| Sufficient tissue-level reperfusion is crucial for evaluating the efficiency of therapy in patients with acute myocardial infarction (AMI). Early evaluation of myocardial blood flow, prevention and attenuation the"no reflow"phenomenon is important for prognosis of patients with AMI.Coronary flow reserve (CFR) is one of the clinically available methods for evaluating microvascular function. Intracardiac echocardiography (ICE) is a newly introduced technique for imaging proximal coronary arteries. However, whether the flow parameters in proximal coronary arteries were related to myocardial perfusion and infarct size are remained unclear.Salvianolate, an aqueous extract from the Chinese herb"Danshen", is proved to be the major component with cardiovascular benefit. However, whether salvianolate could protect microvascular function in reperfused myocardium has not been clarified. The effect of salvianolate on proximal coronary flow parameters has not been investigated, either.In this study, using a closed-chest model of myocardial ischemia and reperfusion in pigs, we designed to determine whether salvianolate could protect microvascular reflow, and could reduce infarct size and improve left ventricular systolic function. Using ICE, We also aimed to delineate the dynamic changes in the proximal coronary arteries during myocardial ischemia and reperfusion, and to clarify the relationship between coronary flow parameters and myocardial reperfusion or infarct size. In order to partially explain the possible mechanism of the protective effect of salvianolate, we examined the oxidative stress status, the activity of thioredoxin and apoptosis in the infarct area.Myocardial ischemia was induced by balloon occlusion at the midsection of left anterior descending coronary artery (LAD) for 2 hours, and reperfusion was obtained after deflating the balloon. Animals were divided into 4 groups: group I received low-dose salvianolate intravenous treatment (5mg/kg per day for 7 days), group II received high-dose salvianolate intravenous treatment (10mg/kg per day for 7 days), group III received high-dose salvianolate intravenous treatment plus intracoronary injection (20mg salvianolate) five minutes before reperfusion, group IV received normal saline instead of intravenous salvianolate. Myocardial contrast echocardiography (MCE) and colored microspheres were used to measure myocardial perfusion.LV systolic function was determined by transthoracic echocardiography (TTE).Proximal flow parameters were acquired from left coronary arteries at baseline, end of occlusion, 15min, 1 hour, 2 hours and 14 days after reperfusion, both at resting and hyperemia.After reperfusion for 14 days, both Evan's blue and triphenyltetrazolium chloride (TTC) staining were performed to determine risk area and infarct size, respectively.The enzymatic activities of superoxide dismutase (SOD), the level of reduced forms of glutathione (GSH), the level of nitric oxide (NO) and malondialdehyde (MDA) were all measured in the risk area. The activity of thioredoxin (TRX) was detected using insulin reduction assay. The protein expression of Bcl-2 and Bax was measured by Western blot analysis. Apoptosis was also measured by TUNEL staining. Immunohistochemistry was performed to identify endothelial cells and the apoptotic index of endothelial cells and capillary density was calculated.The result showed that high-dose salvianolate (group III and IV) significantly decreased perfusion defect size and increased A×βon MCE after reperfusion, as compared with low-dose treatment group or controls. The reserve ofβand A×βwas also increased in high-dose treatment groups at 14-day reperfusion. The capillary density was increased in all the treating groups, as compared with controls.TTC staining showed that the infarct size was significantly decreased in high-dose treating groups. After 14 days of reperfusion, the anterior septal wall thickening, FAC, and LVEF were all increased in high-dose groups.Using ICE, dynamic changes were detected in the proximal left coronary arteries during myocardial ischemia and reperfusion. CFVR decreased both in proximal LAD and left circumflex artery (LCx) and Left main coronary artery (LMCA) during LAD occlusion and reperfusion. After 14 days of reperfusion, the CFVR in proximal LAD significantly correlated withβreserve in the risk area, or with A×βreserve, or with infarct size(expressed as percent of total LV area)。High-dose intravenous salvianolate plus 20mg intracoronary injection significantly increased CFVR in proximal LAD after 14 days of reperfusion, as compared with other groups.As compared with controls, the enzymatic activities of SOD, the level of GSH, the activities of TRX in the risk area were significantly increased in high-dose salvianolate treating groups. The level of MDA in the risk area was significantly decreased in high-dose treating groups. However, the level of NO showed no significant difference among all the groups. The expression ratio of Bcl-2/Bax in the risk area was significantly increased in high-dose treating groups. Apoptotic cells in the risk area were significantly decreased in high-dose treating groups. TUNEL positive endothelial cells were also significantly decreased in high-dose treating groups.In conclusion, high-dose salvianolate administrated intravenously per day for 7 days can effectively attenuate microvascular dysfunction after myocardial ischemia and reperfusion, resulting in decreased infarct size and improved LV systolic function. The protective effect of salvianolate is partially due to the decreased oxidative stress and endothelial cell apoptosis in the risk area. ICE is an effective new technique for detecting proximal coronary blood flow. After 14 days of reperfusion, the proximal CFVR in IRA reflects myocardial reperfusion status and infarct size. Intracoronary injection of 20mg salvianolate can improve proximal CFVR after 14 days of reperfusion.
|
PDF Full Text Request