A Basic Research On Changes Of Coronary Microcirculation In Coronary Heart Disease Using Myocardial Contrast Echocardiography

Objectives:It is now recognized that coronary microcirculation plays an important role in determining myocardial perfusion. However,little advances have been made in the field because of being short of appropriate method. In recent years,myocardial contrast echocardiography (MCE) has been showed the capability in evaluation of microcirculation function. The aims of this study were (1) To develop a new method for quantification of myocardial perfusion with MCE;(2) To evaluate whether the dynamic changes in myocardial perfusion during coronary artery occluding and reopening can be revealed by MCE in real time,and explore the relation between the pulse trigger interval and the risk area measured by MCE;(3) To investigate whether the adaptive changes in intramyocardial blood volume during non-flow-limit coronary stenosis (NFLS) can be detected by MCE at rest without recourse to stress.Methods:1. Methodological research on quantification of myocardial perfusion with MCE by continuous infusion(1) Quanfuxian (a homemade contrast agent consisted of albumin and C3F8) was diluted to 20 folds by normal saline solution and pumped into a femoral vein in 6 dogs with a constant velocity (0.5,1,2 or 6 ml/min). The contrast effect,heart rate,aortic blood pressure,pulmonary blood pressure,pulmonary capillary wedge pressure and ECG before and after MCE were recorded and compared.(2) The trigger interval was lengthened by a cardiac programming stimulator or a self-made trigger-extension apparatus,and stabilities of trigger signals were evaluated.(3) The influence of the trigger setting in different phase of a cardiac cycle on quantification of myocardial perfusion was defined by setting two different phasic trigger (R-wave trigger or T-wave trigger) in 6 dogs. A and P obtained from R -wave trigger refilling curve were compared with which obtained from T-wave trigger refilling curve.2. Experimental study of MCE on risk area evaluation(1) The dynamic changes of myocardial perfusion during LAD occluding and reopening were observed with MCE by continuous infusion of Quanfuxian.(2) Calculated and compared the contrast defect areas acquired with different pulse trigger intervals in LAD occlusion.3. Study on detection of non-flow-limit coronary stenosis at restA screw occluder was placed around the proximal LAD,and a side branch of the LAD was cannulated a 20-gauge catheter for distal coronary pressure measurement. Two levels of NFLS were produced in each dog and stenosis severity was categorized on the basis of the transstenotic pressure gradient (TsPG) as mild (10-25 mmHg) or moderate (26-40 mmHg). Phasic changes in myocardial contrast intensity were measured at rest with continuous high mechanics index (MI) contrast echocardiography. The ratios of systolic and diastolic contrast intensity were compared among the baseline,mild stenosis,and moderate stenosis.Results:1. Methodological research on quantification of myocardial perfusion -with MCE by continuous infusion of contrast(1) There were no significant changes in ECG,"heart rate and hemodynamics before and after continuous infusion of Quanfuxian. Therewas a linear relationship between the contrast video intensity and the rate of contrast infusion (y = 19.137x + 7.9993;R2 = 0.9854;P = 0.0073). The best contrast effect was found in Group of 2 ml/min.(2) There was no difference in video intensity between 3 minutes and 5 minutes after myocardial opacification.(3) The trigger interval could be lengthened to 45 cardiac cycles by using cardiac programming stimulator or a self-made trigger-extension apparatus. All trigger signals were stable.(4) No differences in plateau video intensity or refilling velocity were noted between R-wave and T-wave trigger refilling curve.2. Experimental study of MCE on evaluation of risk area(1) With using MCE,the following phenomenon were observed. During LAD occluding,the contrast in anterior wall was disappeared immediately and the anterior wall became thinner subsequently. During LA...