Effect Of The Cycle Time Of Myocardial Ischemic Postconditioning On Primary Percutaneous Coronary Intervention In Patients With Acute Myocardial Infarction

BACKGROUNDOn the basis of coronary artery disease,if coronary artery blood flow occurs slowly or interruptedly and persistently,severe acute ischemia,even myocardial necrosis can happened in the corresponding myocardium,we define this as AMI,short for acute myocardial infarction.On clinic,it usually divides into ST-elevation myocardial infarction (STEMI) and non ST segment elevation myocardial infarction (NSTEMI). AMI threat seriously to human life and health with its high morbidity and mortality,by reason of the fast-paced life,population-aging trends,changing eating habits and social psychological factors,the incidence of AMI were rising year by year in our country.In the past several decades,the mortality of AMI declined obviously with the development of the reperfusion therapy and the understanding of its essence,but its fatality rate is as high as 11.9%.Chinese PEACE group conducted a 10-year retrospective study of STEMI showing that hospitalization rates of patients with STEMI rised,the associated comorbidity and intensity of detection and treatment increased, utilization rate of primary PCI ascended,however,the proportion of patients having not undergone PCI had not changed significantly, hospital mortality did not fall.To patients with acute STEMI, primary PCI can open the infarction related artery (IRA) and restore the IRA blood flow timely, effectively and sufficiently, which is recommended as the first choice by the American college of cardiology/American heart association (ACC/AHA) guidelines. However,the rapid recanalization of blood flow can bring heart structure and function with more serious damage, usually called ischemia-reperfusion injury, when and how to do has been the research focus in recent years. Zhi-Qing Zhao etal confirmed the myocardial protection of ischemic postconditioning(IPOC) in the ischemic reperfusion model of dogs in 2003. Subsequently,drugs postconditioning,mechanical postconditioning and ischemic postconditioning can all be confirmed effective in reducing the myocardial infarction area and improve heart function. Nonetheless, the specific mechanism of IPOC has not been thoroughly studied, the precise operation timing and selection are unclear, in addition,it failed to enter the large-scale clinical application.OBJECTIVE:By investigating the impact of different cycle time of myocardial ischemic postconditioning on the myocardial infarction area, reperfusion blood flow and cardiac structure and function of patients undergoing primary percutaneous coronary intervention, to further identify the myocardial protective effect of IPOC and to assess the better IPOC cycle time.METHODS100 patients with acute ST-elevation anterior infarction were randomly assigned to four groups:the control group (n=25) received conventional PCI, as well as having not been accepted any intervention measures; the first postconditioning group (n=25) underwent 3 cycles of repetitive balloon deflation and inflation with low pressure(4-6atm) one minute after opening the anterior descending, every cycle lasted 30 seconds,after that,the performer decided whether it need to implant stent;the second postconditioning group (n=25) treated with the same operation, however, the first cycle lasted 30 seconds, the second lasted 60 seconds, the third lasted 90 seconds, whether it need stent implantation was determined by the performer after the operation; the last postconditioning group (n=25) performed within 1 minute of reflow by 3 cycles of 1-minute inflation and 1-minute deflation of the angioplasty balloon,the operator decided the necessity of stent.Blood sampling for the creatine kinase isoenzyme MB (CK-MB)、Cardiac Troponin I (cTNI) and high sensitive C-reactive protein (hs-CRP) were taken at predetermined time after PCI. Corrected Timi Frame Count (CTFC) was calculated by two senior interventional experts. All patients received Doppler ultrasound examination and rest 9 mTc-sestamibi (99mTc-MIBI) myocardial perfusion singlephoton emission computed tomography (SPECT) seven days and there months after PCI. Finally we compare the serum enzymology, CTFC, cardiac structure and function indicators, SPECT score of four groups to induce the difference between groups is statistically significant or not.RESULTS1.The peak(CK-MB) and the cTNI concentration 72 hours after PCI of the second postconditioning group were lower than the control group,the first postconditioning group and the last postconditioninggroup(Peak-CK-MB:126.6+9.0 ng/ml,52.9± 7.3ng/ml,89.5±7.3ng/mlvs.166.9±11.9ng/ml, P<0.05;72h cTNI:12.5±1.9 ng/ml, 5.7 ± 1.6ng/ml,7.5±2.1ng/ml vs.16.8±2.3ng/ml,P<0.05). No differences were observed in the hs-CRP concentration before PCI among the four groups,but the hs-CRP concentration at 24 hours after PCI was lower in the second postconditioning group compared with the others(P<0.05).2.The CTFC of the second postconditioning group significantly reduced as compared with the control group,the first postconditioning group and the last postconditioning group(21.1±3.5,28.9±5.7,25.1±2.4 vs.24.8±4.3, P<0.05).3.At 7 days after PCI, the LVEDD, Ea/Aa and LVEF of the four groups had no significant difference(P>0.05).At 3 months, no statistical differences were found in the LVEDD of the four groups, nevertheless, the LVEF and Ea/Aa of the second postconditioning group significantly increased compared with the others [LVEF:(59.30±4.32)%, (51.50±4.60)%, (55.30±4.57)%vs.(55.40±3.03)%, P<0.05; Ea/Aa:1.41±0.15,1.03±0.14,1.25±0.18 vs.1.27±0.14, P<.05].4. At 7 days after PCI, the SPECT score of the second postconditioning group was the lowest(14.80 ±2.40,20.00±2.31,17.60 ±2.55 vs.17.50 ±2.99, P<0.05).Similarly, at 3 months, the SPECT score of the second postconditioning group was the lowest(9.20±2.57,14.50±2.37,12.00±2.00 vs.11.90±2.56, P<0.05).The SPECT score was significantly lowered in each group 3 months after PCI in comparison with the corresponding group 7 days after operation(all P<0.05).CONCLUSIONMyocardial ischemic postconditioning can dramatically decrease myocardial infarction size, attenuate myocardial ischemic reperfusion injury and impove cardiac function, in which the asymptotic one can play the best role.