Late remote ischemic preconditioning provides benefit to patients undergoing elective percutaneous coronary intervention

Effect of perioperative remote ischemic conditioning on myocardial injury in patients with unstable angina undergoing percutaneous coronary intervention: protocol of a multicenter, randomized, double-blind clinical trial

BACKGROUND

Cardiovascular disease is a leading cause of death, with ischemic heart disease being a significant contributor. While percutaneous coronary intervention (PCI) effectively reduces mortality in myocardial infarction patients, its efficacy for unstable angina (UA) patients is controversial. Complications associated with PCI further limit application in UA. RIC is hypothesized to be an effective co-intervention that reduces PCI-related complications and may potentially enhance the efficacy of the PCI procedure itself.

METHODS

This is a pragmatic, prospective, dual-center, double-blind, randomized controlled clinical trial assessing the effect of remote ischemic conditioning (RIC) during percutaneous coronary intervention (PCI) on injury in unstable angina patients aged ≥ 18 years undergoing coronary angiography. Participants will be randomized to receive either RIC or Sham RIC, in addition to standard pharmacotherapy. Primary outcome includes periprocedural myocardial injury measured by hs-cTnT levels, while secondary outcomes encompass major adverse cardiovascular events, coronary artery lesions Gensini Score, arrhythmia, angina incidence, SAQ scores, ECG changes, and cardiac function assessed by two-dimensional echocardiography. The trial aims to recruit 574 participants and is scheduled to be initiated on 15 January 2024. We will conduct the primary statistical analysis using the intention-to-treat principle. Results from the trial will be presented as comparative summary statistics following the Consolidated Standards of Reporting Trials (CONSORT) guidelines.

TRIAL REGISTRATION

ChiCTR2400079855, 15 January 2024.

Application Value of Limb Ischemic Preconditioning in Preventing Intradialytic Hypotension during Maintenance Hemodialysis

INTRODUCTION

The aim of this study was to investigate the efficacy and safety of limb ischemia preconditioning (LIPC) in the treatment of intradialytic hypotension (IDH) in patients with maintenance hemodialysis (MHD).

METHODS

This was a single-center, prospective, and randomized controlled case study. A total of 38 patients with MHD who met the inclusion criteria from September 2021 to August 2022 were selected from the Blood Purification Center of our hospital. They were randomly divided into the LIPC group (n = 19) and the control group (n = 19). For patients in the LIPC group, the femoral artery blood flow was blocked with an LIPC instrument for 5 min (pressurized to 200 mm Hg) before each dialysis, and they were reperfused for 5 min. The cycle was repeated five times, with a total of 50 min for 12 weeks. The control group was pressurized to 20 mm Hg with an LIPC instrument, and the rest was the same as the LIPC group. The blood pressure of 0 h, 1 h, 2 h, 3 h, 4 h, and body weight before and after hemodialysis were measured in the two groups during hemodialysis, the incidence of IDH and the changes of serum troponin I (TNI) and creatine kinase isoenzyme MB (CK-MB) levels before and after the intervention were observed, and the ultrafiltration volume and ultrafiltration rate were recorded.

RESULTS

At the 8th and 12th week after intervention, the MAP in the LIPC group was higher than that in the control group (103.28 ± 12.19 mm Hg vs. 93.18 ± 11.11 mm Hg, p = 0.04; 101.81 ± 11.36 mm Hg vs. 91.81 ± 11.92 mm Hg, p = 0.047). The incidence of IDH in the LIPC group was lower than that in the control group (36.5% vs. 43.1%, p = 0.01). The incidence of clinical treatment in IDH patients in the LIPC group was lower than that in the control group (6.3% vs. 12.4%, p = 0.00). The incidence of early termination of hemodialysis in the LIPC group was lower than that in the control group (1.6% vs. 3.8%, p = 0.01). The levels of TNI and CK-MB in the LIPC group after the intervention were lower than those in the control group (322.30 ± 13.72 ng/dL vs. 438.50 ± 24.72 ng/dL, p = 0.00; 159.78 ± 8.48 U/dL vs. 207.00 ± 8.70 U/dL, p = 0.00). The changes of MAP before and after the intervention were negatively correlated with the changes of TNI and CK-MB before and after the intervention (r = -0.473, p = 0.04; r = -0.469, p = 0.04). There were no differences in dry body mass and ultrafiltration rate between the two groups before and after the LIPC intervention (p > 0.05). Multiple linear regression analysis shows that TNI is the main influencing factor of ΔMAP. No LIPC-related adverse events were found during the study period.

