Remote ischemic post-conditioning of the lower limb during primary percutaneous coronary intervention safely reduces enzymatic infarct size in anterior myocardial infarction: a randomized controlled trial

Effect of Remote Ischemic Preconditioning on Perioperative Cardiac Events in Patients Undergoing Elective Percutaneous Coronary Intervention: A Meta-Analysis of 16 Randomized Trials

Background

The main objective of this meta-analysis was to investigate whether remote ischemic preconditioning (RIPC) reduces cardiac and renal events in patients undergoing elective cardiovascular interventions.

Methods and Results

We systematically searched articles published from 2006 to 2016 in PubMed, EMBASE, Web of Science, Cochrane Library, and Google Scholar. Odds ratios (ORs) with 95% confidence intervals (CIs) were used as the effect index for dichotomous variables. The standardized mean differences (SMDs) with 95% CIs were calculated as the pooled continuous effect. Sixteen RCTs of 2435 patients undergoing elective PCI were selected. Compared with control group, RIPC could significantly reduce the incidence of perioperative myocardial infarction (OR = 0.64; 95% CI: 0.48–0.86; P = 0.003) and acute kidney injury (OR = 0.56; 95% CI: 0.322–0.99; P = 0.049). Metaregression analysis showed that the reduction of PMI by RIPC was enhanced for CAD patients with multivessel disease (coef.: −0.05 [−0.09; −0.01], P = 0.022). There were no differences in the changes of cTnI (P = 0.934) and CRP (P = 0.075) in two groups.

Conclusion

Our meta-analysis of RCTs demonstrated that RIPC can provide cardiac and renal protection for patients undergoing elective PCI, while no beneficial effect on reducing the levels of cTnI and CRP after PCI was reported.

Remote tissue conditioning - An emerging approach for inducing body-wide protection against diseases of ageing

We have long accepted that exercise is 'good for us'; that - put more rigorously - moderate exercise is associated with not just aerobic fitness but also reduced morbidity and reduced mortality from cardiovascular disease and even malignancies. Caloric restriction (moderate hunger) and our exposure to dietary phytochemicals are also emerging as stresses which are 'good for us' in the same sense. This review focuses on an important extension of this concept: that stress localized within the body (e.g. in a limb) can induce resilience in tissues throughout the body. We describe evidence for the efficacy of two 'remote' protective interventions - remote ischemic conditioning and remote photobiomodulation - and discuss the mechanisms underlying their protective actions. While the biological phenomenon of remote tissue conditioning is only partially understood, it holds promise for protecting critical-to-life tissues while mitigating risks and practical barriers to direct conditioning of these tissues.

Dynamic Edematous Response of the Human Heart to Myocardial Infarction: Implications for Assessing Myocardial Area at Risk and Salvage

Supplemental Digital Content is available in the text.

Background:

Clinical protocols aimed to characterize the post–myocardial infarction (MI) heart by cardiac magnetic resonance (CMR) need to be standardized to take account of dynamic biological phenomena evolving early after the index ischemic event. Here, we evaluated the time course of edema reaction in patients with ST-segment–elevation MI by CMR and assessed its implications for myocardium-at-risk (MaR) quantification both in patients and in a large-animal model.

Methods:

A total of 16 patients with anterior ST-segment–elevation MI successfully treated by primary angioplasty and 16 matched controls were prospectively recruited. In total, 94 clinical CMR examinations were performed: patients with ST-segment–elevation MI were serially scanned (within the first 3 hours after reperfusion and at 1, 4, 7, and 40 days), and controls were scanned only once. T2 relaxation time in the myocardium (T2 mapping) and the extent of edema on T2-weighted short-tau triple inversion-recovery (ie, CMR-MaR) were evaluated at all time points. In the experimental study, 20 pigs underwent 40-minute ischemia/reperfusion followed by serial CMR examinations at 120 minutes and 1, 4, and 7 days after reperfusion. Reference MaR was assessed by contrast-multidetector computed tomography during the index coronary occlusion. Generalized linear mixed models were used to take account of repeated measurements.

Results:

In humans, T2 relaxation time in the ischemic myocardium declines significantly from early after reperfusion to 24 hours, and then increases up to day 4, reaching a plateau from which it decreases from day 7. Consequently, edema extent measured by T2-weighted short-tau triple inversion-recovery (CMR-MaR) varied with the timing of the CMR examination. These findings were confirmed in the experimental model by showing that only CMR-MaR values for day 4 and day 7 postreperfusion, coinciding with the deferred edema wave, were similar to values measured by reference contrast-multidetector computed tomography.

Conclusions:

Post-MI edema in patients follows a bimodal pattern that affects CMR estimates of MaR. Dynamic changes in post–ST-segment–elevation MI edema highlight the need for standardization of CMR timing to retrospectively delineate MaR and quantify myocardial salvage. According to the present clinical and experimental data, a time window between days 4 and 7 post-MI seems a good compromise solution for standardization. Further studies are needed to study the effect of other factors on these variables.

Remote Ischemic Conditioning for Patients With STEMI

ST-segment elevation myocardial infarction (STEMI) remains a leading cause of death and morbidity, despite declining incidence and improved short-term outcome in many countries. Although mortality declines in developed countries with easy and fast access to optimized treatment, development of heart failure often remains a challenge in survivors and still approaches 10% at 1 year. Rapid admission and acute interventional treatment combined with modern antithrombotic pharmacologic therapy frequently establish complete reperfusion and acutely stabilize the patient, but the reperfusion itself adds further to the damage in the myocardium compromising the long-term outcome. Reperfusion injury is believed to be a significant-if not the dominant-contributor to the net injury resulting from STEMI and has become a major focus of research in recent years. Despite a plethora of pharmacological and mechanical interventions showing consistent reduction of reperfusion injury in experimental models, translation into a clinical setting has been challenging. In patients, attempts to modify reperfusion injury by pharmacological strategies have largely been unsuccessful, and focus is increasingly directed toward mechanical modalities. Remote ischemic conditioning of the heart is achieved by repeated brief interruption of the blood supply to a distant part of the body, most frequently the arm. At present, remote ischemic conditioning is the most promising adjuvant therapy to reduce reperfusion injury in patients with STEMI. In this review, we discuss the results of clinical trials investigating the effect of remote ischemic conditioning in patients admitted with STEMI and potential reasons for its apparent superiority to current pharmacologic adjuvant therapies.

The application of remote ischemic conditioning in cardiac surgery

Perioperative myocardial ischemia and infarction are the leading causes of morbidity and mortality following anesthesia and surgery. The discovery of endogenous cardioprotective mechanisms has led to testing of new methods to protect the human heart. These approaches have included ischemic pre-conditioning, per-conditioning, post-conditioning, and remote conditioning of the myocardium. Pre-conditioning and per-conditioning include brief and repetitive periods of sub-lethal ischemia before and during prolonged ischemia, respectively; and post-conditioning is applied at the onset of reperfusion. Remote ischemic conditioning involves transient, repetitive, non-lethal ischemia and reperfusion in one organ or tissue (remote from the heart) that renders myocardium more resistant to lethal ischemia/reperfusion injury. In healthy, young hearts, many conditioning maneuvers can significantly increase the resistance of the heart against ischemia/reperfusion injury. The large multicenter clinical trials with ischemic remote conditioning have not been proven successful in cardiac surgery thus far. The lack of clinical success is due to underlying risk factors that interfere with remote ischemic conditioning and the use of cardioprotective agents that have activated the endogenous cardioprotective mechanisms prior to remote ischemic conditioning. Future preclinical research using remote ischemic conditioning will need to be conducted using comorbid models.

