Real-Time Three-Dimensional Echocardiographic Study Of Dynamic Morphology Mechanism And Right Ventricular Function Of Atrial Septal Defects

BACKGROUND AND PURPOSE The clinic importance of atrial septal defect (ASD) consist that it is the common cardiac defects of congenital cardiovascular malformation, accounting for 25%-30% of all congenital heart diseases. Real time three dimensional echocardiography (RT 3DE) developments by Duke University has recently been applied in clinical settings. This technique can analyze the 3D geometry and dynamics of the interatrial septum, display the surrounding relationship of ASD on multi-view image, with meticulous measurements of the size and area of defect, which has an important significance about quantization the ASD size, understanding the relationship between cardiac structure and hemodynamics and selection the suitable management.A study of us assessment the dynamic changes of ASD area by RT 3DE which found the ASD area changed significantly during cardiac cycle. ASD area decreased gradually during atrial contraction and the minimum area was reached at end-diastole, then increased gradually during ventricular contraction and the maximum area was reached at end-systole. The dynamic changes of ASD area were related with the changes of atrial pressure and volume and the translation of the atrioventricular valve ring. The advance in RT 3DE may potentially to study the volume of atrial and the translation of the atrioventricular valve ring which may contribute to the mechanism of ASD area. To explain the changes of atrial volume and the translation of the atrioventricular annulus using 3D view may be improved understanding of the relationship between the changes of cardiac structure and hemodynamics. On the basis of elucidate the mechanism of ASD area change which can enhance to know the status of cardiac contraction and relaxation, the relationship between the load of heart and the degree of disease, which may be helpful to selection suitable management in clinic protocols.The left atrium pressure is higher than right atrium with thinner right ventricular wall and better compliance which result in massive left to right shunt in ASD patient. Long term shunt leads to the development of right heart volume overload and affect right ventricular (RV) function to some extent. The accurate evaluation of RV function has a very important clinic application in assessing the disease condition, choosing therapeutic protocol and monitoring therapeutic efficacy and prognosis of ASD patients. Assessment of RV function in ventriculography, radionuclide imaging, cardiac magnetic resonance imaging, or computed axial tomography may not be feasible and practical because of some limitations. Ultrasonography is the most common method to assess cardiac function with its noninvasive, simple and convenient.However, right ventricle has an irregular shape, with a separate infundibulum and prominent trabecular muscles. It's difficult to describe the right ventricle by a simple geometric figure and therefore, difficult to assess its function in a conventional two-dimensional echocardiography. Dynamic three-dimensional echocardiography can evaluate RV volume and function but not extensive application because of its time consume and energy to deal with image.Little is known about the tripartite right ventricular modeling in response to volume overload, such as in ASD, because of the complex RV geometry. Moreover, regional RV volume or function can contribute to global regional RV volume or function and reflect regional disorder of myocardium. Tissue Doppler imaging, strain rate imaging, acoustic quantification and velocity vector imaging is the ultrasound technique for analysis of regional RV systolic function from measure regional myocardium translation and systolic velocity and evaluate regional RV pumping function rarely. RT 3DE overcome limited of ultrasound techniques which mentioned above. It obtained RV volume image quickly and combined with three-dimensional workstation to track endocardium that make a live RV three-dimensional image independent of geometric assumption. There are tripartite with right ventricle from the characteristic of morphology and function. The changes of regional RV volume provide information about regional RV pumping function. This study included four parts as follow:Part 1 Evaluation of interatrial septum dynamics and correlation factor in normal human by real time three-dimensional echocardiographyThe purpose of this part was to investigate dynamic changes of interatrial septum (IAS) and its correlation factor. RT 3DE was performed in normal human using a three-dimensional workstation to obtain the en face view of IAS and measure its area at the peak of P-wave, the peak of R-wave, the initial and the destination point of T-wave, and the period of P-T. Measure right atrial volumes in different time which mentioned above and tricuspid annulus motion (TAM) distance in different correspond time period mentioned above, and have correlation analysis with IAS area. RESULTSâ‘ The IAS area changed significantly during cardiac cycle,which reached a maximum at end-systole and a minimum at end-diastole. The percentage change ranged from 32.3% to 55.8%, with a mean of 50.7%.â‘¡Right atrial volume and the curve of TAM were dynamic changed in cardiac cycle, and the IAS dynamic feature was similar to them.