CONCLUSION

LIPC can effectively reduce the incidence of IDH in patients with MHD and may be associated with the alleviation of myocardial damage.

The Protective Mechanism of Dexmedetomidine on Renal in Hemorrhagic Shock

Objective

To explore the protective effect of dexmedetomidine on renal function in patients with hemorrhagic shock and its possible mechanism.

Methods

Seventy patients with traumatic hemorrhagic shock requiring surgical treatment were randomly divided into the control group (group C) and the dexmedetomidine group (group D), with 35 patients in each group. Patients in both groups were actively treated with volumetric resuscitation while surgical hemostasis. Group D was given dexmedetomidine 0.5 μg/kg before skin incision after anesthesia induction, for 10 min, followed by intravenous infusion at a rate of 0.4 μg·kg⁻¹·h⁻¹ until 30 min before surgery, and group C was given equal volume of normal saline before skin resection (H1). Venous blood was collected 2 h (H2) and 4 h (H4) after skin resection, and plasma levels of BUN, creatinine (SCr), lipid peroxides (MDA), and inflammatory mediators IL-6 and IL-8 were measured on the 1st and 2nd day after surgery.

Results

Compared with H1, BUN and SCr levels had no significant difference at 2 h and 4 h after skin resection but significantly decreased at 1 and 2 postoperative days (D1) (P < 0.05). There were significant differences in MDA, IL-6, and IL-8 at 2 and 4 h after skin resection (P < 0.05), but there were no significant differences at 1 day after surgery (D1) and 2 days after surgery (D2). Compared with group C, the levels of MDA, IL-6, and IL-8 in group U were significantly decreased at 2 h and 4 h after skin resection (P < 0.05), and the levels of BUN and SCr in group U were significantly decreased at 1 and 2 days after skin resection (P < 0.05).

Conclusion

Dexmedetomidine can effectively inhibit the release of oxygen free radicals in the shock stage and the shock recovery stage in patients with hemorrhagic trauma shock and has a protective effect on renal function.

Can Clinical and Functional Outcomes Be Improved with an Intelligent "Internet Plus"-Based Full Disease Cycle Remote Ischemic Conditioning Program in Acute ST-elevation Myocardial Infarction Patients Undergoing Percutaneous Coronary Intervention? Rationale and Design of the i-RIC Trial

BACKGROUND

Acute ST-elevation myocardial infarction (STEMI) is associated with a high incidence of complications as well as a considerable hospitalization rate and economic burden. Preliminary evidence suggests that remote ischemic conditioning (RIC) is a promising non-invasive intervention that may effectively and safely reduce myocardial infarct size, subsequent cardiac events and complications, and mortality. However, RIC's cardio-protective effect remains under debate, especially for single timepoint RIC programs. Adequately powered large-scale randomized controlled trials investigating clinical outcomes are thus needed to clarify the role of full disease cycle RIC programs.

