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Lethal reperfusion injury is a paradoxical type of myocardial injury caused by the restoration of coronary blood flow after an ischemic episode. This review focuses on the mechanisms of the injury, on attempts to protect the heart against it, and on promising new approaches to cardioprotection during percutaneous coronary intervention. This review focuses on the mechanisms of myocardial injury, on attempts to protect the heart against it, and on promising new approaches to cardioprotection during percutaneous coronary intervention. Coronary heart disease is the leading cause of death worldwide, and 3.8 million men and 3.4 million women die of the disease each year. After an acute myocardial infarction, early and successful myocardial reperfusion with the use of thrombolytic therapy or primary percutaneous coronary intervention (PCI) is the most effective strategy for reducing the size of a myocardial infarct and improving the clinical outcome. The process of restoring blood flow to the ischemic myocardium, however, can induce injury. This phenomenon, termed myocardial reperfusion injury, can paradoxically reduce the beneficial effects of myocardial reperfusion. The potentially detrimental aspect of myocardial reperfusion . . .

Microvascular obstruction (MO) or no-reflow phenomenon is an established complication of coronary reperfusion therapy for acute myocardial infarction. It is increasingly recognized as a poor prognostic indicator and marker of subsequent adverse LV remodeling. Although MO can be assessed using various imaging modalities including electrocardiography, myocardial contrast echocardiography, nuclear scintigraphy, and coronary angiography, evaluation by cardiovascular magnetic resonance (CMR) is particularly useful in enhancing its detection, diagnosis, and quantification, as well as following its subsequent effects on infarct evolution and healing. MO assessment has become a routine component of the CMR evaluation of acute myocardial infarction and will increasingly play a role in clinical trials of adjunctive reperfusion agents and strategies. This review will summarize the pathophysiology of MO, current CMR approaches to diagnosis, clinical implications, and future directions needed for improving our understanding of this common clinical problem.

Keypoints:It is unclear what role, if any, intracoronary thrombolysis plays in the management of ST-segment elevation myocardial infarction (STEMI) with primary percutaneous coronary intervention (PPCI).In this meta-analysis intracoronary thrombolysis-facilitated PPCI for STEMI was associated with improved outcomes compared to standard PPCI.A randomized controlled trial would be necessary to settle the question of whether intracoronary thrombolysis is a useful adjunct to PPCI and whether it is most effective before, during, or after PPCI.

Background Large body of evidences accumulated in clinical and epidemiological studies indicate that hearts of diabetic subjects are more sensitive to ischemia reperfusion injury (IRI), which results in a higher rate of mortality at post-operation than that of non-diabetes. However, experimental results are equivocal and point to either increased or decreased susceptibility of the diabetic hearts to IRI, especially at the early stage of the disease. The present study was designed to test the hypothesis that the duration/severity of the indexed ischemia is a major determinant of the vulnerability to myocardial IRI at early stage of diabetes. Methods Four weeks streptozotocin (STZ)-induced diabetic (D) and non-diabetic (C) Sprague–Dawley rats were randomly assigned to receive 30 or 45 min of left anterior descending artery ligation followed by 2 or 3 hours of reperfusion, respectively. Cardiac function was recorded by using Pressure-Volume (PV) conduction system. Myocardial infarct size was determined with triphenyltetrazolium chloride staining. Plasma Creatine kinase-MB (CK-MB), Lactate dehydrogenase (LDH) release, myocardial nitric oxide(NO) content and nitrotyrosine formation, 15-F 2t -Isoprostane and plasma superoxide dismutase (SOD) were measured with colorimetric assays. Cardiomyocyte apoptosis was assessed by TUNEL staining. Myocardial TNFα, Caspase-3, STAT3, Akt, and GSK-3β were determined by Western blotting. Results Prolongation of ischemia but not reperfusion from 30 min to 45 min significantly increased infarct size in D compared to C rats ( P  < 0.05), accompanied with significantly increased plasma CK-MB ( P  < 0.05). Prolongation of the duration of either ischemia or reperfusion significantly increased plasma LDH release and myocardial 15-F 2t -Isoprostane and reduced plasma SOD activity, with concomitant reduction of myocardial NO and increase of nitrotyrosine formation in D relative to C ( P  < 0.05). Prolongation of ischemia and reperfusion significantly reduced left ventricular ejection fraction and increased the peak rate of pressure, accompanied with increased end systolic pressure in D relative to C rats ( P  < 0.05) but reduced phosphorylations of myocardial STAT3 at site Ser727 and Akt at site Ser473 as well as GSK-3β at Ser 9 ( P  < 0.05). Conclusions Diabetic hearts, even at early stage of the disease are more sensitive to IRI, and this increased severity of post-ischemic myocardial injury depends more on the duration of ischemia than that of reperfusion.