â‘¢IAS area has a good correlation with right atrial volume in different time which mentioned above (r=0.78-0.91). IAS area change has a good correlation with TAM distance (r=0.60-0.73).Part 2 Investigation of atrial septal defect area dynamic mechanism by real time three-dimensional echocardiographyThe purpose of this part was to investigate dynamic changes of right atrial volumes and tricuspid annulus motion (TAM) to determinate the mechanism of ASD area dynamic change. RT 3DE was performed in ASD patients and control group using a three-dimensional workstation to measure defect area and IAS area at the peak of P-wave, the peak of R-wave, the initial and the destination point of T-wave, and the period of P-T. Measure right atrial volumes in different time which mentioned above and TAM distance in different correspond time period mentioned above, and have correlation analysis with ASD area. A comparison results including right atrial volumes, TAM distance and RV function between ASD and control group. RESULTSâ‘ The ASD area changed significantly during cardiac cycle,ASD area decreased gradually with atrial contraction and the minimum area was reached at end-diastole that with the change curve reached the lowest point, then increased gradually during ventricular contraction and the maximum area was reached at end-systole that with the change curve reached the highest peak. The percentage change ranged from 40.4% to 77.2%, with a mean of 60.3%.â‘¡Right atrial volume and the curve of TAM were dynamic changed in cardiac cycle, and the ASD area dynamic feature was similar to them.â‘¢ASD area has a good correlation with right atrial volume in different time which mentioned above (r=0.75-0.80 P<0.001). ASD area change has a negative correlation with TAM distance (r=0.47-0.58, P<0.05).â‘£Right atrial volume in different time of cardiac cycle was higher than result of control group (P<0.001). TAM distance and RV ejection fraction was lower than result of control group (P<0.05).Part 3 Assessment of normal global and regional right ventricular function by real-time three-dimensional echocardiography and its accuracy evaluationThe purpose of this part was to investigate global and regional RV volume or function and verify its accuracy. RT-3DE was performed in 36 healthy individuals. Regional and global right ventricular end-diastolic volume, end-systolic volume and ejection fraction were measured by 4D right ventricular quantitation (4D RVQ) method. The regional parameters in different right ventricular components were compared respectively. The global parameters derived from 4D RVQ were compared with the results of longitudinal Axial 8 plane (LA 8-plane) and Multi-Slice Computed Tomography (MSCT) measurements. RESULTSâ‘ Global RV end-diastolic volume, end-systolic volume and ejection fraction obtained from 4D RVQ method was no statistic significance and correlated significantly with LA 8-plane findings (r=0.96, 0.93 and 0.81 respectively).â‘¡Global right ventricular end-diastolic volume, end-systolic volume and ejection fraction obtained from 4D RVQ method was no statistic significance and correlated significantly with MSCT findings (r=0.96, 0.93 and 0.85 respectively).â‘¢Regional volume is decrease progressively from inlet portion, apical trabecular portion to outlet portion. Regional right ventricular ejection fraction is lower in the apical trabecular portion than the inlet (p<0.05) and outlet portion (p<0.05). Apical trabecular portion ejection fraction was no statistic significance with global measurement (p>0.05).Part 4 Assessment of global and regional right ventricular function in atrial septal defect patients by real time three-dimensional echocardiography: A control studyThe purpose of this part was to study global and regional RV volume or function in ASD patients and compare with normal subjects. RT 3DE were performed in 32 ASD patients (ASD group) and 32 healthy individuals (control group). Some parameters were measured by 4D RVQ method and compared with the two groups. The index include global RV end-diastole or systole volume, regional RV end-diastole or systole volume including inlet, apical trabecular and outlet portions, global RV ejection fraction and regional RV ejection fraction including tripartite which mentions above. The global parameters derived from 4D RVQ were compared with LA 8-plane measurements. RESULTSâ‘ Regional RV ejection fraction is lower in the apical trabecular portion than the inlet, outlet portion and global RV ejection fraction (p<0.05).â‘¡Global RV end-diastolic volume, end-systolic volume and ejection fraction obtained from 4D RVQ method were no statistic significance and have an excellent correlation with LA 8-plane findings, r=0.96, 0.92 and 0.78 (ASD group),r=0.98, 0.96 and 0.87 (control group).â‘¢Global and regional RV end diastolic or systolic volume of ASD patients was higher and apical trabecular portion, global RV ejection fraction was lower than control group (P<0.001). Inlet portion, outlet portion RV ejection fraction was no statistical significant as compared with controls (P>0.05).CONCLUSIONS1 Real time three-dimensional echocardiography can assess dynamic changes of parameters of cardiac spatial structure noninvasive. Interatrial septum dynamic feature was similar to the dynamic curve of right atrial volume and tricuspid annulus during cardiac cycle in normal individual.2 Interatrial septum area was related with the change of right atrial volume and tricuspid annulus motion.3 The ASD area changed significantly and regularity during cardiac cycle. The curve of ASD area was similar to dynamic change of right atrial volume and curve of tricuspid annulus motion.4 The ASD area was related with the change of right atrial volume and tricuspid annulus motion. 5 ASD leads to right atrial volume overload, tricuspid annulus motion decreased and right ventricular dysfunction.6 RT3DE can evaluate global and regional right ventricular volume and function accurately, and the systolic function is difference to each portion of right ventricular in normal which may be related to morphology and function of right ventricular.7 The systolic function is difference to each portion of right ventricular in ASD patients and the global right ventricular function is not represented the change of regional right ventricular function.8 Global and regional right ventricular volume was increased and apical trabecular portion, global right ventricular ejection fraction was decreased in ASD patients. Regional right ventricular pumping function might reflect right ventricular dysfunction.