Outcomes And Risk Factors Of Elective Percutaneous Coronary Intervention For ST-segment Elevation Myocardial Infarction

Background:The primary therapeutic goal in STEMI is to achieve early myocardialreperfusion. Early reperfusion emphasizes the patency of the IRA as early as possible.The reperfusion paradigm postulates indeed that early reperfusion (<12h) results insalvage of myocardium at risk with preservation of both regional and global leftventricular function, with ensuing improvements in long-term survival. Primary PCItherefore has become the choice of treatment for STEMI patients. In the United Statesand some European countries such as Britain, Switzerland, the proportion ofperforming primary PCI has reached70-90%. Unfortunately, administration of PCI isoften not possible within the evidence-based timeframe, especially in developingcountries with less availability both the service and expertise. According to theregistered PCI cases from the Ministry of Health, only3-5%per year in patients withSTEMI treated with primary PCI in China. Meanwhile, about7%-10%per year ofSTEMI patients underwent elective PCI. As the number of annual new onset STEMIis about500,000-600,000, it could estimate that each year about35,000to60,000cases of STEMI patients undergoing elective intervention, which is a fairly largenumber. Current practice guidelines recommend: only patients manifestingspontaneous or inducible myocardial ischemia or hemodynamic instability (such ascardiogenic shock or severe heart failure) are immediately feasible for PCIirresponsive of delayed time from onset. The benefits of routine, i.e.,non–ischemia-driven, PCI of an angiographically significant stenosis in a patentinfarct artery>24hours after STEMI are less well established, and routine PCI of atotally occluded infarct artery>24hours after STEMI should not be undertaken inclinically stable patients without evidence of severe ischemia.The “open artery hypothesis” speculates that restoration of anterograde bloodflow to the peri-infarct area is beneficial to the myocardium even late and beyond thetime limit set for salvage from myocardial necrosis. However, OAT showed high rates of procedural success with PCI and sustained patency but no clinical benefit during anaverage3-year follow-up with respect to death, reinfarction, or heart failure, contraryto the hypothesis. Moreover, a trend toward an excess risk of reinfarction in the PCIgroup aroused concern. A meta-analysis suggested that this controversy might berelated to the differences of study design. For example, SWISSI-II randomized onlypatients with proven silent ischemia on stress testing, whereas the OAT excludedthose patients with post-infarction angina and/or moderate to-severe ischemia. Thisanalysis suggests, indeed, that studies that did not exclude patients with ischemiashowed a greater benefit from late PCI. However, one-third to two-thirds of patientshave residual symptomatic or silent ischemia after AMI, and there is some debate onwhether the OAT study is representative of real life treatment scenarios. Recruitmentin the OAT study was indeed difficult and interrupted early: only2patients per yearper center were enrolled on average representing a very small minority of patients.Therefore, the possibility of implementing a larger randomized controlled trails (RCT)studies and without highly-selected patients has been minimal, especially primary PCIbeing generally used in developed countries.In order to overcome the disadvantage of RCT such as “internal authenticity goodbut external poor” due to highly-selected patients and strictly-controlled medication,real-world (outcome) research is gradually carried out as the improvement of dataprocessing. To analyze “big data” from the real world, current outcome researchescontribute to the outcomes for a certain clinical intervention. Our study also used themethod of real world research to reflect the current situation and prognosis of electivePCI in China. It would have important implications for future development ofguidelines on the reperfusion therapy selection of stable post-MI patients, as well asfor the design of future clinical trials.Objective:The present study aimed to observe the current situation of performing electivePCI for stable patients post-STEMI without early reperfusion treatment and to analyzethe effectiveness of the timing and individual ischemic condition on elective PCI.Methods:In the Part I and II, we constructed a prospective cohort collecting data from