Mechanical strategies to enhance myocardial salvage during primary percutaneous coronary intervention in patients with STEMI

Primary percutaneous coronary intervention (PPCI) has become the mainstay of reperfusion therapy in patients with ST-segment elevation myocardial infarction (STEMI). Despite timely reperfusion by PPCI and restoration of epicardial blood flow in up to 95% of patients, tissue reperfusion remains suboptimal in a sizeable proportion of patients with STEMI. Over the years mechanical and pharmacological strategies to enhance myocardial salvage during PPCI have been developed and used in patients with STEMI. The most common mechanical strategies used in the setting of PPCI include: coronary stenting, direct stenting, mesh-covered stents, self-expanding stents, deferred stenting, thrombectomy, distal protection devices, intra-aortic balloon pumping, left ventricular assist devices and ischaemic conditioning. These strategies are thought to enhance myocardial salvage via improving acute procedural success, attenuation of distal embolisation, microvascular obstruction and reperfusion injury, and providing haemodynamic support. Coronary (direct) stenting is almost the default approach of reperfusion during PPCI procedures. Evidence on the use of mesh-covered stents, self-expanding stents, deferred stenting or left ventricular assist devices is scant and their use in the setting of PPCI remains limited. Mechanical thrombectomy, distal protection devices or routine intra-aortic balloon counterpulsation seem to offer no clinical benefit when used in the setting of PPCI. Although manual aspiration may improve indices of tissue reperfusion, recent research showed no clinical benefit of routine use of this strategy in patients with STEMI undergoing PPCI. Ischaemic conditioning, although promising, remains at an investigational stage and needs further research.

Quantifying the area-at-risk of myocardial infarction in-vivo using arterial spin labeling cardiac magnetic resonance

T₂-weighted cardiovascular magnetic resonance (T2-CMR) of myocardial edema can quantify the area-at-risk (AAR) following acute myocardial infarction (AMI), and has been used to assess myocardial salvage by new cardioprotective therapies. However, some of these therapies may reduce edema, leading to an underestimation of the AAR by T2-CMR. Here, we investigated arterial spin labeling (ASL) perfusion CMR as a novel approach to quantify the AAR following AMI. Adult B6sv129-mice were subjected to in vivo left coronary artery ligation for 30 minutes followed by 72 hours reperfusion. T₂-mapping was used to quantify the edema-based AAR (% of left ventricle) following ischemic preconditioning (IPC) or cyclosporin-A (CsA) treatment. In control animals, the AAR by T2-mapping corresponded to that delineated by histology. As expected, both IPC and CsA reduced MI size. However, IPC, but not CsA, also reduced myocardial edema leading to an underestimation of the AAR by T₂-mapping. In contrast, regions of reduced myocardial perfusion delineated by cardiac ASL were able to delineate the AAR when compared to both T2-mapping and histology in control animals, and were not affected by either IPC or CsA. Therefore, ASL perfusion CMR may be an alternative method for quantifying the AAR following AMI, which unlike T2-mapping, is not affected by IPC.

The Coronary Circulation as a Target of Cardioprotection

The atherosclerotic coronary vasculature is not only the culprit but also a victim of myocardial ischemia/reperfusion injury. Manifestations of such injury are increased vascular permeability and edema, endothelial dysfunction and impaired vasomotion, microembolization of atherothrombotic debris, stasis with intravascular cell aggregates, and finally, in its most severe form, capillary destruction with hemorrhage. In animal experiments, local and remote ischemic pre- and postconditioning not only reduce infarct size but also these manifestations of coronary vascular injury, as do drugs which recruit signal transduction steps of conditioning. Clinically, no-reflow is frequently seen after interventional reperfusion, and it carries an adverse prognosis. The translation of cardioprotective interventions to clinical practice has been difficult to date. Only 4 drugs (brain natriuretic peptide, exenatide, metoprolol, and esmolol) stand unchallenged to date in reducing infarct size in patients with reperfused acute myocardial infarction; unfortunately, for these drugs, no information on their impact on the ischemic/reperfused coronary circulation is available.

Impact of Remote Ischemic Postconditioning during Primary Percutaneous Coronary Intervention on Left Ventricular Remodeling after Anterior Wall ST-Segment Elevation Myocardial Infarction: A Single-Center Experience

The role of remote ischemic postconditioning (RIPostC) in improving left ventricular (LV) remodeling after primary percutaneous coronary intervention (PCI) is not well established. To determine the efficacy and safety of RIPostC in improving LV remodeling and cardiovascular outcomes after primary PCI for anterior ST-elevation myocardial infarction (STEMI). Seventy-one patients with anterior STEMI were randomized to primary PCI with RIPostC protocol ( n  = 36) versus conventional primary PCI ( n  = 35). Primary outcomes included LV remodeling and LV ejection fraction (LVEF) at 6 month follow-up using transthoracic echocardiography. Secondary outcomes included infarct size, ST-segment resolution (STR) ≥70%, Thrombolysis in Myocardial Infarction (TIMI) flow grade, and myocardial blush grade (MBG). Major adverse cardiac events (MACEs) were also assessed at 6 months. Safety outcome included incidence of acute kidney injury (AKI) postprimary PCI. Sixty patients completed the study. At 6 months, there was no significant decrease in the incidence of LV remodeling with RIPostC group ( p  = 0.42). Similarly, RIPostC failed to show significant improvement in LVEF. However, STR ≥ 70% after primary PCI was achieved more in the RIPostC group ( p  = 0.04), with a trend toward less AKI in the RIPostC group ( p  = 0.08). All other secondary end points, including MACEs at 6 months, were similar in both groups. RIPostC might be associated with better STR after reperfusion as well as less incidence of AKI in patients undergoing primary PCI for anterior wall STEMI, indicating potential benefit in those patients. Whether this role can be translated to better outcomes after primary PCI warrants further investigation.

Remote Ischemic Conditioning and Renal Protection

Over the course of the last 2 decades, the concept of remote ischemic conditioning (RIC) has attracted considerable research interest, because RIC, in most of its embodiments offers an inexpensive way of protecting tissues against ischemic damage inflicted by a number of medical conditions or procedures. Acute kidney injury (AKI) is a common side effect in the context of various medical procedures, and RIC has been suggested as a means of reducing its incidence. Outcomes regarding kidney function have been reported in numerous studies that evaluated the effects of RIC in a variety of settings (eg, cardiac surgery, interventions requiring intravenous administration of contrast media). Although several individual studies have implied a beneficial effect of RIC in preserving kidney function, 3 recently published randomized controlled trials evaluating more than 1000 patients each (Effect of Remote Ischemic Preconditioning in the Cardiac Surgery, Remote Ischaemic Preconditioning for Heart Surgery, and ERICCA) were negative. However, AKI or any other index of renal function was not a stand-alone primary end point in any of these trials. On the other hand, a range of meta-analyses (each including thousands of participants) have reported mixed results, with the most recent among them showing benefit from RIC, pinpointing at the same time a number of shortcomings in published studies, adversely affecting the quality of available data. The present review provides a critical appraisal of the current state of this field of research. It is the opinion of the authors of this review that there is a clear need for a common clinical trial framework for ischemic conditioning studies. If the current babel of definitions, procedures, outcomes, and goals persists, it is most likely that soon ischemic conditioning will be "yesterday's news" with no definitive conclusions having been reached in terms of its real clinical utility.