METHODS

The intelligent "Internet Plus"-based full disease cycle remote ischemic conditioning (i-RIC) trial is a pragmatic, multicenter, randomized controlled, parallel group, clinical trial. The term, intelligent "Internet Plus"-based full disease cycle, refers to smart devices aided automatic and real-time monitoring of remote ischemic pre-, per- or post-conditioning intervention for patients with STEMI undergoing percutaneous coronary intervention (PCI). Based on this perspective, 4700 STEMI patients from five hospitals in China will be randomized to a control and an intervention group. The control group will receive PCI and usual care, including pharmacotherapy, before and after PCI. The intervention group will receive pre-, per-, and post-operative RIC combined with long-term i-RIC over a one-month period in addition. A smartphone application, an automated cuff inflation/deflation device and "Internet Plus"-based administration will be used in the long-term phase. The primary outcome is the combined cardiac death or hospitalization for heart failure rate. Secondary outcomes include clinical and functional outcomes: major adverse cardiac and cerebrovascular events rate, all-cause mortality, myocardial reinfarction rate, readmission rate for heart failure and ischemic stroke rate, unplanned revascularization rate, plasma concentration of myocardial infarction-related key biomarkers, infarct size, cardiac function, cardiopulmonary endurance, health-related quality of life, total hospital length of stay, total medical cost, and compliance with treatment regime.

DISCUSSION

The i-RIC trial is designed to test the hypothesis that clinical and functional outcomes can be improved with the i-RIC program in STEMI patients undergoing PCI. The concept of RIC is expected to be enhanced with this intelligent "Internet Plus"-based program focusing on the full disease cycle. If the i-RIC program results in superior improvement in primary and secondary outcomes, it will offer an innovative treatment option for STEMI patients and form the basis of future recommendations.

CLINICAL TRIAL REGISTRATION

Chinese Clinical Trial Registry ( http://www.chictr.org.cn ): ChiCTR2000031550, 04 April 2020.

The Future of Cardioprotection-Pointing Toward Patients at Elevated Risk as the Target Populations

Translation of the cardioprotective effect by pharmacological and mechanical conditioning therapies into improvement of clinical outcome for the patients has been disappointing. Confounding factors like comorbidity and comedications may explain some of the loss in translation. However, the substantial improvement of outcome in disease states involving ischemia-reperfusion injury, that is, planned cardiac surgery, elective percutaneous coronary intervention, and even primary percutaneous coronary intervention for ST-segment myocardial infarction (STEMI), is the most plausible explanation for the missed demonstration of a clinical benefit. Remote ischemic conditioning has demonstrated consistent cardioprotective effect in experimental and in clinical proof-of-concept studies. As an adjunctive cardioprotective treatment beyond reperfusion, remote ischemic conditioning should address target populations at risk of extensive tissue damage, including patients who experience complications, which may induce profound myocardial ischemia in relation to cardiac surgery or elective percutaneous coronary intervention. Moreover, patients with STEMI and predictable impaired clinical outcome due to delayed hospital admission, high Killip class, cardiogenic shock, and cardiac arrest remain target groups. For high-risk patients, daily remote ischemic conditioning or the corollary of blood flow-restricted exercise may be alternative cardioprotective options during postoperative and post-myocardial infarct rehabilitation.

Remote ischemic preconditioning inhibits platelet αIIb β3 activation in coronary artery disease patients receiving dual antiplatelet therapy: A randomized trial

OBJECTIVES

We investigated whether remote ischemic preconditioning (RIPC) inhibits agonist-induced conformational activation of platelet αIIb β3 in patients with coronary artery disease already receiving conventional antiplatelet therapy.

PATIENTS/METHODS

Consecutive patients with angiographically confirmed coronary artery disease were randomized to RIPC or sham treatment. Venous blood was collected before and immediately after RIPC/sham. Platelet aggregometry (ADP, arachidonic acid) and whole blood platelet flow cytometry was performed for CD62P, CD63, active αIIb β3 (PAC-1 binding) before and after stimulation with ADP, thrombin ± collagen, or PAR-1 thrombin receptor agonist.

