| BackgroundCoronary artery disease（CAD）is caused by the atherosclerosis and plaque formation in the coronary arteries.The diseased blood vessels can undergo spasmodic contraction,plaques fall off and block the coronary arteries,which can reduce the blood supply.The most affected of patients with CAD is left ventricular function.Therefore,the accurate evaluation of left ventricular function in patients with CAD can not only help CAD diagnosis,but also help to predict its curative effect.Two-dimensional speckle tracking imaging（2D-STI）[1]records the motion trajectory of small spot-like strong echoes in the myocardium frame by frame,and reconstructs the real-time motion and deformation of myocardium.It can also quantify the local functions of myocardium（the longitudinal strain of 17 or 18segments）and assess the segmental deformation of the myocardium from multiple directions.2D-STI not only has the benefits of objectivity and independence from angle,but also quantifies myocardial motion in longitudinal,radial and circumferential directions.In this way,the influence of motion of surrounding tissues on myocardial motion can be minimized.2D-STI provides a novel quantitative method for tracking the global and local myocardial motion.Longitudinal myocardial strain has drawn an increasing attention due to its high diagnostic sensitivity to lesions[2,3].It has been shown that 2D-STI parameters such as longitudinal,radial and circumferential strains are more sensitive to myocardial ischemia in patients with CAD than conventional echocardiography.Moreover,the sensitivity of longitudinal strain to myocardial ischemia is higher than that of radial and circumferential strains[4].Global longitudinal strain（GLS）in 2D-STI is defined as the relative change of LV myocardial length between end-diastole and end-systole:GLS（%）=（MLs-MLd）/MLd.Here ML is the myocardial length at end-systole（MLs）and at end-diastole（MLd）.Because MLs is smaller than MLd,GLS is a negative value.ObjectiveTo explore the clinical application value of two-dimensional speckle tracking imaging（2D-STI）in the assessment of left ventricular（LV）myocardial systolic and synchronicity pre and post coronary artery bypass graft（CABG）in patients with CAD.MethodsForty-seven patients with CAD scheduled for CABG were recruited,along with fifty controls without CAD.The images of apical four,two and three chamber views were collected before CABG and at 1 week,1 month,3 months and 6 months after CABG,respectively.The global layer-specific longitudinal peak strain at subendocardium（GLPSendo）,the global layer-specific longitudinal peak strain at middle layer（GLPSmid）,global layer-specific longitudinal peak strain at subepicardium（GLPSepi）and peak strain dispersion（PSD）were determined for 17segments of LV using Echo PAC workstation software and Q-analysis software,then the global layer-specific longitudinal peak strain（GLPS）can be figured out.The difference of these parameters was compared between the groups.Results1.Comparison of baseline data and parameters of conventional echocardiography1.1 The two groups showed no significant difference in smoking history,diastolic blood pressure,peak E,and peak A（P>0.05）.The body mass index（BMI）and systolic blood pressure were higher in the CABG group than in the control group,and the LVEF was lower than the control group,with significant difference（P>0.05）.1.2 Comparison of heart rate:The heart rate of the CABG group was significantly higher at 1 week and 1 month after surgery than the control group（P<0.05）.The heart rate was significantly higher at 1 week after surgery than before（P<0.05）.The heart rate at 3 months and 6 months after surgery was significantly lower than before surgery（P<0.05）.2.Comparison of strain parameters across the layers of LV myocardium2.1 The strain of LV from GLPSendo,GLPSmid to GLPSepi showed a decreasing trend significantly in each group（P<0.05）.2.2 As compared with the control group,the absolute values of GLPSendo,GLPSmid,GLPSepi and GLPS decreased significantly in the CABG groups（P<0.05）.2.3 As compared with the preoperative values,the absolute values of GLPSendo,GLPSmid,GLPSepi and GLPS decreased significantly at 1 week and 1 month after CABG（P<0.05）.The absolute values of GLPSmid,GLPSepi and GLPS increased significantly at 6 months after CABG（P<0.05）;however,there was no significant difference in the absolute value of GLPSendo（P>0.05）.Neither was there significant difference in the absolute values of GLPSendo,GLPSmid and GLPSepi at 3 months after CABG（P>0.05）.3.Comparison of parameters across the left ventricular synchronicityAs compared with the control group,the absolute values of PSD increased significantly in the CABG groups（P<0.05）.As compared with the preoperative values,the absolute values of PSD decreased significantly at 1week,1 month,3months and 6 months after CABG（P<0.05）.4.The analysis of correlation4.1 Pearson correlation analysis showed that GLPS of the CABG groups was negatively correlated with LVIDd and LVIDs（r=-0.543,r=-0.631,P<0.05）,while was positively correlated with LVEF（r=0.708,P<0.05）.There were no correlation between PSD and LVDId,LVIDs and LVEF.4.2 According to Spearman rank correlation analysis,there was no correlation between the PSD of the two groups and their GLPSedo,GLPSmid,GLSSepi and GLPS（P>0.05）,except that the PSD was negatively correlated with GLPSmid and GLPS at preoperative in this study（r=-0.355,-0.365,P<0.05）.Conclusions1.STI technology provides a quantitative evaluation of LV systolic function and synchronicity of myocardial function recovery from ischemia to reperfusion,and it has a good correlation with LVEF in the evaluation of LV systolic function sensitively.2.As a new parameter to evaluate the synchrony of left ventricular systolic in patients with CAD,PSD can evaluate the improvement of left ventricular systolic synchrony after CABG sensitively,simply,accurately,and effectively.And PSD has a good value of promotion in clinical. |
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