Is there a role for ischaemic conditioning in cardiac surgery?

Coronary artery disease (CAD) is a major cause of morbidity and mortality worldwide. Coronary artery bypass graft (CABG) surgery is the revascularisation strategy of choice in patients with diabetes mellitus and complex CAD. Owing to a number of factors, including the ageing population, the increased complexity of CAD being treated, concomitant valve and aortic surgery, and multiple comorbidities, higher-risk patients are being operated on, the result of which is an increased risk of sustaining perioperative myocardial injury (PMI) and poorer clinical outcomes. As such, new treatment strategies are required to protect the heart against PMI and improve clinical outcomes following cardiac surgery. In this regard, the heart can be endogenously protected from PMI by subjecting the myocardium to one or more brief cycles of ischaemia and reperfusion, a strategy called "ischaemic conditioning". However, this requires an intervention applied directly to the heart, which may be challenging to apply in the clinical setting. In this regard, the strategy of remote ischaemic conditioning (RIC) may be more attractive, as it allows the endogenous cardioprotective strategy to be applied away from the heart to the arm or leg by simply inflating and deflating a cuff on the upper arm or thigh to induce one or more brief cycles of ischaemia and reperfusion (termed "limb RIC"). Although a number of small clinical studies have demonstrated less PMI with limb RIC following cardiac surgery, three recently published large multicentre randomised clinical trials found no beneficial effects on short-term or long-term clinical outcomes, questioning the role of limb RIC in the setting of cardiac surgery. In this article, we review ischaemic conditioning as a therapeutic strategy for endogenous cardioprotection in patients undergoing cardiac surgery and discuss the potential reasons for the failure of limb RIC to improve clinical outcomes in this setting. Crucially, limb RIC still has the therapeutic potential to protect the heart in other clinical settings, such as acute myocardial infarction, and it may also protect other organs against acute ischaemia/reperfusion injury (such as the brain, kidney, and liver).

In vivo MRI and ex vivo histological assessment of the cardioprotection induced by ischemic preconditioning, postconditioning and remote conditioning in a closed-chest porcine model of reperfused acute myocardial infarction: importance of microvasculature

BACKGROUND

Cardioprotective value of ischemic post- (IPostC), remote (RIC) conditioning in acute myocardial infarction (AMI) is unclear in clinical trials. To evaluate cardioprotection, most translational animal studies and clinical trials utilize necrotic tissue referred to the area at risk (AAR) by magnetic resonance imaging (MRI). However, determination of AAR by MRI' may not be accurate, since MRI-indices of microvascular damage, i.e., myocardial edema and microvascular obstruction (MVO), may be affected by cardioprotection independently from myocardial necrosis. Therefore, we assessed the effect of IPostC, RIC conditioning and ischemic preconditioning (IPreC; positive control) on myocardial necrosis, edema and MVO in a clinically relevant, closed-chest pig model of AMI.

METHODS AND RESULTS

Acute myocardial infarction was induced by a 90-min balloon occlusion of the left anterior descending coronary artery (LAD) in domestic juvenile female pigs. IPostC (6 × 30 s ischemia/reperfusion after 90-min occlusion) and RIC (4 × 5 min hind limb ischemia/reperfusion during 90-min LAD occlusion) did not reduce myocardial necrosis as assessed by late gadolinium enhancement 3 days after reperfusion and by ex vivo triphenyltetrazolium chloride staining 3 h after reperfusion, however, the positive control, IPreC (3 × 5 min ischemia/reperfusion before 90-min LAD occlusion) did. IPostC and RIC attenuated myocardial edema as measured by cardiac T2-weighted MRI 3 days after reperfusion, however, AAR measured by Evans blue staining was not different among groups, which confirms that myocardial edema is not a measure of AAR, IPostC and IPreC but not RIC decreased MVO.

CONCLUSION

We conclude that IPostC and RIC interventions may protect the coronary microvasculature even without reducing myocardial necrosis.

Cardioprotection: Where to from here?

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.

Meta-Analysis of Randomized Trials on Remote Ischemic Conditioning During Primary Percutaneous Coronary Intervention in Patients With ST-Segment Elevation Myocardial Infarction

Ischemia/reperfusion injury adversely affects the final infarct size (IS) after primary percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI). Few studies have evaluated the role of remote ischemic conditioning (RIC) in reducing ischemia/reperfusion injury. However, the results of these studies were not consistent, and an overview of overall effectiveness of this technique in patients with STEMI is lacking. We conducted this meta-analysis to evaluate the available evidence in literature regarding the application of RIC in patients with STEMI who underwent primary PCI. The authors included randomized trials that studied RIC in patients with STEMI who underwent primary PCI versus no conditioning (standard of care). Final analysis included 8 trials with a total of 1,083 patients. Compared with standard of care alone, RIC was associated with reduced IS assessed by biomarker release (standardized mean difference = -0.23, 95% confidence interval [CI] -0.37 to -0.09; p = 0.001), better rates of ST-segment resolution (54% vs 30%; relative risk [RR] 1.78; 95% CI 1.35 to 2.34; p <0.001), reduced major adverse cardiac and cerebrovascular events (11% vs 20%; RR 0.57; 95% CI 0.39 to 0.83; p = 0.003), and nonsignificant reduction in IS assessed by cardiac imaging (standardized mean difference = -0.15; 95% CI -1.03 to -0.14; p = 0.36). There was no difference in postprocedural Thrombolysis In Myocardial Infarction-III flow between RIC and standard of care groups (86% vs 87%; RR 0.99; 95% CI 0.94 to 1.05; p = 0.81). In conclusion, remote ischemic conditioning may improve cardiovascular outcomes in patients with STEMI who underwent primary PCI evidenced by reduced biomarkers release, major adverse cardiac and cerebrovascular events, and better ST-segment resolution.

Defining left ventricular remodeling following acute ST-segment elevation myocardial infarction using cardiovascular magnetic resonance

BACKGROUND

The assessment of post-myocardial infarction (MI) left ventricular (LV) remodeling by cardiovascular magnetic resonance (CMR) currently uses criteria defined by echocardiography. Our aim was to provide CMR criteria for assessing LV remodeling following acute MI.

METHODS

Firstly, 40 reperfused ST-segment elevation myocardial infarction (STEMI) patients with paired acute (4 ± 2 days) and follow-up (5 ± 2 months) CMR scans were analyzed by 2 independent reviewers and the minimal detectable changes (MDCs) for percentage change in LV end-diastolic volume (%ΔLVEDV), LV end-systolic volume (%ΔLVESV), and LV ejection fraction (%ΔLVEF) between the acute and follow-up scans were determined. Secondly, in 146 reperfused STEMI patients, receiver operator characteristic curve analyses for predicting LVEF <50% at follow-up (as a surrogate for clinical poor clinical outcome) were undertaken to obtain cut-off values for %ΔLVEDV and %ΔLVESV.

RESULTS

The MDCs for %ΔLVEDV, %ΔLVESV, and %ΔLVEF were similar at 12%, 12%, 13%, respectively. The cut-off values for predicting LVEF < 50% at follow-up were 11% for %ΔLVEDV on receiver operating characteristic curve analysis (area under the curve (AUC) 0.75, 95% CI 0.6 to 0.83, sensitivity 72% specificity 70%), and 5% for %ΔLVESV (AUC 0.83, 95% CI 0.77 to 0.90, sensitivity and specificity 78%). Using cut-off MDC values (higher than the clinically important cut-off values) of 12% for both %ΔLVEDV and %ΔLVESV, 4 main patterns of LV remodeling were identified in our cohort: reverse LV remodeling (LVEF predominantly improved); no LV remodeling (LVEF predominantly unchanged); adverse LV remodeling with compensation (LVEF predominantly improved); and adverse LV remodeling (LVEF unchanged or worsened).