RESULTS

Patients (25 RIPC, 23 sham) were well matched, 83% male, age (mean ± standard deviation) 63.3 ± 13.2 years, 95% aspirin, 81% P2Y12 inhibitor. RIPC did not affect platelet aggregation, nor agonist-induced expression of CD62P, but selectively and significantly decreased αIIb β3 activation after stimulation with either PAR-1 agonist peptide or the combination of thrombin + collagen, but not after ADP nor thrombin alone. The effect of RIPC on platelet αIIb β3 activation was evident in patients receiving both aspirin and P2Y12 inhibitor, and was not associated with an increase in vasodilator-stimulated phosphoprotein phosphorylation.

CONCLUSIONS

Remote ischemic preconditioning inhibits conformational activation of platelet αIIb β3 in response to exposure to thrombin and collagen in patients with coronary artery disease receiving dual antiplatelet therapy. These findings indicate agonist-specific inhibition of platelet activation by RIPC in coronary artery disease that is not obviated by the prior use of P2Y12 inhibitors.

Remote ischemic conditioning: a promising therapeutic intervention for multi-organ protection

Despite decades of formidable exploration, multi-organ ischemia-reperfusion injury (IRI) encountered, particularly amongst elderly patients with clinical scenarios, such as age-related arteriosclerotic vascular disease, heart surgery and organ transplantation, is still an unsettled conundrum that besets clinicians. Remote ischemic conditioning (RIC), delivered via transient, repetitive noninvasive IR interventions to distant organs or tissues, is regarded as an innovative approach against IRI. Based on the available evidence, RIC holds the potential of affording protection to multiple organs or tissues, which include not only the heart and brain, but also others that are likely susceptible to IRI, such as the kidney, lung, liver and skin. Neuronal and humoral signaling pathways appear to play requisite roles in the mechanisms of RIC-related beneficial effects, and these pathways also display inseparable interactions with each other. So far, several hurdles lying ahead of clinical translation that remain to be settled, such as establishment of biomarkers, modification of RIC regimen, and deep understanding of underlying minutiae through which RIC exerts its powerful function. As this approach has garnered an increasing interest, herein, we aim to encapsulate an overview of the basic concept and postulated protective mechanisms of RIC, highlight the main findings from proof-of-concept clinical studies in various clinical scenarios, and also to discuss potential obstacles that remain to be conquered. More well designed and comprehensive experimental work or clinical trials are warranted in future research to confirm whether RIC could be utilized as a non-invasive, inexpensive and efficient adjunct therapeutic intervention method for multi-organ protection.

Remote ischaemic conditioning for myocardial infarction or elective PCI: systematic review and meta-analyses of randomised trials

BACKGROUND

The efficacy of remote ischaemic conditioning in clinical trials of ST-segment elevation myocardial infarction (STEMI) or elective percutaneous coronary intervention is controversial. We aimed to systematically review and meta-analyse whether remote ischaemic conditioning reduces myocardial damage in those patients.

METHODS

We searched PubMed, Embase and Web of Science from inception until December 2017 for randomised clinical trials evaluating remote ischaemic conditioning versus a control group. Two independent reviewers extracted data of 23 trials (2118 patients with STEMI; 2048 patients undergoing elective percutaneous coronary intervention) which were meta-analysed using random-effects models.

RESULTS

Remote ischaemic conditioning reduced infarct size in STEMI patients when assessed by imaging (mean difference of infarct size as percentage of left ventricle -2.43, 95% confidence interval (CI) -4.37 to -0.48; P=0.01; I²=44%; n=925) or biomarkers related to myocardial injury (peak values of cardiac biomarker release reported as standardised mean difference -0.19, 95% CI -0.37 to -0.02; P=0.03; I²=58%; n=1483) and increased myocardial salvage index (mean difference 0.07, 95% CI 0.01 to 0.13; P=0.02; I²=49%; n= 636). Left ventricular ejection fraction was increased when assessed during the first days after STEMI (mean difference 1.53, 95% CI 0.23 to 2.83; P=0.02; I²=28%; n=1192). Remote ischaemic conditioning had no influence on biomarker values after elective percutaneous coronary intervention (standardised mean difference 0.06, 95% CI -0.17 to 0.30; P=0.59).

