| BackgroundCAD(coronary atherosclerotic heart disease), also called coronary heart disease, is a condition in which plaque builds up inside the coronary arteries. These arteries supply your heart muscle with oxygen-rich blood. It is now one of the leading causes of death all over the world. Ischemia is the basic pathophysiological change happened in coronary artery disease. The onset of ischemic symptom and its development, the lasting time for the ischemic strike and the recovery of reperfusion vary in every one of the different CAD patients, leading to differences in myocardial morphology, myocardial metabolism and myocardial function in every CAD patient. It is reported that the time when left ventricular function changed is much earlier than previously predicted, which was closely associated with atherosclerosis of the coronary arteries. Left ventricular function and its regional myocardial systolic and diastolic function have intimate relationship with the patient's prognosis, cause both the systolic and diastolic function can have a direct influence on the dynamics of blood flow in the heart chamber and human body. Therefore, if we can quantitatively accurately and sensitively assess the regional myocardial function,detect the abnormal myocardial segment at its early stage, the evidences for CAD diagnosis, the choices for treatment and the prognosis for patients will be much more valid and reliable, which is of great importance in clinical practice.Until now, the study of regional infarct and ischemic myocardial function is still mainly focused on the abnormal wall motion, and there is little report about how the blood flow affected by the regional abnormal wall motion in CAD patients is.Vector Flow Mapping (VFM) is a new method for measuring blood flow vector and is based on Echo-Dynamography which measures various cardiac function. By using VFM, we can measure speed and direction of blood flow by estimating the velocity component in the direction which is perpendicular to the direction of the ultrasound beam. It can show the magnitude and direction of the blood flow within the cardiac chamber by vector profile, while the vortex can be shown by stream-line profile. It can evaluate the blood flow pattern timely, precisely and quantitatively, which can be a prospective way to better understand the complex flow pattern in our human body. In our study, the Vector Flow Mapping technique is used to investigate the blood flow pattern adjacent to the regional myocardial segments in CAD patients.Velocity vector imaging (VVI) technique, a novel echocardiographic technique independent of Doppler principle, is based on two-dimensional gray-sale images and thus angle-independent in principle.VVI can track speckles we draw on the endocardium frame by frame accurately, provide angle-independent 2D velocity, strain, and SR,get information about the movement of wall motion and thus can be used to quantitatively assess regional myocardial function. It is reported that systolic peak strain(Ss)≥-14% can reflect the abnormal wall motion in ischemic myocardium in CAD patient, while systolic peak strain(Ss)≥-6.5% can reflect the abnormal wall motion and reduced systolic function in infracted segments.Objective(1)To explore the dynamic changes happened in the regional heart chamber with VFM technique.(2) To investigate the blood flow dynamics adjacent to the regional ischemic and infarct myocardial segments in CAD patients by using Vector Flow Mapping (VFM) technique and Velocity Vector Imaging (VVI) technique, and to explore the correlation between the blood flow dynamics and wall motion;(2) To explore sensitive indexes showing blood flow dynamics change caused by abnormal wall motion in CAD patients.Methods 1.Study population43 CAD patients (29 male,14 female, average year is 56.32±18.14) were enrolled in our study. All patients took auxiliary examinations as follows ECG, echocardiography and cTnI detection and were excluded from the diagnosis of valvular heart disease, cardiomyopathy and arrhythmia.12 of them suffered from myocardial infarction and the rest 31 suffered from myocardial ischemia.2.Methods2.1 EchocardiographyALOKA a-10 ultrasound machine with broad-spectrum transducer in 1.5～5.0 Hz was used to acquire VFM data in the patients. Patients were lying at left recumbent positions, with ECG monitored. Images of apical four, two-chambers and long-axis view were obtained in VFM condition with frequency kept at29-31Hz. Data were analyzed with DAS-RS1 offline software.Siemens Sequoia 512 ultrasound machine and 4V1C transducer in 2-4MHz was used in our study. Patients were lying at left recumbent positions, with ECG monitored. Two-dimensional images of apical four-, two-chambers and long-axis view were obtained in VVI condition and with frame rate kept 70-100Hz. All the data were analyzed with Syngo US workplace software.2.2 Data processingThe left ventricle is divided into 18 segments, every wall is divided into basal, middle and apical segments.VFM data were analyzed with DAS-RS1 offline software. Threshold were set at 95,and regions of interest were adjusted. A 1cm long line was laid in the chamber vertical to endocardium adjacent to regional segment. Data were obtained in Time-Flow pattern. The indexes including Q+, Q-, Q total, systole Q+, systole Q-, diastole Q+, diastolic Q-,Al,A2, T1 and T2 were analyzed