CONCLUSIONS

The MDCs for %ΔLVEDV and %ΔLVESV between the acute and follow-up CMR scans of 12% each may be used to define adverse or reverse LV remodeling post-STEMI. The MDC for %ΔLVEF of 13%, relative to baseline, provides the minimal effect size required for investigating treatments aimed at improving LVEF following acute STEMI.

Meta-analysis of remote ischemic conditioning in patients with acute myocardial infarction

Effects of remote ischemic conditioning (RIC) in acute myocardial infarction (AMI) patients remain conflicting. We performed this meta-analysis of randomized clinical trials (RCTs) to evaluate the benefits of the RIC in patients with AMI. Potentially relevant RCTs were identified by searching PubMed, Embase, Cochrane Library, VIP, CNKI, and Wanfang database until November 2016. RCTs evaluating RIC using intermittent limb ischemia-reperfusion in AMI patients were included. Thirteen RCTs were identified and analyzed. Meta-analysis showed that RIC significantly reduced the area under the curve (AUC) of creatine kinase-myocardial band (CK-MB) (standardized mean difference [SMD] -0.29; 95% confidence intervals [CI] -0.44 to -0.14; P = 0.0002) and AUC of troponin T (SMD -0.22; 95% CI -0.37 to -0.08; P = 0.003). Risk ratio (RR) for ≥70% ST-segment resolution favored RIC group than the control group (RR 1.39; 95% CI 1.03-1.86; P = 0.03). RIC also significantly reduced all-cause mortality (RR 0.33; 95%CI 0.17-0.64; P = 0.001). Subgroup analyses on the CK-MB AUC and ST-segment resolution ≥70% rate showed that the effects of RIC appeared to be affected by the limb used, duration of RIC, and clinical setting. RIC may offer cardioprotective effects by improving ST-segment resolution and reducing the infarct size in AMI patients.

Ischaemic preconditioning for the reduction of renal ischaemia reperfusion injury

BACKGROUND

Ischaemia reperfusion injury can lead to kidney dysfunction or failure. Ischaemic preconditioning is a short period of deprivation of blood supply to particular organs or tissue, followed by a period of reperfusion. It has the potential to protect kidneys from ischaemia reperfusion injury.

OBJECTIVES

This review aimed to look at the benefits and harms of local and remote ischaemic preconditioning to reduce ischaemia and reperfusion injury among people with renal ischaemia reperfusion injury.

SEARCH METHODS

We searched Cochrane Kidney and Transplant's Specialised Register to 5 August 2016 through contact with the Information Specialist using search terms relevant to this review.

SELECTION CRITERIA

We included all randomised controlled trials measuring kidney function and the role of ischaemic preconditioning in patients undergoing a surgical intervention that induces kidney injury. Kidney transplantation studies were excluded.

DATA COLLECTION AND ANALYSIS

Studies were assessed for eligibility and quality; data were extracted by two independent authors. We collected basic study characteristics: type of surgery, remote ischaemic preconditioning protocol, type of anaesthesia. We collected primary outcome measurements: serum creatinine and adverse effects to remote ischaemic preconditioning and secondary outcome measurements: acute kidney injury, need for dialysis, neutrophil gelatinase-associated lipocalin, hospital stay and mortality. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes, and mean difference (MD) and 95% CI for continuous outcomes.

MAIN RESULTS

We included 28 studies which randomised a total of 6851 patients. Risk of bias assessment indicated unclear to low risk of bias for most studies. For consistency regarding the direction of effects, continuous outcomes with negative values, and dichotomous outcomes with values less than one favour remote ischaemic preconditioning. Based on high quality evidence, remote ischaemic preconditioning made little or no difference to the reduction of serum creatinine levels at postoperative days one (14 studies, 1022 participants: MD -0.02 mg/dL, 95% CI -0.05 to 0.02; I2 = 21%), two (9 studies, 770 participants: MD -0.04 mg/dL, 95% CI -0.09 to 0.02; I2 = 31%), and three (6 studies, 417 participants: MD -0.05 mg/dL, 95% CI -0.19 to 0.10; I2 = 68%) compared to control.Serious adverse events occurred in four patients receiving remote ischaemic preconditioning by iliac clamping. It is uncertain whether remote ischaemic preconditioning by cuff inflation leads to increased adverse effects compared to control because the certainty of the evidence is low (15 studies, 3993 participants: RR 3.47, 95% CI 0.55 to 21.76; I2 = 0%); only two of 15 studies reported any adverse effects (6/1999 in the remote ischaemic preconditioning group and 1/1994 in the control group), the remaining 13 studies stated no adverse effects were observed in either group.Compared to control, remote ischaemic preconditioning made little or no difference to the need for dialysis (13 studies, 2417 participants: RR 0.85, 95% CI 0.37 to 1.94; I2 = 60%; moderate quality evidence), length of hospital stay (8 studies, 920 participants: MD 0.17 days, 95% CI -0.46 to 0.80; I2 = 49%, high quality evidence), or all-cause mortality (24 studies, 4931 participants: RR 0.86, 95% CI 0.54 to 1.37; I2 = 0%, high quality evidence).Remote ischaemic preconditioning may have slightly improved the incidence of acute kidney injury using either the AKIN (8 studies, 2364 participants: RR 0.76, 95% CI 0.57 to 1.00; I2 = 61%, high quality evidence) or RIFLE criteria (3 studies, 1586 participants: RR 0.91, 95% CI 0.75 to 1.12; I2 = 0%, moderate quality evidence).

AUTHORS' CONCLUSIONS

Remote ischaemic preconditioning by cuff inflation appears to be a safe method, and probably leads to little or no difference in serum creatinine, adverse effects, need for dialysis, length of hospital stay, death and in the incidence of acute kidney injury. Overall we had moderate-high certainty evidence however the available data does not confirm the efficacy of remote ischaemic preconditioning in reducing renal ischaemia reperfusion injury in patients undergoing major cardiac and vascular surgery in which renal ischaemia reperfusion injury may occur.

Effects of Renal Ischemic Postconditioning on Myocardial Ultrastructural Organization and Myocardial Expression of Bcl-2/Bax in Rabbits

We investigated the cardioprotective effect of renal ischemic postconditioning (RI-PostC) and its mechanisms in a rabbit model. Rabbits underwent 60 min of left anterior descending coronary artery occlusion (LADO) and 6 h of reperfusion. The ischemia-reperfusion (IR) group underwent LADO and reperfusion only. In the RI-PostC group, the left renal artery underwent 3 cycles of occlusion for 30 seconds and release for 30 seconds, before the coronary artery was reperfused. In the RI-PostC + GF109203X group, the rabbits received 0.05 mg/kg GF109203X (protein kinase C inhibitor) intravenously for 10 min followed by RI-PostC. Light microscopy and electron microscopy demonstrated that the RI-PostC group showed less pronounced changes, a smaller infarct region, and less apoptosis than the other two groups. Bcl-2 and Bax protein expression did not differ between the IR and RI-PostC + GF109203X groups. However, in the RI-PostC group, Bcl-2 protein expression was significantly higher and Bax protein expression was significantly lower than in the other two groups (P < 0.05). Changes in heart rate and mean arterial pressure were also smaller in the RI-PostC group than in the other two groups. These results indicate that RI-PostC can ameliorate myocardial ischemia-reperfusion injury and increase the Bcl-2/Bax ratio through a mechanism involving protein kinase C.