CONCLUSIONS

Despite a statistically significant reduction of myocardial damage in STEMI patients, the magnitude of the reduction was small and a significant impact on clinical events is unlikely. With respect to elective percutaneous coronary intervention, remote ischaemic conditioning had no influence on myocardial injury and its use is not supported by our analysis.

Clinical translation of myocardial conditioning

Rapid admission and acute interventional treatment combined with modern antithrombotic pharmacologic therapy have improved outcomes in patients with ST elevation myocardial infarction. The next major target to further advance outcomes needs to address ischemia-reperfusion injury, which may contribute significantly to the final infarct size and hence mortality and postinfarction heart failure. Mechanical conditioning strategies including local and remote ischemic pre-, per-, and postconditioning have demonstrated consistent cardioprotective capacities in experimental models of acute ischemia-reperfusion injury. Their translation to the clinical scenario has been challenging. At present, the most promising mechanical protection strategy of the heart seems to be remote ischemic conditioning, which increases myocardial salvage beyond acute reperfusion therapy. An additional aspect that has gained recent focus is the potential of extended conditioning strategies to improve physical rehabilitation not only after an acute ischemia-reperfusion event such as acute myocardial infarction and cardiac surgery but also in patients with heart failure. Experimental and preliminary clinical evidence suggests that remote ischemic conditioning may modify cardiac remodeling and additionally enhance skeletal muscle strength therapy to prevent muscle waste, known as an inherent component of a postoperative period and in heart failure. Blood flow restriction exercise and enhanced external counterpulsation may represent cardioprotective corollaries. Combined with exercise, remote ischemic conditioning or, alternatively, blood flow restriction exercise may be of aid in optimizing physical rehabilitation in populations that are not able to perform exercise practice at intensity levels required to promote optimal outcomes.

Prevention of contrast-induced nephropathy by limb ischemic preconditioning: underlying mechanisms and clinical effects

Contrast-induced nephropathy (CIN) is an important complication following diagnostic radiographic imaging and interventional therapy. It results from administration of intravascular iodinated contrast media (CM) and is currently the third most common cause of hospital-acquired acute kidney injury. CIN is associated with increased morbidity, prolonged hospitalization, and higher mortality. Although the importance of CIN is widely appreciated, and its occurrence can be mitigated by the use of pre- and posthydration protocols and low osmolar instead of high osmolar iodine-containing CM, specific prophylactic therapy is lacking. Remote ischemic preconditioning (RIPC), induced through short cycles of ischemia-reperfusion applied to the limb, is an intriguing new strategy that has been shown to reduce myocardial infarction size in patients undergoing emergency percutaneous coronary intervention. Furthermore, multiple proof-of-principle clinical studies have suggested benefit in several other ischemia-reperfusion syndromes, including stroke. Perhaps somewhat surprisingly, RIPC also is emerging as a promising strategy for CIN prevention. In this review, we discuss current clinical and experimental developments regarding the biology of CIN, concentrating on the pathophysiology of CIN, and cellular and molecular mechanisms by which limb ischemic preconditioning may confer renal protection in clinical and experimental models of CIN.

Effects of preconditioned plasma collected during the late phase of remote ischaemic preconditioning on ventricular arrhythmias caused by myocardial ischaemia reperfusion in rats

