Study Of Left Heart Remodeling And Integrated Backscatter Of Myocardium After Coronary Artery Bypass Grafting By Echocardiography

Objects:The aim of the study was:l) to explore the structural and functional changes of left ventricle systolic function after surgical revascularization in patients with coronary arterial disease. 2) to assess the diagnostic value of identifying viable myocardium by means of ultrasonic tissue characterization. Methods:32 patients with coronary stenosis of left anterior descending branch and qualified for CABG on left anterior descending branch were enrolled in the study. Echocardiographic examination was performed before operation and 4 times after CABG (2-6 weeks,3 months,6 months and 1 year). Left ventricular systolic function (EF,Fs),diameters and volumes of left atrium and ventricle (LAV,LW),MR(mitral regurgitation) and wall motion score index(WMSI) were measured. Six patients with left ventricular aneurysm underwent aneurysmectomy during CABG. The effect of aneurysmectomy on left ventricular remodeling was studied. We use the short axis view in papillary muscle level to obtain the 2-D image and M-mode image for measuring thickening,motion and percent wall thickening of left ventricular anterior wall. The backscatter data was collected in the integrated backscatter mode and the images and data sets were stored in the optic disc for off-line analysis. The calibated average value of IB,the patterns of IB curves and the magnitude of the cyclic variation of integrated backscatter(CVIB) in left ventricular anterioar wall were measured. With the restoration of wall motion after CABG as "gold standard ",the sensitively and specificity of parameters obtained from ultrasonic tissue characterization for identifying viable myocardium were evaluated. Results:During each of the five echocardiographic examinations the values of LVEF did not differ in patients with LVEF >50% before operation . However,in patients with lower LVEF(<50%),the values of LVEF improved significantly (p<0.01). Mitral regurgitation decreasedsignificantly after CABG (PO.05). LAV LW were not significantly different before and after CABG (P>0.05). LAV LW were significantly reduced after aneurysmectomy. The wall motion and percent wall thickening of left ventricular anterior wall unproved after CABG . Before operation,the %IBS of left ventricular anterior wall with coronary stenosis were higher than left ventricular posterior wall without coronary stenosis and the CVIB of left ventricular posterior wall without coronary stenosis. The CVIB and the pattern of IBS in the zone with wall motion restoration after operation were significantly different form that with non-restoration. But the %IBS did not show significant difference between the two zones. The sensitivity and specificity of IB curve score 2 and CVIB 3.8dB for identifying viable segments were 90% and 71.4%,respectively. Conclusions:The results imply that CABG cab improve LV systolic function and papillary function and ameliorate left ventricular structural remodeling. Myocardial viability can be predicted by the parameters of IBS from UTC in wall motion abnormal segment,which carries potential in improving the outcome and reducing the complications of surgical revascularization.