MicroRNA-29a/b/c targets iNOS and is involved in protective remote ischemic preconditioning in an ischemia-reperfusion rat model of non-alcoholic fatty liver disease

Remote ischemic preconditioning (RIPC) protects against the injury that is incurred by ischemia and reperfusion (IR); however, the role of RIPC in liver IR injury in non-alcoholic fatty liver disease (NAFLD) remains unclear. In this study, a NAFLD rat model was utilized in a series of different surgical procedures and molecular experiments. Rats of the IR group and the RIPC+IR group exhibited more severe injury than NAFLD control rats (in which the liver was prodded following a median-incision laparotomy). The liver condition, measured by serum alanine transaminase and aspartate transaminase levels, of the RIPC+IR group was better than that of the IR group. In addition, alanine transaminase and aspartate transaminase levels were lower in the RIPC+IR group compared with the IR group (P<0.001). Flow cytometry revealed that the cell apoptosis ratio was significantly lower in the RIPC+IR group than in the IR group (P<0.001). Reverse transcription-polymerase chain reaction (RT-qPCR) was used to assess miR-29a/b/c levels, revealing that they were significantly reduced in the RIPC and RIPC+IR groups, but did not vary in the IR group compared with the control group. RT-qPCR also revealed that iNOS mRNA levels were not significantly different among any of the NAFLD groups; however, western blot analysis indicated that iNOS protein levels were increased in the RIPC group and the RIPC+IR group compared with the control and IR groups. A luciferase reporter assay demonstrated that transfection with miR-29a/b/c mimics significantly decreased the luciferase activities of plasmids containing the wild-type iNOS 3'-untranslated region (UTR) (relative fluorescence intensity: 0.47±0.06 for miR-29a, 0.36±0.07 for miR-29b, 0.41±0.04 for miR-29c; P<0.001), whereas the activities of plasmids containing the mutant iNOS 3'-UTR sequence were not markedly affected [relative fluorescence intensity: 0.99±0.08 for miR-29a (P=0.1349), 0.99±0.09 for miR-29b (P=0.1607), 0.97±0.07 for miR-29c (P=0.1824)]. This suggested that miR-29a/b/c downregulates iNOS by directly targeting its 3'-UTR. In summary, the results suggest that RIPC has a protective effect in NAFLD liver IR injury, which may be due to reduced miR-29a/b/c levels in the skeletal muscle, leading to increased iNOS and, therefore, nitric oxide.

Circadian variation in acute myocardial infarct size assessed by cardiovascular magnetic resonance in reperfused STEMI patients

OBJECTIVE

Clinical studies using serum cardiac biomarkers to investigate a circadian variation in acute myocardial infarct (MI) size in ST-segment elevation myocardial infarction (STEMI) patients reperfused by primary percutaneous coronary intervention (PPCI) have produced mixed results. We aimed to investigate this phenomenon using acute MI size measured by cardiovascular magnetic resonance (CMR).

METHODS

Patient-level data was obtained from 4 randomized controlled trials investigating the MI-limiting effects of cardioprotective therapies in this pooled analysis. The primary analysis was performed in those patients with no pre-infarct angina; duration of ischemia >60min and <360min; Thrombolysis In Myocardial Infarction (TIMI) flow pre-PPCI ≤1; TIMI flow post-PPCI 3; and no collateral flow.

RESULTS

169 out of 376 patients with CMR data met the inclusion criteria for the primary analysis. A 24-hour circadian variation in acute MI size as a % of the area-at-risk (%AAR), after adjusting for confounders, was observed with a peak and nadir MI size in patients with symptom onset between 00:00 and 01:00 and between 12:00 and 13:00 respectively (difference from the average MI size 5.2%, 95%CI 1.1-9.4%; p=0.013). This was associated with a non-significant circadian variation in left ventricular ejection fraction (LVEF) (difference from the average LVEF 5.9%, 95%CI -0.6-2.2%, p=0.073). There was no circadian variation in MI size or LVEF in the whole cohort.

CONCLUSIONS

We report a circadian variation in acute MI size assessed by CMR in a subset of STEMI patients treated by PPCI, with the largest and smallest MI size occurring in patients with symptom onset between 00:00 and 01:00 and between 12:00 and 13:00 respectively.

Effect of remote ischemic conditioning on infarct size in patients with anterior ST-elevation myocardial infarction

BACKGROUND

Previous studies indicate that remote ischemic conditioning performed before percutaneous coronary intervention (PCI) reduces infarct size in patients with ST-elevation myocardial infarction (STEMI). It remains unclear whether remote conditioning affords protection when performed in adjunct to primary PCI. We aimed to study whether remote ischemic per-postconditioning (RIperpostC) initiated after admission to the catheterization laboratory attenuates myocardial infarct size in patients with anterior STEMI.

METHODS

In this prospective multicenter trial 93 patients with anterior STEMI were randomized to RIperpostC or sham procedure as adjunct to primary PCI. RIperpostC was started on arrival in the catheterization laboratory by 5-minute cycles of inflation and deflation of a blood pressure cuff around the left thigh and continued throughout the PCI procedure. Infarct size and myocardium at risk were determined by cardiac magnetic resonance at day 4 to 7. The primary outcome was myocardial salvage index.

RESULTS

There was no significant difference in myocardial salvage index between the RIperpostC and control group (median 48.5% and interquartile range 30.9%-60.8% vs 49.2% [42.1%-58.8%]). Neither did absolute infarct size in relation to left ventricular myocardial volume differ significantly (RIperpostC 20.6% [14.1%-31.7%] vs control 17.9% [13.4%-25.0%]). The RIperpostC group had larger myocardial area at risk than the control group (43.1% (35.4%-49.7%) vs 37.0% (30.8%-44.1%) of the left ventricle, P=.03). Peak value and area under the curve for troponin T did not differ significantly between the study groups.

CONCLUSIONS

RIperpostC initiated after admission to the catheterization laboratory in patients with anterior STEMI did not confer protection against reperfusion injury.

[Cardioprotection via the arm? : How a blood pressure cuff decreases infarct sizes]

Cardiovascular diseases and especially myocardial infarctions are responsible for a high morbidity and mortality throughout Europe. An essential aspect of myocardial infarction is ischemia/reperfusion injury which represents the necrosis of myocytes following reperfusion. One possible option to counteract ischemia/reperfusion injury is the much researched process of remote ischemic conditioning (RIC), whereby a certain tissue (e.g. skeletal muscle) is subjected to several cycles of short periods (e.g. 5 min) of ischemia and reperfusion and leads to the protection of another organ (e.g. the heart). Despite substantial efforts to elucidate the underlying mechanisms during the last decades, this phenomenon is not yet completely understood. Clinical studies mainly concentrated on laboratory and radiological parameters, which led to better understanding of RIC; however, large clinical studies evaluating the possible influence on mortality are still lacking. This review article provides an introduction to RIC and summarizes the current understanding of known pathomechanisms and the results of important clinical studies.

Ischaemic conditioning and targeting reperfusion injury: a 30 year voyage of discovery

To commemorate the auspicious occasion of the 30th anniversary of IPC, leading pioneers in the field of cardioprotection gathered in Barcelona in May 2016 to review and discuss the history of IPC, its evolution to IPost and RIC, myocardial reperfusion injury as a therapeutic target, and future targets and strategies for cardioprotection. This article provides an overview of the major topics discussed at this special meeting and underscores the huge importance and impact, the discovery of IPC has made in the field of cardiovascular research.