Objective The administration of preconditioned plasma collected during the late phase of preconditioning has been shown to reduce myocardial infarct size. This study aimed to investigate if preconditioned plasma could attenuate ventricular arrhythmias in a rat model in vivo. Methods Eighty rats were randomized to eight groups (10 rats/group). Two groups provided preconditioned or non-preconditioned plasma 48 h after transient limb ischaemia or the control protocol. Six groups of ischaemia-reperfusion (IR) rats received normal saline, non-preconditioned plasma, or preconditioned plasma, respectively, 1 h (groups A1, A2, A3) or 24 h (groups B1, B2, B3) before undergoing myocardial IR. Electrocardiograms were monitored using a BIOPAC system, and the incidence and duration of ventricular tachycardia (VT) and ventricular fibrillation (VF) were analysed. Results No significant differences existed in the incidence and duration of VT or VF among groups A1-A3 or in the incidence and duration of VT among groups B1-B3. However, there was a significantly lower incidence and shorter duration of VF in group B3 rats than in group B1 rats. Conclusion Preconditioned plasma collected during the late phase of preconditioning can reduce the incidence and duration of VF compared with normal saline, suggesting its anti-arrhythmic potential.

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.

Ischaemic preconditioning - Current knowledge and potential future applications after 30 years of experience

Ischaemic preconditioning (IPC) phenomenon has been known for thirty years. During that time several studies showed that IPC provided by brief ischaemic and reperfusion episodes prior to longer ischaemia can bestow a protective effect to both preconditioned and also remote organs. IPC affecting remote organs is called remote ischaemic preconditioning. Initially, most IPC studies were focused on enhancing myocardial resistance to subsequent ischaemia and reperfusion injury. However, preconditioning was found to be a universal phenomenon and was observed in various organs and tissues including the heart, liver, brain, retina, kidney, skeletal muscles and intestine. Currently, there are a lot of simultaneous studies are underway aiming at finding out whether IPC can be helpful in protecting these organs. The mechanism of local and remote IPC is complex and not well known. Several triggers, intracellular pathways and effectors, humoral, neural and induced by genetic changes may be considered potential pathways in the protective activity of local and remote IPC. Local and remote IPC mechanism may potentially serve as heart protection during cardiac surgery and may limit the infarct size of the myocardium, can be a strategy for preventing the development of acute kidney injury development and liver damage during transplantation, may protect the brain against ischaemic injury. In addition, the method is safe, non-invasive, cheap and easily applicable. The main purpose of this review article is to present new advances which would help to understand the potential mechanism of IPC. It also discusses both its potential applications and utility in clinical settings.

Remote Ischemic Conditioning: The Commercial Market? CellAegis Perspective

Remote ischemic conditioning (RIC) is at a pivotal point in its evolution, both in terms of its adoption as a therapy and its viability commercially. The most usual way of inducing RIC, with a standard blood pressure cuff and a stopwatch, is time-consuming and potentially inaccurate and unsafe. Development of automated devices have facilitated large-scale randomized trials and will make clinical deployment of the technique more straightforward. Both the medical and commercial future of RIC will depend on the results of upcoming phase 3 pivotal trials.

Remote Ischemic Conditioning in Elective PCI?

This review examines the rationale for using remote ischemic conditioning (RIC) in elective percutaneous coronary intervention (PCI) to prevent procedure-related ischemia-reperfusion injury and justifies the importance of periprocedural biomarker elevation following elective PCI as a valid target for RIC. We review the evidence for the use of RIC as a treatment in this setting and document the salutary rules that must be followed to successfully translate RIC for clinical benefit.

The impact of a single episode of remote ischemic preconditioning on myocardial injury after elective percutaneous coronary intervention

Introduction

Myocardial injury after percutaneous coronary intervention (PCI) occurs in approximately 30% of procedures, and is related to worse prognosis. Effects of remote ischemic preconditioning (RIPC) on reperfusion injury have been investigated before, yielding conflicting results.

Aim

To assess the impact of a single episode of RIPC on myocardial injury after elective PCI.

Material and methods

One hundred and four patients undergoing elective PCI, with normal baseline cardiac troponin-I (cTn-I) values, were randomized to two groups. Two patients were excluded due to data loss, and 102 patients were analyzed. Five minutes of ischemic preconditioning was delivered just before the intervention to the preconditioning group, by inflating the blood pressure cuff up to 200 mm Hg on the non-dominant arm. Postprocedural 16^th hour cTn-I, ΔcTn-I (difference between the 16^th h and baseline cTn-I values) and the prevalence of type 4a myocardial infarction were compared between the two groups.

