mean of early peak diastolic velocity(Em) has become the basis of diagnosis DHF by the European study group on diastolic heart failure.It is also discovered that TDI has angle-dependence on measuring velocity of myocardium movement which affect its accuracy.As a new technology,Velocity vector imaging(VVI) originates from two dimension speckle tracing imaging without angle-dependence,and can accurately measure the velocity of myocardium movement.The aim of this study is to find a good non-invasive method to accurately evaluate LV diastolic and systolic function by VVI.ObjectiveThe aim is to validate the efficacy of VVI for evaluating left ventricular diastolic and systolic function by comparing with LVEDP or +dp/dt max.In the same time,we have multiple comparised different method or mearing index to find a better way to evaluate left ventricular function.Method Animal studyEight healthy mongrel dogs were studied.After opening chest,a home-made artery constrictor was placed around the proximal coronary to make different grades of coronary artery stenosis.Mean of peak diastolic velocity(Em),mean of peak systolic velocity(Sm) was measured by VVI or QTVI;mean of peak strain rate of diastole(Esr) and mean of peak strain rate of systole(Ssr) were measured using VVI;ejection fraction(EF) was measured,at the same time,left ventricular pressure were monitor to measure LVEDP and(+dp/dt)max.Clinic studyIn clinical study,51 patients who were going to receive diagnosis or treatment by left cardiac catheter become the research objects.Mean of peak diastolic velocity(Em) was measured and calculated by VVI or QTVI,EF and ratio of early to late mitral valve flow velocity(E/A) were measured and calculated the value of E/Em In every case,we monitored and recorded the curve of LV pressure to measure LVEDP,then calculated the correction between every index to LVEDP.Statistical analysisAll data were analyzed by SPSS 16.0 software.Statistically significant different was defined as the level of 0.05(bilateral).Mean comparison in groups was conducted with single factor variance analysis and the pairwise comparison was performed with LSD method when equal variances were assumed,Mean comparison in groups was conducted with Welch analysis and the pairwise comparison was performed with Tambane's T2 method when equal variances were not assumed. Correlation of two measurement indexes was analyzed using the Pearson correlations analysis,and comparison of two correlation coefficients was used Z-test.ResultAnimal study In animal study,There was a good linear correlation between Em or Esr by VVI or Em by QTVI and left ventricular end diastolic pressure(LVEDP)(r=-0.834, P＜0.001 and r=-0.703,P＜0.001 respectively).Em by VVI and LVEDP had a better correlation than that between Esr by VVI or Em by QTVI and LVEDP(Z=2.125, P=0.032 and Z=2.625,P=0.0087).Sm and Ssr by VVI,Sm by QTVI,EF had a significant correlation with +dp/dt max(r=0.883,P＜0.001,r=0.772,P＜0.001,r =0.715,P＜0.001 and r=0.647,P＜0.001,respectively).A significant difference was observed for correlation coefficient between Sm by VVI and Ssr by QTVI,Sm by QTVI,EF(P＜0.001).Clinic studyIn clinic study,there was significant correlation between E/Era by VVI or QTVI and LVEDP(r=0.808,P＜0.001 and r=0.692,P＜0.001 ) and the former was higher (Z=2.13,P=0.033),Em by VVI and QTVI had a good liner correction with LVEDP (r=-0.740,P＜0.001 and r=-0.567,P＜0.001),the former was higher than the latter (Z=2.595,P=0.009),and E/A had little correction with LVEDP。ConclusionIn this study,we has first applicated velocity vector imaging(VVI) which was the latest technology of basing on the principle of two-dimensional speckle tracking into the evaluation of left ventricular diastolic and systolic function.In animal studies, Em and Sm of the LV of dogs were measured by VVI to evaluate left ventricular diastolic and systolic function in the varying degrees of acute myocardial ischemia condition;In clinical study,Em were measured of 51 cases whose left ventricular systolic function were preserved(EF≥40%) by VVI and the ratio of early diastolic mitral flow velocity(E) to Em(E/Era) were calculated for evaluation of diastolic function.At the same time,left ventricular pressure curve was recorded to measure LVEDP. In the domestic and foreign we have firstly proved that Em and E/Em by VVI are closely related to LVEDP by cardiac catheterization which is considered as the gold standard of evaluation of left ventricular diastolic function.Em and E/Em by VVI can instead of LVEDP for evaluation of left ventricular diastolic function as a non-invasive method in clinic and is more accuracy than QTVI for measuring Em.We have also made the first application of VVI for measuring Sm of left ventricular to evaluate systolic function,and Sm by VVI has a good linear correlation with +dp/dt max by cardiac catheterization and it shows that Sm by VVI is a more sensitive and accuracy echocardiography index to evaluate left ventricular systolic function than that by QTVI or EF.It is more suitable for clinical measurement of LV systolic function.