in one heart cycle.VVI data were analyzed with Syngo US workplace software. The indexes included peak systolic velocity (Vs), early diastolic velocity (Ve), late diastolic velocity (Va), ratio of diastole and systole velocity (Ve/Va), peak systolic strain (Ss), peak systolic strain rate (SRs), early diastolic strain rate (SRe), late diastolic strain rate (SRa),ratio of diastole and systole strain rate (SRe/SRa),segmental ejection fraction (SEF)3.Statistical analysisSoftware SPSS (version 16.0) was used for statistical analysis. All VFM results are expressed as mean±standard deviation (SD). Differences between the two groups were tested by two-sample t-test for independent sample, and the correlations among indexes derived from VFM and VVI were done by Pearson coefficients.All tests were 2-sided and P≤0.05 was considered significant.Results1.General statesAmong the 43 CAD patients,560 segments with satisfactory clip image are suitable for analysis. There are 158 ischemic segments and 402 normal segments, while the number for infarct segments is 36, and the rest 524 segments are of no infarction.2.Differences of VFM indexes between ischemic segments with obvious abnormal wall motion and normal segments with relative normal wall motion in CAD patients.Compared to normal segments, Q+,Q-,Q total, systolic Q-and diastolic Q-tend to decrease.with the possibilities reach 0.075,0.442,0.137,0.508 and 0.406 respectively. Systolic Q+ is higher in abnormal group (P=0.008), while diastolic Q+ is lower in abnormal group(P=0.000),compared to normal group. T1 tends to prolong, while T2 is significantly shortened in abnormal segments (P=0.000).The tendency for al to decrease is slower, while the tendency for a2 to increase is faster in abnormal segments compared to normal segments.3.Differences of VFM indexes between AMI segments with obvious abnormal wall motion and its adjacent segments with relative normal wall motion in CAD patients.Compared to normal segments,Q+ tends to decrease in abnormal segments (P=0.188); while Q-,Q total,systolic Q- and diastolic Q- tend to increase, with the possibilities reach 0.145,0.764,0.130 and 0.244 respectively. Systolic Q+ is higher in abnormal group (P=0.021),while diastolic Q+ is lower in abnormal group(P=0.002), compared to normal group. T1 tends to prolong, while T2 is significantly shortened in abnormal segments.The tendency for al to decrease is slower, while the tendency for a2 to increase is also slower in abnormal segments compared to normal segments.4.Correlation between indexes derived by VFM and VVIThere is a significant negative correlation between Q+ and Ve(r2=0.208, Pearson Correlation=-0.456,P=0.013);There is a significant positive correlation between systolic Q+ and Ss(r2=0.188, Pearson Correlation=0.433,P=0.024);There is a significant negative correlation between systolic Q+ and SEF (r2=0.196,Pearson Correlation=-0.443,P=0.021);There is a significant positive correlation between systolic Q-and Ss(r2=0.162, Pearson Correlation=0.402,P=0.028);There is a significant positive correlation between systolic Q-and SRs(r2=0.164, Pearson Correlation=0.405,P=0.027);There is a significant negative correlation between diastolic Q+ and Ve(r2=0.235, Pearson Correlation=-0.485,P=0.008);There is a significant negative correlation between diastolic Q+ and Va(r2=0.142, Pearson Correlation=-0.377,P=0.044);There is a significant positive correlation between diastolic Q+ and Ve/Va (r2=0.204,Pearson Correlation=0.451,P=0.016);There is a significant positive correlation between diastolic Q-and Ve(r2=0.204, Pearson Correlation=0.451,P=0.014);There is a significant negative correlation between diastolic Q-and Ve/Va (r2=0.248,Pearson Correlation=-0.498,P=0.006);There is a significant negative correlation between diastolic Q-and SRe/SRa (r2=0.153,Pearson Correlation=-0.391,P=0.036)There is a significant positive correlation between A1 and Ss(r2=0.158, Pearson Correlation=0.398,P=0.03);There is a significant negative correlation between A1 and SEF(r2=0.229, Pearson Correlation=-0.478,P=0.08);There is a significant negative correlation between T1 and SEF(r2=0.247, Pearson Correlation=-0.497,P=0.005);There is a significant positive correlation between A2 and SRe(r2=0.16, Pearson Correlation=0.4,P=0.035);There is a significant positive correlation between A2 and SRa(r2=0.201, Pearson Correlation=0.448,P=0.022);There is a significant negative correlation between T2 and Ve(r2=0.199, Pearson Correlation=-0.446,P=0.02);There is a significant positive correlation between T2 and Ve/Va(r2=0.19, Pearson Correlation=0.435,P=0.023);There is a significant positive correlation between T2 and SRe(r2=0.264, Pearson Correlation=0.514,P=0.004);There is a significant positive correlation between T2 and SEF(r2=0.285, Pearson Correlation=0.534,P=0.004).Conclusions1.Reduced systolic function of regional myocardium can influence its adjacent blood flow dynamics. Significant differences are observed in systole Q+,diastole Q+ and T2 between reduced systolic function segments and normal segments of regional myocardium.2.VFM can be used to evaluate the abnormal wall motion in CAD patients by calculating the blood flow dynamics. Systole Q+ is a better index, when the cutoff value reaches 25.32 and 28.046, it has a high sensitivity and specificity for differentiating ischemic and infarct segments.
|
PDF Full Text Request