The size of the myocardial infarction remains an important therapeutic target, because heart attack size correlates with mortality and heart failure. In this era, myocardial infarct size is reduced primarily by timely reperfusion of the infarct related coronary artery. Whereas numerous pre-clinical studies have shown that certain pharmacologic agents and therapeutic maneuvers reduce myocardial infarction size greater than reperfusion alone, very few of these therapies have translated to successful clinical trials or standard clinical use. In this review we discuss both the recent successes as well as recent disappointments, and describe some of the newer potential therapies from the preclinical literature that have not yet been tested in clinical trials.

Background Impaired glucose metabolism is an established risk factor for coronary artery disease. Previous studies revealed that glycemic variability (GV) is also important for glucose metabolism in patients with acute coronary syndrome (ACS). We explored the association between GV and prognosis in patients with ACS. Methods A total of 417 patients with ACS who received reperfusion wore a continuous glucose monitoring system (CGMS) in a stable phase after admission and were monitored for at least 24 consecutive h. The mean amplitude of glycemic excursion (MAGE) was calculated as a marker of GV. We divided into two groups based on the highest tertile levels of MAGE (MAGE = 52 mg/dl). The groups were followed up for a median of 39 months [IQR 24–50 months]. The primary endpoint was the incidence of major adverse cardiovascular and cerebrovascular events (MACCE). Result During follow-up, 66 patients experienced MACCE (5 patients had cardiovascular death, 14 had recurrence of ACS, 27 had angina requiring revascularization, 8 had acute decompensated heart failure, and 16 had a stroke). MACCE was more frequently observed in the high MAGE group (23.5% vs. 11.6%, p  = 0.002). In multivariate analysis, high MAGE was an independent predictive factor of poor prognosis for MACCE (odds ratio, 1.84; 95% confidence interval, 1.01–3.36; p  = 0.045). Conclusion Glycemic variability determined with a CGMS is a predictor of prognosis in patients with ACS without severe DM. Trial registration UMIN 000010620. Registered April 1st 2012

Background To investigate the influence of cardiovascular magnetic resonance (CMR) timing after reperfusion on CMR-derived parameters of ischemia/reperfusion (I/R) injury in patients with ST-segment elevation myocardial infarction (STEMI). Methods The study included 163 reperfused STEMI patients undergoing CMR during the index hospitalization. Patients were divided according to the time between revascularization and CMR (T revasc-CMR : Tertile-1 ≤ 43; 43 < Tertile-2 ≤ 93; Tertile-3 > 93 h). T2-mapping derived area-at-risk (AAR) and intramyocardial-hemorrhage (IMH), and late gadolinium enhancement (LGE)-derived infarct size (IS) and microvascular obstruction (MVO) were quantified. T1-mapping was performed before and > 15 min after Gd-based contrast-agent administration yielding extracellular volume (ECV) of infarct. Results Main factors influencing I/R injury were homogenously balanced across T revasc-CMR tertiles. T2 values of infarct and remote regions increased with increasing T revasc-CMR tertiles (infarct: 60.0 ± 4.9 vs 63.5 ± 5.6 vs 64.8 ± 7.5 ms; P  < 0.001; remote: 44.3 ± 2.8 vs 46.1 ± 2.8 vs ± 46.1 ± 3.0; P  = 0.001). However, T2 value of infarct largely and significantly exceeded that of remote myocardium in each tertile yielding comparable T2-mapping-derived AAR extent throughout T revasc-CMR tertiles (17 ± 9% vs 19 ± 9% vs 18 ± 8% of LV, respectively, P  = 0.385). Similarly, T2-mapping-based IMH detection and quantification were independent of T revasc-CMR . LGE-derived IS and MVO were not influenced by T revasc-CMR (IS: 12 ± 9% vs 12 ± 9% vs 14 ± 9% of LV, respectively, P  = 0.646). In 68 patients without MVO, T1-mapping based ECV of infarct region was comparable across T revasc-CMR tertiles ( P  = 0.470). Conclusion In STEMI patients, T2 values of infarct and remote myocardium increase with increasing CMR time after revascularization. However, these changes do not give rise to substantial variation of T2-mapping-derived AAR size nor of other CMR-based parameters of I/R. Trial registration ISRCTN03522116 . Registered 30.4.2018 (retrospectively registered).

