| BackgroundCardiovascular complications, particularly perioperative myocardial infarction/injury, seem to be major contributors to mortality after noncardiac surgery. With surgical procedures being very frequent, perioperative myocardial injury is common in clinical practice. Over 80% of patients experiencing perioperative myocardial injury show no obvious symptoms. Therefore perioperative myocardial injury remains undiagnosed and untreated. Moreover, its silent presentation results in limited awareness among both clinicians and the public. Despite being largely asymptomatic, perioperative myocardial injury increases 30-day mortality nearly10-fold.In the perioperative period, the patient is in sedation, which largely covers the clinical symptoms of myocardial injury, moreover,the physical discomfort caused by surgery may also affects the screening of cardiovascular symptoms. Therefore, to strengthen the perioperative monitoring of cardiovascular system, to detect the early sensitive indicators of myocardial ischemia, can improve the detection rate of cardiovascular events and assess the level of coronary reperfusion.PurposeBiomarkers can be measured easily as a part of routine clinical blood draws. Glycogen phosphorylaseBB(GPBB),the key enzyme of glycogen decomposition, constituting glycogen complex in cardiac sarcoplasmic reticulum.Its activation in myocardial ischaemia is a result of an increased glycogen degradation, which changes the constitution of the complex,facilitating clinical detection of emergency. The purpose of this study was to evaluate the value of GPBB in the diagnosis of myocardial injury by analyzing the continuous concentration changes in serum,especially within three hours, in a porcine myocardial ischemia model.MethodsMale Bama pigs underwent ligation of the left anterior descending coronary artery to make miniature pig model of myocardial injury and necrosis. The experiment set up ischemia reperfusion group and ischemia without reperfusion group.GPBB mainly exists in brain and heart tissue when glycogen phosphorylase isoenzyme GPMM exists in muscle tissue, therefore, GPBB send at different time points after coronary artery ligation is released from myocardial cells, excluding surgical reasons. So sham is not set up, but 0h was set up before coronary artery ligation, facilitate compared by different time points after ligation.Bama pigs(n=30)were randomly divided into two groups, 1 hour ischemia and reperfusion 6 hours(I 1h-R 6h) group(n=20), ischemic 7 hours(I 7h) group(n=10). Under general anesthesia, Blood pressure,ECG,pulse oximetry were monitored. Open the chest, fully exposing the heart, the left anterior descending coronary artery was ligated in the lower third. In I 1h-R 6h group ligature is released after one hour followed reperfusion, I 7h group without reperfusion, ECG changes were observed. When the miniature pig was well, chest was closed layer by layer, anesthesia recovery was implemented. After thoracotomy, blooded once from venous before ligation, denoted 0h, then blooded at 0.5h, 1h, 2h, 3h, 5h and 7h after ligation time. Seven time points totaliy, 3-5ml everytime, The supernatant was obtained by centrifugation and immediately put into-80 ?refrigerator frozen. Serum was taken to hospital laboratory,cTnI concentration was detected by fixed laboratory physician. the concentration of GPBB was measured by enzyme linked immunosorbent assay(ELISA). 7h later, the animal was sacrificed. Heart was immediately removed,rinsed with ice-cold phosphate buffer saline(PBS), placed in- 40 ?refrigerator frozen 1 h.The heart was taken into 2mm thick slices from the apex to the bottom, perpendicular to the long axis when it was harden enough,then immers-ed into 1% 2, 3,5-triphenyl tetrazolium chloride(TTC) in phosphate buffer saline, placed in 37 constant temperature water bath for ?30 mins.Pictures was taken by a digital camera at last.Results1.Miniature swine model of myocardial ischemia has been successfully established. In I 1h-R 6h group,twe died from ventricular fibrillation,one died from asphyxia due to airway blockage.In I 7h group, one died from intraoperative ventricular fibrillation, and another postoperative.2.ECGchanges,ST-depression was monitored after ligation, and then rise, showing the typical performance of myocardial ischemia.3.When stained with TTC, normal myocardium was red,while the infarction was pale.Successful establishment of myocardial infarction model has been verified.4. The trends of cTnI concentration in serum is different in different times in both of the two groups(P <0.001). It shows relatively significant difference(P <0.001) between the two groups. And compared to 0h, in I 1h-R 6h group troponin increased significantly in 2h(P <0.05), in I 7h group it slowly increased after 3h, statistically significant(P <0.05) appeared after 5h.5. The trends of GPBB concentration in serum is different in different times in both of the two groups(P <0.001),There was no difference(P> 0.05) between the two groups. And compared to 0h, in I 1h-R 6h group GPBB concentration significantly increased in 1h(P <0.05), decreased in 2h, rised again in 3h,then fell to the normal level.The trends in I 7h group is similar to I 1h-R 6h group.Conclusions1. In porcine model of myocardial ischemia,GPBB concentration in serum was significantly increased after 1 hour ischemia,earlier than troponin I.2. Continuous cTn I and GPBB assay can be applied for early diagnosis of myocardial ischemia. |
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