Quantitative Assessment Of Intra-Cardiac Dissipative Energy Loss Derived From Vector Flow Mapping In Patients With Atrial Septal Defect

ObjectiveAn atrial septal defect(ASD)is one of the commonly known congenital cardiac abnormalities presenting in adulthood.ASD is characterized by a defect in the inter-atrial septum,which allows pulmonary venous return from the left atrium to pass directly to the right atrium.Depending on the ASD size,the magnitude of the shunt,and associated abnormalities,this can outcome in a spectrum of disease ranging from no significant cardiac sequel to right-sided volume overload,pulmonary arterial hypertension,and even atrial arrhythmias.The blood flow through the defect that could be either from left to right or right to left is called the Shunt.The hemodynamic importance of an ASD can actually be determined by the amount of shunting.A right to left shunt usually displays the more dangerous scenario.The delicate physical examination findings and often-minimal symptoms during the first 2-3 decades of life contribute to a delay in diagnosis until adulthood,the majority(more than 70%)of which is noticed by the fifth decade of life.The most common test is a trans-thoracic echocardiogram and ASD closure has been modernized by the use of percutaneous implantation of an amplatzer septal occluder(ASO).Trans-catheter ASD closure is a standard alternative to surgery which is associated with low complication rates and short hospitalizations.Normally,blood flow during a cardiac cycle develops into a vortex within the heart chambers.This vortex kind of blood flow reduces the blood collision and maintains the energy efficiency in the normal heart by preventing needless energy dissipation.However,in case of cardiovascular disease when there is an inefficient non-physiological flow,the blood flow vorticity may change.Such as,in ASD,the vortex rotation tends to be in the opposite direction than normal that causes increased dissipation of energy.Thus,such kind of hemodynamic observations greatly help to evaluate the different heart conditions,and recently there is a great deal to estimate the intra-cardiac energy loss(EL).An immense number of approaches have been evolved over the past two decades to institute a diversity of physically meaningful constraints into myocardial motion and flow analysis.These modalities apply the spatial information from such images in order to denote computational domain.Earlier studies have elaborated that both size and function play an important role in the evaluation of systolic and diastolic dysfunction.However,the previous studies centered on volume or mechanics,but none has done much to assess the blood flow quantitatively.Hence,VFM is a novel technique in echocardiography,which uses the color Doppler imaging overlapping with speckle tracking techniques to display the velocity vectors of blood flow and estimates the flow dissipative EL.With the use of continuity equation,VFM can calculate the velocity in a direction vertical to the beam without angle dependency whereas the Doppler imaging and echo-PIV cannot perform the same function.At present,the research of EL in ASD patients is rare to see.This EL has assumed to become a new indicator of cardiac function.Therefore,it is considered an effective index to monitor the blood flow efficiency within the heart chambers under various pathological conditions.Thus,the purpose of this study was to observe the intra-cardiac energy dissipation and hemodynamic variations by applying vector flow mapping(VFM)in healthy individuals as well as in the patients with an atrial septal defect(ASD)who were treated with percutaneous occlusion.MethodsStudy populationThis cross-sectional study included 52 cases of healthy persons(mean age 48.77± 11.09 years,range 28-73,male:female ratio 18:34)and 52patients diagnosed with ASD(mean age 37.75± 16.65 years,range 9-68,male:female ratio 15:37).ExaminationWe used a UST-52105 probe(1-5 MHz)on a ProSound F75 ultrasound device while performing a trans-thoracic echocardiographic exam.Two-dimensional echocardiography used to acquire apical four chambers(Ap4)images.At least 3 cycles of dynamic images were stored for analysis.The various diameters of intra-cardiac structures such as,right atrium transverse(RAT),right atrium longitudinal(RAL),right ventricle(RV),inter ventricular septum(IVS),left ventricular posterior wall(LVPW),aorta(AO),pulmonary artery(PA),pulmonary pressure(PP),right atrial area(RAa),left atrial area(LAa),right ventricle end diastolic area(RVEDa),right ventricle end systolic area(RVESa)were determined in control and case groups according to the current recommendations.We applied the biplane Simpson's method was used to calculate the left ventricle ejection fraction(LVEF),right atrium(RA)and left atrium(LA)volumes.Data analysisIn both control and case groups,the intra-cardiac 2D color Doppler cine loop A4C images of the right atrium(RA),right ventricle(RV),left atrium(LA),left ventricle(LV)in A4C were analyzed with VFM analysis software(DASRS1,Hitachi Aloka Medical Ltd.,Tokyo,Japan).EL was computed from the velocity vector fields of the intra-cardiac blood flow at three phases of the cardiac cycle for each frame of the cine loop image.Statistical analysisWe applied SPSS 19.0 statistical software for analysis that was carried out rather descriptively.All the frameworks were trialed for normal dispension using the Kolmogorov-Smirnov test(K-S test).Constant variables were presented as the mean± standard deviation(SD).The differences between categorical variables were analyzed by the ?2 test.A Paired-Sample T-test was performed to compare the different parameters between control and case groups.Pearson analysis was used to determine the correlation of two variations.ResultsGeneral characteristicsThe demographic and clinical findings(age,gender distribution,HR,B.P.,BMI,BSA,HDL,LDL,TC,and TG)between the control and case groups were similar(all p>0.05).Trans-thoracic echocardiography differences between the control and case groups were significantly found in right and left heart volumes and areas(all p<0.01)but no significant differences were noted in left ventricle ejection fraction,E/A ratio and intra-cardiac diameters(all p>0.05).EL comparisonThe EL levels within the heart chambers such as right atrium(RA),left atrium(LA),right ventricle(RV)and left ventricle(LV)were notably increased at different phases of cardiac cycle such as(s,ed,and ac)in ASD patients(case group)as comparing with the control group.1).RAEL values were significantly decreased during RA(s,ed,and ac)in the control group as compared with the case group(p<0.05).2).RVEL values were diminished prominently during RV(s,ed,and ac)in the control group as compared with the case group(p<0.05).3).LAEL values were reduced markedly during LA(s,ed,and ac)in the control group when compared with the case group(p<0.05).4).LVEL values were decreased during LV(s,ed,and ac)in the control group as compared with the case group(p<0.05).Correlation analysisFor all the ASD patients,the intra-cardiac energy loss(EL)in each heart chamber during different phases of a cardiac cycle such as(end,ac,s)showed statistically significant weak correlations with the right atrium end diastolic volume(RAEDV),right ventricle end-diastolic area(RVEDa),left atrial stroke volume(LASV)and left ventricle ejection fraction(LVEF)respectively.ConclusionVFM is a new technique for imaging blood flow velocity vectors,which has been elaborated to enable the diagnosis of heart disease by using ultrasound to envisage the pattern of blood flow in the heart.It is known as a non-invasive method with the possibility to dispenseextremelyprecise heart disease diagnosis by estimating the velocity vectors,streamline distribution,and vortices distribution of intra-cardiac blood flow.EL quantification using VFM is very helpful to govern the seriousness of diseases from the feature of cardiac load and is more sensitive to reflect the changes of hemodynamic in patients with ASD.