BackgroundIn patients with acute myocardial infarction, restoration of coronary flow by primary coronary intervention (PCI) can lead to profound ischaemia-reperfusion injury with detrimental effects on myocardial salvage. Non-invasive assessment of interstitial myocardial haemorrhage by T2* cardiac MRI (T2*-CMR) provides a novel and specific biomarker of severe reperfusion injury which may be of prognostic value.ObjectiveTo characterise the determinants of acute ischaemia-reperfusion injury following ST elevation myocardial infarction (STEMI) using CMR.Methods and resultsFifty patients with acute STEMI who had been successfully treated by PCI were studied. T2*-CMR was used to identify the presence of reperfusion haemorrhage and contrast enhancement was used to measure microvascular obstruction (MVO) and infarct size. Haemorrhagic ischaemia-reperfusion injury was present in 29 patients (58%) following PCI and occurred despite rapid revascularisation (mean 4.2±3.3 h). Haemorrhage was only present when the infarct involved at least 80% (mean±SD 91±5.3%) of the left ventricular wall thickness. There was a strong association between the extent of MVO and reperfusion haemorrhage (r2=0.87, p<0.001). Transmural infarcts (n=43) showed significantly impaired systolic wall thickening at the infarct mid point when reperfusion haemorrhage was present (21.5±16.7% vs 3.7±12.9%), p<0.0001) compared with non-haemorrhagic infarcts.ConclusionsSevere reperfusion injury may occur when there is near-transmural myocardial necrosis despite early and successful revascularisation. Reperfusion haemorrhage is closely associated with the development of MVO. These findings indicate that, once advanced necrosis has developed, the potential for severe myocardial reperfusion injury is significantly enhanced.

Reperfusion therapy is the most important method for treating acute myocardial infarction. However, myocardial ischemia reperfusion injury (MIRI) can offset the benefit of reperfusion therapy and worsen the outcome. In both ischemia and reperfusion, autophagy remains problematic. Activating molecule in Beclin1-regulated autophagy (Ambra1) is an important protein in autophagy regulation, and its function in MIRI remains unclear. Thus, we used H9C2 cells to investigate the function of Ambra1 in MIRI and the underlying mechanisms involved. Hypoxia and reoxygenation of H9C2 cells were used to mimic MIRI in vitro. During hypoxia, autophagy flux was blocked, then recovered in reoxygenation. Ambra1 overexpression increased autophagy in the H9C2 cells, as the LC3B II/I ratio increased, and alleviated cellular necrosis and apoptosis during hypoxia and reoxygenation. This effect was counteracted by an autophagy inhibitor. Knocking down Ambra1 can block autophagy which P62 sediment/supernatant ratio increased while the ratio of LC3B II/I decreased, and worsen outcomes. Ambra1 enhances autophagy in H9C2 cells by improving the stability and activity of the ULK1 complex. Reactive oxygen species (ROS) are an important cause of MIRI. ROS were reduced when Ambra1 was overexpressed and increased when Ambra1 was knocked down, indicating that Ambra1 can protect against hypoxia and reoxygenation injury in H9C2 cells by promoting autophagy and reducing ROS.

ObjectiveST-elevation myocardial infarction (STEMI) is frequently associated with reciprocal ST-segment depression in contralateral ECG leads. However, the relationship of the resolution of ST-segment depression (STD-R) with myocardial damage is unknown and the potential prognostic value incompletely understood. We sought to evaluate the association between STD-R and markers of myocardial injury as well as to determine the prognostic impact of STD-R in patients with acute reperfused STEMI.MethodsWe enrolled 611 patients with STEMI in this multicentre cardiac magnetic resonance (CMR) study. STD-R, defined as either worsened (<0%), incomplete (0–50%) or complete (≥50%), was determined 90 min after primary percutaneous coronary intervention (PCI). Patients underwent CMR in median 3 (2–4) days after infarction. Major adverse cardiac events (MACE) were defined as a composite of death, reinfarction and new congestive heart failure within 12 months after enrolment.ResultsPatients with worsened or incomplete STD-R (n=148 (24.2%)) had a significantly larger area at risk (42 (31–50) vs 37 (29–52) vs 34 (24–46) %LV, p=0.001), larger infarct size (20 (13–30) vs 17(10–26) vs 16 (8–24) %LV, p=0.003), larger extent of microvascular obstruction (0.6(0–3.4) vs 0.4 (0–2.4) vs 0.0 (0–1.4) %LV, p=0.003), and a lower LVEF (46 (39–54) vs 48 (40–56) vs 52 (45–58) %, p<0.001). MACE rate (n=37 (6%)) was significantly higher in patients with worsened (n=10 (19%)) or incomplete STD-R (n=7 (7%)) than in patients with complete STD-R (n=20 (4%), p<0.001). In multivariate Cox regression analysis, categorised STD-R emerged as an independent predictor of MACE at 12 months after adjusting for clinical variables (p=0.007).ConclusionsPatients with acute STEMI and worsened or incomplete STD-R after PCI show a more pronounced myocardial as well as microvascular damage as detected by CMR with subsequent independent prognostic information on MACE over a 12-month follow-up period.