Remote Limb Ischemic Conditioning at Two Cuff Inflation Pressures Yields Learning Enhancements in Healthy Adults

The authors tested whether 2 doses of remote limb ischemic conditioning (RLIC), induced via blood pressure cuff inflation, enhanced motor and cognitive learning to an equal extent, and explored a panel of blood biomarkers of RLIC. Thirty-two young adults were randomized to 3 groups and underwent a 7-day protocol of RLIC/sham followed by motor and cognitive training, with follow-up. Both RLIC groups had greater motor learning and a trend toward greater cognitive learning compared with the sham group. RLIC at the lower inflation pressure was as effective as RLIC with the higher inflation pressure. No significant candidate blood biomarkers were found. RLIC could be a well-tolerated method to enhance learning and improve rehabilitation outcomes in people with neurological conditions.

Effect of remote ischemic post-conditioning on oxidative stress in blood of STEMI patients treated with primary angioplasty

Introduction: This study designed to use remote ischemic post conditioning (RIPC) as a protective strategy during percutaneous coronary intervention (PCI) in patients with ST segment elevation myocardial infarction (STEMI) to reduce myocardial cells damage due to reperfusion injury. Methods: Sixty-one patients were divided into test group (32 patients) receiving RIPC and control group (29 patients). Patients were included with first MI who had 20-80 years old. The RIPC protocol was applied on patients arm in three successive episodes during the opening of infarct-related artery (IRA). Whole blood sample were taken from patients after the first episode before IRA opening and after the third episode after IRA opening. The serums were extracted and stored in the freezer -70˚C to determine the levels of glutathione peroxidase (GPX), superoxide dismutase (SOD), total antioxidant capacity (TAC) and malondialdehyde (MDA). Results: The levels of GPX and SOD after the first episode of RIPC were significantly higher in test group than control group (P < 0.001). Similar alterations of these enzymes were obtained after IRA opening (after third episode). In addition, the levels of TAC remained unchanged in control patients but it was significantly increased after the third episode of RIPC in test patients (P < 0.001). Finally, the MDA level was increased in control group in comparison with test group, and administration of RIPC in test group prevented the enhancement of MDA levels significantly (P < 0.001). Conclusion: The results indicated that RIPC protocol has protective properties in patients with STEMI through enhancing the antioxidant potentials and decreasing lipid peroxidation.

Review of remote ischemic preconditioning: from laboratory studies to clinical trials

In remote ischemic preconditioning (RIPC) short periods of non-lethal ischemia followed by reperfusion of tissue or organ prepare remote tissue or organ to resist a subsequent more severe ischemia-reperfusion injury. The signaling mechanism of RIPC can be humoral communication, neuronal stimulation, systemic modification of circulating immune cells, and activation of hypoxia inducible genes. Despite promising evidence from experimental studies, the clinical effects of RIPC have been controversial. Heterogeneity of inclusion and exclusion criteria and confounding factors such as comedication, anesthesia, comorbidities, and other risk factors may have influenced the efficacy of RIPC. Although the cardioprotective pathways of RIPC are more widely studied, there is also evidence of benefits in CNS, kidney and liver protection. Future research should explore the potential of RIPC, not only in cardiac protection, but also in patients with threatening ischemia of the brain, organ transplantation of the heart, liver and kidney and extensive cardiovascular surgery. RIPC is generally well-tolerated, safe, effective, and easily feasible. It has a great prospect for ischemic protection of the heart and other organs.

Time to Give Up on Cardioprotection?

The mortality from acute myocardial infarction (AMI) remains significant, and the prevalence of post-myocardial infarction heart failure is increasing. Therefore, cardioprotection beyond timely reperfusion is needed. Conditioning procedures are the most powerful cardioprotective interventions in animal experiments. However, ischemic preconditioning cannot be used to reduce infarct size in patients with AMI because its occurrence is not predictable; several studies in patients undergoing surgical coronary revascularization report reduced release of creatine kinase and troponin. Ischemic postconditioning reduces infarct size in most, but not all, studies in patients undergoing interventional reperfusion of AMI, but may require direct stenting and exclusion of patients with >6 hours of symptom onset to protect. Remote ischemic conditioning reduces infarct size in patients undergoing interventional reperfusion of AMI, elective percutaneous or surgical coronary revascularization, and other cardiovascular surgery in many, but not in all, studies. Adequate dose-finding phase II studies do not exist. There are only 2 phase III trials, both on remote ischemic conditioning in patients undergoing cardiovascular surgery, both with neutral results in terms of infarct size and clinical outcome, but also both with major problems in trial design. We discuss the difficulties in translation of cardioprotection from animal experiments and proof-of-concept trials to clinical practice. Given that most studies on ischemic postconditioning and all studies on remote ischemic preconditioning in patients with AMI reported reduced infarct size, it would be premature to give up on cardioprotection.

Remote ischemic postconditioning protects against renal ischemia/reperfusion injury by activation of T-LAK-cell-originated protein kinase (TOPK)/PTEN/Akt signaling pathway mediated anti-oxidation and anti-inflammation

BACKGROUND

Recent clinical and animal studies suggested that remote limb ischemic postconditioning (RIPostC) can invoke potent cardioprotection or neuroprotection. However, the effect and mechanism of RIPostC against renal ischemia/reperfusion injury (IRI) are poorly understood. T-LAK-cell-originated protein kinase (TOPK) is crucial for the proliferation and migration of tumor cells. However, the function of TOPK and the molecular mechanism underlying renal protection remain unknown. Therefore, this study aimed to evaluate the role of TOPK in renoprotection induced by RIPostC.

MATERIALS AND METHODS

The renal IRI model was induced by left renal pedicle clamping for 45min followed by 24h reperfusion and right nephrectomy. All mice were intraperitoneally injected with vehicle, TOPK inhibitor HI-TOPK-032 or Akt inhibitor LY294002. After 24h reperfusion, renal histology, function, and inflammatory cytokines and oxidative stress were assessed. The proteins were measured by Western blotting.

RESULTS

The results showed that RIPostC significantly protected the kidneys against IRI. The protective effects were accompanied by the attenuation of renal dysfunction, tubular damage, inflammation and oxidative stress. In addition, RIPostC increased the phosphorylation of TOPK, PTEN, Akt, GSK3β and the nuclear translocation of Nrf2 and decreased the nuclear translocation of NF-κB. However, all of the above renoprotective effects of RIPostC were eliminated either by the inhibition of TOPK or Akt with HI-TOPK-032 or LY294002.

CONCLUSIONS

The current data reveal that RIPostC protects against renal IRI via activation of TOPK/PTEN/Akt signaling pathway mediated anti-oxidation and anti-inflammation.

Unraveling the role of adenosine in remote ischemic preconditioning-induced cardioprotection

Remote ischemic preconditioning (RIPC) induced by alternate cycles of preconditioning ischemia and reperfusion protects the heart against sustained ischemia-reperfusion-induced injury. This technique has been translated to clinical levels in patients undergoing various surgical interventions including coronary artery bypass graft surgery, abdominal aortic aneurysm repair, percutaneous coronary intervention and heart valve surgery. Adenosine is a master regulator of energy metabolism and reduces myocardial ischemia-reperfusion-induced injury. Furthermore, adenosine is a critical trigger as well as a mediator in RIPC-induced cardioprotection and scientists have demonstrated the role of adenosine by showing an increase in its levels in the systemic circulation during RIPC delivery. Furthermore, the blockade of cardioprotective effects of RIPC in the presence of specific adenosine receptor blockers and transgenic animals with targeted ablation of A1 receptors has also demonstrated its critical role in RIPC. The studies have shown that adenosine may elicit cardioprotection via activation of neurogenic pathway. The present review describes the possible role and mechanism of adenosine in mediating RIPC-induced cardioprotection.