Results

Median cTn-I values after the procedure were compared. 16^th hour cTn-I was insignificantly lower in the preconditioning arm (0.026 μg/l vs. 0.045 μg/l, p = 0.186). The incidence of cTn-I elevation 5-fold above the upper reference limit (URL) (> 0.115 μg/l) was lower in the preconditioning group, but it was also not significant (21.6% vs. 11.8%, p = 0.184).

Conclusions

A single episode of RIPC before elective PCI demonstrated less troponin elevation but failed to show a significant effect.

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.

Repeat remote ischaemic pre-conditioning for improved cardiovascular function in humans: A systematic review

BACKGROUND

Single exposure to remote ischaemic pre-conditioning (RIPC) has been shown to be effective in reducing major adverse events during cardiac surgery. We evaluated the efficacy of repeated exposure RIPC to elicit improvements in cardiovascular function.

METHODS

A systematic search was conducted up until May 1st, 2015, using the following databases: EMBASE, PubMed (Medline), Web of Science and the Cochrane Central Registry of Controlled Trials (CENTRAL). Data was extracted and synthesized from published studies of repeat RIPC.

RESULTS

Data from seven studies showed evidence of improvements in vascular function and anti-hypertensive effects of systolic, diastolic and mean arterial blood pressure following repeat RIPC. Currently existing work justifies a systematic review but not data pooling of individual study data. Repeat RIPC has also produced evidence of improvements in endothelial dependent vasodilation, but not non-endothelial dependent vasodilation, cutaneous vascular conductance or cardiorespiratory fitness.

CONCLUSION

Repeated RIPC exposure has produced evidence of improvements in endothelial dependent vasodilation, ulcer healing and blood pressure but no benefit in non-endothelial dependent vasodilation, cutaneous vascular conductance or cardiorespiratory fitness. The optimal delivery of RIPC remains unclear, but at least 3 or preferably 4, 5 min exposures appears to be most beneficial, at least for reducing blood pressure. Aside from those undertaking cardiac surgery, other study populations with endothelial dysfunction may benefit from repeat exposure to RIPC.

Kinetics and Signal Activation Properties of Circulating Factor(s) From Healthy Volunteers Undergoing Remote Ischemic Pre-Conditioning

Although remote ischemic pre-conditioning (RIPC) reduced infarct size in animal experiments and proof-of-concept clinical trials, recent phase III trials failed to confirm cardioprotection during cardiac surgery. Here, we characterized the kinetic properties of humoral factors that are released after RIPC, as well as the signal transduction pathways that were responsible for cardioprotection in an ex vivo model of global ischemia reperfusion injury. Venous blood from 20 healthy volunteers was collected at baseline and 5 min, 30 min, 1 h, 6 h, and daily from 1 to 7 days after RIPC (3 × 5/5 min upper-limb ischemia/reperfusion). Plasma-dialysates (cut-off: 12 to 14 kDa; dilution: 1:20) were infused into Langendorff-perfused mouse hearts subjected to 20/120 min global ischemia/reperfusion. Infarct size and phosphorylation of signal transducer and activator of transcription (STAT)3, STAT5, extracellular-regulated kinase 1/2 and protein kinase B were determined. In a subgroup of plasma-dialysates, an inhibitor of STAT3 (Stattic) was used in mouse hearts. Perfusion with baseline-dialysate resulted in an infarct size of 39% of ventricular mass (interquartile range: 36% to 42%). Perfusion with dialysates obtained 5 min to 6 days after RIPC significantly reduced infarct size by ∼50% and increased STAT3 phosphorylation beyond that with baseline-dialysate. Inhibition of STAT3 abrogated these effects. These results suggest that RIPC induces the release of cardioprotective, dialyzable factor(s) within 5 min, and that circulate for up to 6 days. STAT3 is activated in murine myocardium by RIPC-induced human humoral factors and is causally involved in cardioprotection.