theBeijing Monitoring System for Cardiovascular Diseases, which obtained primaryhealth data from two registries: the Beijing Hospital Discharge Information System and the Beijing Vital Registration Monitoring System. All STEMI patients withoutearly reperfusion during2007-2010in Beijing were investigated, excluding patientswith cardiogenic shock, New York Heart Association class III or IV heart failure,ventricular arrhythmias, cancer or renal failure. Multiple Cox regression models andgeneralized estimation equations were used to evaluate the incidence of major adversecardiovascular events (MACEs). In the Part III, we involved a part of patients toevaluate the benefits of PCI in STEMI latecomers with different MaR.Results:The results were divided into three parts:1. Benefit of elective PCI for STEMI15,799STEMI patients were enrolled with two-year follow-up. Of these patients,5,417underwent PCI2-28days and10,382received routine medical therapy alone.The two-year cumulative MACE rate was significant lower in PCI group comparedwith conservative group (10.1%vs.20.4%; covariate-adjusted HR,0.417;95%CI,0.375-0.464; P<0.001). Adjusted HR in propensity-score matched patients was0.494(95%CI,0.442-0.551; P<0.001). Also, PCI was negatively associated with theoccurrence of MACE (adjusted OR,0.451;95%CI,0.392-0.538) in the mixed-effectmodel. In conclusion, elective PCI could significantly reduce the incidence oftwo-year MACE for stable STEMI patients not receiving early reperfusion treatment.2. Influence of timing of elective PCI on prognosis of STEMI5,417STEMI patients met the aforementioned criteria. Of these,55.9%,35.4%and8.7%received elective PCI on Day2-7, Day8-14and Day15-28from onset,respectively. At baseline, age and hospital level was associated with the selection oftiming. There was no significant difference in one-year cumulative MACE ratesamong the three groups (7.1%,5.8%and6.3%; log-rank test P=0.272), and thetiming itself was not an independent predictor of MACE (P>0.05). In conclusion, thetiming selection of elective PCI varies in clinical practice but there was no significantassociation between the timing of elective PCI and one-year MACE.3. Influence of myocardial area at risk on prognosis of early latecomers withSTEMIWe constructed a prospective cohort involving436patients presenting12to72hours after STEMI onset and who met an inclusion criteria. Of218underwent PCIand218received the optimal medical therapy (OMT) alone. Individual myocardial area at risk (MaR) was quantified by the combined Aldrich ST and Selvester QRSscore. The primary endpoint was a composite of cardiovascular death, reinfarction orrevascularization within two years. The2-year cumulative primary endpoint rate wasrespectively9.2%in PCI group and5.3%in OMT group when MaR<35%(adjustedHR for PCI vs. OMT,1.855;95%CI,0.617-5.575; P=0.271), and was12.8%in PCIgroup and23.1%in OMT group when MaR≥35%(adjusted HR for PCI vs. OMT,0.448;95%CI,0.228-0.884; P=0.021). In conclusion, the benefit of PCI for theSTEMI latecomers was associated with the MaR.Conclusion:We have first investigated whether the stable post-MI patients with elective PCIcompared with the conservative therapy could get more survival benefit and free ofMACEs in the real world. We found that elective PCI could significantly reduce theincidence of two-year MACE including cardiovascular death, reinfarction and repeatrevascularization compared with medical therapy alone for these patients. Then wehave investigated whether the timing of elective PCI could impact on the prognosis ofstable post-MI patients without early reperfusion therapy and whether there is aoptimal timing for performing elective PCI in these patients. We found that the timingselection of elective PCI varies in clinical practice but there was no significantassociation between the timing of PCI and one-year MACE incidence. Finally, wehave investigated whether the MaR could impact on the selection of reperfusiontherapy (PCI or medical therapy alone) for stable post-MI latecomers. We found thatthe benefit of PCI for the STEMI latecomers was associated with the MaR. PCI,compared with OMT, could significantly reduce the two-year primary outcomes inpatients with MaR≥35%, but not in ones with MaR<35%. The present study answeredthe question the outcomes of stable STEMI patients with or without elective PCI inthe real-world and related risk factors. It would have important implications for futuredevelopment of guidelines and the design of clinical trials.