Ischemia reperfusion injury as a modifiable therapeutic target for cardioprotection or neuroprotection in patients undergoing cardiopulmonary resuscitation

AIMS

We sought to review cellular changes that occur with reperfusion to try to understand whether ischemia-reperfusion injury (RI) is a potentially modifiable therapeutic target for cardioprotection or neuroprotection in patients undergoing cardiopulmonary resuscitation.

DATA SOURCES

Articles written in English and published in PubMed.

RESULTS

Remote ischemic conditioning (RIC) involves brief episodes of non-lethal ischemia and reperfusion applied to an organ or limb distal to the heart and brain. Induction of hypothermia involves cooling an ischemic organ or body. Both have pluripotent effects that reduce the potential harm associated with RI in the heart and brain by reduced opening of the mitochondrial permeability transition pore. Recent trials of RIC and induced hypothermia did not demonstrate these treatments to be effective. Assessment of the effect of these interventions in humans to date may have been modified by use of concurrent medications including propofol.

CONCLUSIONS

Ongoing research is necessary to assess whether reduction of RI improves patient outcomes.

Remote Ischemic Conditioning: Its Benefits and Limitations

This editorial describes benefits and limitations of remote ischemic conditioning. Remote ischemic conditioning was shown to reduce myocardial intact size in at least 4 sizeable clinical trials of acute myocardial infarction. It was not effective in recent studies of cardiac surgery. Reasons for these differences are discussed.

Remote ischemic conditioning for kidney protection: A meta-analysis

BACKGROUND

Results from randomized controlled trials (RCTs) concerning kidney effect of remote ischemic conditioning (RIC) are inconsistent.

METHODS

We searched for relevant studies in Medline, Embase, the Cochrane Library, Google Scholar and Chinese database (SinoMed), as well as relevant references from their inception to November 2015. We performed a systematic review and meta-analysis of all eligible RCTs of RIC with kidney events.

RESULTS

We included 37 RCTs from 2007 to 2015 involving 8168 patients. Pooled analyses of all RCTs showed RIC significantly reduced the incidence of investigator-defined acute kidney injury (AKI) compared with control groups (RR 0.84, 95% CI 0.73-0.96, P = .009) (I(2) = 25%). However, the difference was not significant when only RIFLE (Risk, Injury, Failure, Loss, End Stage), AKIN (Acute Kidney Injury Network), or KDIGO (Kidney Disease Improving Global Outcomes) criteria were applied to the definition of AKI (RR 0.87, 95% CI 0.74-1.02, P = .08) (I(2) = 22%). In subgroup analysis, RIC showed a significant benefit on reducing investigator-defined AKI in patients following percutaneous coronary intervention (RR 0.64, 95% CI 0.46-0.87), but not after cardiac surgery (RR 0.93, 95% CI 0.82-1.06). There was no difference for changes in the incidence of renal replacement therapy, estimated glomerular filtration rate or serum creatinine.

CONCLUSIONS

RIC might be beneficial for the prevention of investigator-defined AKI; however, the effect is likely small. Moreover, due to lack of an effect on use of renal replacement therapy, estimated glomerular filtration rate, RIFLE, AKIN, or KDIGO-defined AKI, and serum creatinine, the evidence for RIC is not robust. Finally, recent large-scale RCTs of RIC focusing on patient-centered outcomes do not support the wider application of RIC.

Hypoxemic reperfusion of ischemic states: an alternative approach for the attenuation of oxidative stress mediated reperfusion injury

Ischemia and reperfusion (I/R) - induced injury has been described as one of the main factors that contribute to the observed morbidity and mortality in a variety of clinical entities, including myocardial infarction, ischemic stroke, cardiac arrest and trauma. An imbalance between oxygen demand and supply, within the organ beds during ischemia, results in profound tissue hypoxia. The subsequent abrupt oxygen re-entry upon reperfusion, may lead to a burst of oxidative aggression through production of reactive oxygen species by the primed cells. The predominant role of oxidative stress in the pathophysiology of I/R mediated injury, has been well established. A number of strategies that target the attenuation of the oxidative burst have been tested both in the experimental and the clinical setting. Despite these advances, I/R injury continues to be a major problem in everyday medical practice. The aim of this paper is to review the existing literature regarding an alternative approach, termed hypoxemic reperfusion, that has exhibited promising results in the attenuation of I/R injury, both in the experimental and the clinical setting. Further research to clarify its underlying mechanisms and to assess its efficacy in the clinical setting is warranted.

Pacing Postconditioning: Recent Insights of Mechanism of Action and Probable Future Clinical Application

Ischemic heart disease, also known as coronary heart disease or coronary artery disease, accounts for >50% of cardiovascular events and is a leading cause worldwide of morbidity and mortality. Hypoperfusion of the heart is the major cause of injury in ischemic heart disease, as it results in the death of cardiomyoctes due to a lack of oxygen and energy. This injury ultimately leads to a dead area in the heart called infarcted area or myocardial infarction. The formation of myocardial infarction leads to a lengthy process of remodeling which causes many changes in the architecture and the electrophysiology of the heart. These changes may eventually lead to death due to arrhythmia or heart failure. Tremendous efforts have been made over the last decades to decrease the burden of ischemic reperfusion (I/R) injury. The first salvage to the ischemic heart is reperfusion; however, this procedure is associated with a subsequent reperfusion injury. In the 1980s, a method known as preconditioning was introduced and showed great potential in combating ischemic heart disease, but this technique is limited by the difficulty of its translation to the clinic as it requires the anticipation of an occurrence of ischemic heart disease. Not long after, a new method, postconditioning, was introduced. This method showed great success, and several studies were performed to investigate its signaling cascades and the possibility of its translation to the clinic. Thereafter, several trials were made, and many methods of postconditioning were developed. One of these is intermittent dyssynchrony, pacing postconditioning (PPC), of the heart, which involves brief episodes of electrical pacing. PPC afforded a pronounced protection to the heart against I/R injury, similar to that afforded by pre- and postconditioning.

Reducing myocardial infarct size: challenges and future opportunities

Despite prompt reperfusion by primary percutaneous coronary intervention (PPCI), the mortality and morbidity of patients presenting with an acute ST-segment elevation myocardial infarction (STEMI) remain significant with 9% death and 10% heart failure at 1 year. In these patients, one important neglected therapeutic target is ‘myocardial reperfusion injury’, a term given to the cardiomyocyte death and microvascular dysfunction which occurs on reperfusing ischaemic myocardium. A number of cardioprotective therapies (both mechanical and pharmacological), which are known to target myocardial reperfusion injury, have been shown to reduce myocardial infarct (MI) size in small proof-of-concept clinical studies—however, being able to demonstrate improved clinical outcomes has been elusive. In this article, we review the challenges facing clinical cardioprotection research, and highlight future therapies for reducing MI size and preventing heart failure in patients presenting with STEMI at risk of myocardial reperfusion injury.