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Pre-clinical and early phase clinical studies with remote ischemic preconditioning (RIPC) appeared promising; however, RIPC was not effective in phase III clinical trials.

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To improve the translation of RIPC into clinical practice, the kinetic properties and functional effects of humoral factors released after RIPC in humans were characterized ex vivo.

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Venous blood from 20 healthy volunteers was collected at baseline and 5 min, 30 min, 1 h, 6 h and daily from 1 to 7 days after RIPC. Plasma dialysates were infused into Langendorff-perfused mouse hearts subjected to 20/120 min global ischemia/reperfusion.

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Perfusion with dialysates obtained 5 min to 6 days after RIPC significantly reduced infarct size by ∼50% when compared to perfusion with dialysates obtained at baseline prior to RIPC, and increased STAT3 phosphorylation beyond values obtained with baseline-dialysate.

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.

Remote ischemic conditioning

In remote ischemic conditioning (RIC), brief, reversible episodes of ischemia with reperfusion in one vascular bed, tissue, or organ confer a global protective phenotype and render remote tissues and organs resistant to ischemia/reperfusion injury. The peripheral stimulus can be chemical, mechanical, or electrical and involves activation of peripheral sensory nerves. The signal transfer to the heart or other organs is through neuronal and humoral communications. Protection can be transferred, even across species, with plasma-derived dialysate and involves nitric oxide, stromal derived factor-1α, microribonucleic acid-144, but also other, not yet identified factors. Intracardiac signal transduction involves: adenosine, bradykinin, cytokines, and chemokines, which activate specific receptors; intracellular kinases; and mitochondrial function. RIC by repeated brief inflation/deflation of a blood pressure cuff protects against endothelial dysfunction and myocardial injury in percutaneous coronary interventions, coronary artery bypass grafting, and reperfused acute myocardial infarction. RIC is safe and effective, noninvasive, easily feasible, and inexpensive.

Remote ischaemic conditioning in percutaneous coronary intervention: a meta-analysis of randomised trials

Introduction

It remains uncertain whether remote ischaemic conditioning (RIC) using cycles of limb ischaemia-reperfusion as a conditioning stimulus benefits patients undergoing percutaneous coronary intervention (PCI).

Aim

We performed a meta-analysis toassessthe effect of RIC in PCI.

Material and methods

The PubMed, EMBASE, Web of Science, and CENTRAL databases were searched for randomised controlled trials (RCTs) comparing RIC with controls. The treatment effects were measured as a pooled odds ratio (OR), standardised mean difference (SMD), and corresponding 95% confidence intervals (95% CIs) using random-effects models.

Results

Fourteen RCTs, including 2,301 patients, were analysed. Compared to the controls, RIC significantly reduced the cardiac enzyme levels (SMD = –0.21; 95% CI: –0.39 to –0.04; p = 0.015; heterogeneity test, I² = 75%), and incidence of PCI-related myocardial infarction (OR = 0.70; 95% CI, 0.51–0.98; p = 0.037). There was a trend toward an improvement in the complete ST-segment resolution rate with RIC (OR = 1.83; 95% CI: 0.99–3.40; p = 0.054). No significant difference could be detected between the two groups regarding the risk for acute kidney injury after PCI. Univariate meta-regression analysis suggested that the major source of significant heterogeneity was the PCI type (primary or non-emergent) for the myocardial enzyme levels (adjusted R² = 0.44). Subsequent subgroup analysis confirmed the results.

Conclusions

The present meta-analysis showed that RIC could confer cardioprotection for patients undergoing coronary stent implantation. Moreover, the decrease in the myocardial enzyme levels was more pronounced in the patients treated with primary PCI.