| Background and aim: Myocardial ischemia and reperfusion play key roles on the process of cardiovascular disease. But current clinical need is still unmet. Photoacoustic imaging technology(PAT) combining optics and ultrasonics has four advantages: high resolution, high contrast, depth scalability and no radiological hazard. And PAT can obtain special photoacoustic signal of hemoglobin. This study aims to explore the feasibility about to vivo detect acute myocardial ischemia(AMI), acute myocardial ischemia/reperfusion(AMI/R) and chronic myocardial ischemia(CMI) in new zealand white rabbits based on PAT.1. Acute myocardial ischemiaMethods: The 42 new zealand white rabbits(2.78 ± 0.23Kg) were randomly devided into acute ischemia group and control group. Left circumflex branch of rabbits were ligated for 0.5h, 1h, 2h, 3h, 4h, 6h in acute ishcemia group and were on sham operation for 6h in control group. 6 rabbits were used on each set time. ECG was examined, blood was drawn for the detection of serum markers of myocardial injury(cardiac troponin-I, c Tn I; creatine kinase isoenzyme, CK-MB), and the gray value and total quantity were obtained by PAT images on each set time. The heart was removed, then the indicators of pathological(semiquantitatively assessed score, SAC; apoptosis index, AI) were obtained by staining with hematoxylin-eosin(HE) and TUNEL apoptosis.Results: The serum markers of myocardial injury and indicators of pathological of the acute ischemia groups showed a trend of increase with the ligation time increasing(P<0.05). But the AI of the ligation 6h group was lower than the one of the ligation 4h group(P<0.05). Both gray value and total quantity of the acute ischemia groups showed a trend of decrease with the ligation time extending(P<0.05). The gray value and total quantity showed that had negative relevance with serum markers of myocardial injury and indicators of pathological, respectively(P<0.05).Conclusion: Our results showed that the myocardial ischemia injury was much more serous with ischemia time extending; the gray value and total quantity had inversely relevance with myocardial ischemia injury, respectively. Hence, PAT is a valuable method to assess AMI within AMI 6h.2. Myocardial ischemia/reperfusionMethods: The 24 new zealand white rabbits(2.77 ± 0.24Kg) were used in reperfusion group. Left circumflex branch of rabbits were opened for reperfusion 0.5h, 1h, 2h and 4h after occlusion of 2h, respectively. Every 6 rabbits were randomly used on each reperfusion time. ECG was examined, blood was drawn for the detection of serum markers of myocardial injury, and the gray value and total quantity were obtained by PAT images on each reperfusion time. The heart was removed, then the indicators of pathological were obtained by staining with HE and TUNEL apoptosis. And the results of ligation 3h, 4h and 6h were compared with reperfusion 1h, 2h and 4h, respectively. The sham operation 6h group and ligation 2h group were set as control group.Results: The serum markers of myocardial injury and indicators of pathological of the reperfusion groups showed a trend of increase as the reperfusion time extending(P<0.05). But the AI of the reperfusion 4h group was lower than the one of the reperfusion 2h group(P<0.05). However, the serum markers of myocardial injury and SAS of the reperfusion 4h group were lower than those of the ligation 6h group(P<0.05); the AI of the reperfusion 4h group was higher than the one of the ligation 6h group(P<0.05). The gray value and total quantity of the reperfusion groups increased with the reperfusion time increasing(P<0.05). And the gray value of the reperfusion 4h group compared with the sham operation 6h group, there was not statistically significant difference(P>0.05); the total quantity of the reperfusion 4h group was lower than the one of the sham operation 6h group(P<0.05). The gray value and total quantity showed that had positive correlation with the serum markers of myocardial injury and indicators of pathological, respectively(P<0.05).Conclusion: Our results showed that the myocardial injury was much more serious with the reperfusion time increasing. But the extent of increase in the reperfusion group was lower than that in the ligation group. The gray value and total quantity had positive correlation with AMI/R injury. The total quantity did not return to the normal level after reperfusion 4h, which might be due to no-reflow phenomenon. Hence, PAT is a feasible way to evaluate AMI/R within reperfusion 4h after occlusion 2h.3. Chronic myocardial ischemiaMethods: The 13 new zealand white rabbits(2.60±0.20Kg)were randomly devided into experimental group(n=10) and control group(n=3). Ameroid constrictors were implanted on the surface of left circumflex in experimental group and were not implanted in control group. The TIMI flow grade was employed to assess myocardial perfusion after coronary arteriongraphy(CAG) in the 5th week. TIMI grade 0~1 was set as infarction group and TIMI grade 2~3 was set as chronic ischemia group in experimental group. Blood was drawn for the detection of serum markers of myocardial injury and the gray value and total quantity were obtained by PAT images after median sternotomy. Then the hearts were stained by HE.Results: The serum markers of myocardial injury of the infarction group(n=4) were higher than those of the chronic ischemia group(n=3) and the control group(n=3)(P<0.05). There was a high rank correlation between total quantity and TIMI myocardial perfusion grade( r: 0.849; P<0.05).Conclusion: Our results showed that the CMI model could be built by implanting ameroid constrictors into rabbits. And PAT is a valuable method to assess the CMI.In summary, our results suggest great potential for this new imaging tool for detecting AMI, AMIR and CMI. Though there are still many shortcomings in our research, but PAT is worth furtuer study. |
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