From Protecting the Heart to Improving Athletic Performance - the Benefits of Local and Remote Ischaemic Preconditioning

Remote Ischemic Preconditioning (RIPC) is a non-invasive cardioprotective intervention that involves brief cycles of limb ischemia and reperfusion. This is typically delivered by inflating and deflating a blood pressure cuff on one or more limb(s) for several cycles, each inflation-deflation being 3-5 min in duration. RIPC has shown potential for protecting the heart and other organs from injury due to lethal ischemia and reperfusion injury, in a variety of clinical settings. The mechanisms underlying RIPC are under intense investigation but are just beginning to be deciphered. Emerging evidence suggests that RIPC has the potential to improve exercise performance, via both local and remote mechanisms. This review discusses the clinical studies that have investigated the role of RIPC in cardioprotection as well as those studying its applicability in improving athletic performance, while examining the potential mechanisms involved.

Approaches to Improving Cardiac Structure and Function During and After an Acute Myocardial Infarction: Acute and Chronic Phases

While progress has been made in improving survival following myocardial infarction, this injury remains a major source of mortality and morbidity despite modern reperfusion therapy. While one approach has been to develop therapies to reduce lethal myocardial cell reperfusion injury, this concept has not translated to the clinics, and several recent negative clinical trials raise the question of whether reperfusion injury is important in humans undergoing reperfusion for acute ST segment elevation myocardial infarction. Therapy aimed at reducing myocardial cell death while the myocytes are still ischemic is more likely to further reduce myocardial infarct size. Developing new therapies to further reduce left ventricular remodeling after the acute event is another approach to preserving structure and function of the heart after infarction. Such therapy may include chronic administration of pharmacologic agents and/or therapies developed from the field of regenerative cardiology, including cellular or non-cellular materials such as extracellular matrix. The optimal therapy will be to administer agents that both reduce myocardial infarct size in the acute phase of infarction as well as reduce adverse left ventricular remodeling during the chronic or healing phase of myocardial infarction. Such a dual approach will help optimize the preservation of both cardiac structure and function.

Short-and long-term effects of ischemic postconditioning in STEMI patients: a meta-analysis

Background

Compelling evidence from large randomized trials demonstrates the salutary effects of ischemic postconditioning on cardioprotection against ischemic/reperfusion injury. However, some studies appear negative findings.

This study was designed to assess the short-and long-term effects of postconditioning (Poc) in studies including evolving ST-elevation myocardial infarction (STEMI).

Methods

Relevant studies were identified through an electronic literature search from the PubMed, Library of Congress, Embase, Cochrane Central Register of Controlled Trials, and ISI Web of Science. Studies published up to December 2014 were eligible for inclusion. Patients older than 18 years presenting within 12 h of the first STEMI and eligible for angioplasty were considered for the study.

Results

The 25 trials allocated 1136 patients to perform locational postconditioning cycles at the onset of reperfusion and 1153 patients to usual percutaneous coronary intervention (PCI). Ischemic postconditioning demonstrated a decrease in serum cardiac enzymes creatine kinase (CK) and CK-MB (P < 0.00001 and P =0.25, respectively) in the subgroup analysis based on direct stenting. Reduction in infarct size by imaging was showed during7 days after myocardial infarction (P =0.01), but not in the longterm (P = 0.08). The wall motion score index was improved in both the short term within 7 days (P = 0.009) and the long term over 6 months after receiving Poc (P = 0.02). All included studies were limited by the high risk of performance and publication bias.

Conclusions

Ischemic postconditioning by brief interruptions of coronary blood flow at the onset of reperfusion after PCI appears to be superior to PCI alone in reducing myocardial injury and improving left ventricular function, especially in patients who have received direct stenting in PCI.

Interaction of risk factors, comorbidities, and comedications with ischemia/reperfusion injury and cardioprotection by preconditioning, postconditioning, and remote conditioning

Pre-, post-, and remote conditioning of the myocardium are well described adaptive responses that markedly enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and provide therapeutic paradigms for cardioprotection. Nevertheless, more than 25 years after the discovery of ischemic preconditioning, we still do not have established cardioprotective drugs on the market. Most experimental studies on cardioprotection are still undertaken in animal models, in which ischemia/reperfusion is imposed in the absence of cardiovascular risk factors. However, ischemic heart disease in humans is a complex disorder caused by, or associated with, cardiovascular risk factors and comorbidities, including hypertension, hyperlipidemia, diabetes, insulin resistance, heart failure, altered coronary circulation, and aging. These risk factors induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury per se and responses to cardioprotective interventions. Moreover, some of the medications used to treat these risk factors, including statins, nitrates, and antidiabetic drugs, may impact cardioprotection by modifying cellular signaling. The aim of this article is to review the recent evidence that cardiovascular risk factors and their medication may modify the response to cardioprotective interventions. We emphasize the critical need to take into account the presence of cardiovascular risk factors and concomitant medications when designing preclinical studies for the identification and validation of cardioprotective drug targets and clinical studies. This will hopefully maximize the success rate of developing rational approaches to effective cardioprotective therapies for the majority of patients with multiple risk factors.

Cardioprotection by combined intrahospital remote ischaemic perconditioning and postconditioning in ST-elevation myocardial infarction: the randomized LIPSIA CONDITIONING trial

AIMS

Remote ischaemic conditioning (RIC) and postconditioning (PostC) are both potent activators of innate protection against ischaemia-reperfusion injury and have demonstrated cardioprotection in experimental and clinical ST-elevation myocardial infarction (STEMI) trials. However, their combined effects have not been studied in detail. The aim of this study was to evaluate if the co-application of intrahospital RIC and PostC has a more powerful effect on myocardial salvage compared with either PostC alone or control.

METHODS AND RESULTS

This prospective, controlled, single-centre study randomized 696 STEMI patients to one of the following three groups: (i) combined intrahospital RIC + PostC in addition to primary percutaneous coronary intervention (PCI); (ii) PostC in addition to PCI; and (iii) conventional PCI (control). The primary endpoint myocardial salvage index was assessed by cardiac magnetic resonance (CMR) imaging within 3 days after infarction. Secondary endpoints included infarct size and microvascular obstruction (MVO) assessed by CMR. The combined clinical endpoint consisted of death, reinfarction, and new congestive heart failure within 6 months. The primary endpoint myocardial salvage index was significantly greater in the combined RIC + PostC group when compared with the control group (49 [interquartile range 30-72] vs. 40 [interquartile range 16-68], P = 0.02). Postconditioning alone failed to improve myocardial salvage when compared with conventional PCI (P = 0.39). The secondary endpoints, including infarct size and MVO, showed no significant differences between groups. Clinical follow-up at 6 months revealed no differences in the combined clinical endpoint between groups (P = 0.44).

CONCLUSION

Combined intrahospital RIC + PostC in conjunction with PCI in STEMI significantly improves myocardial salvage in comparison with control and PostC.

CLINICALTRIALSGOV

NCT02158468.

Coronary microvascular obstruction in acute myocardial infarction

The success of a primary percutaneous intervention (PCI) in the setting of ST elevation myocardial infarction depends on the functional and structural integrity of coronary microcirculation. Coronary microvascular dysfunction and obstruction (CMVO) occurs in up to half of patients submitted to apparently successful primary PCI and is associated to a much worse outcome. The current review summarizes the complex mechanisms responsible for CMVO, including pre-existing coronary microvascular dysfunction, and highlights the current limitations in the assessment of microvascular function. More importantly, at the light of the substantial failure of trials hitherto published on the treatment of CMVO, this review proposes a novel integrated therapeutic approach, which should overcome the limitations of previous studies.