Two weeks of remote ischemic conditioning improves brachial artery flow mediated dilation in chronic stroke survivors

The potential mechanism and clinical application value of remote ischemic conditioning in stroke

Some studies have confirmed the neuroprotective effect of remote ischemic conditioning against stroke. Although numerous animal researches have shown that the neuroprotective effect of remote ischemic conditioning may be related to neuroinflammation, cellular immunity, apoptosis, and autophagy, the exact underlying molecular mechanisms are unclear. This review summarizes the current status of different types of remote ischemic conditioning methods in animal and clinical studies and analyzes their commonalities and differences in neuroprotective mechanisms and signaling pathways. Remote ischemic conditioning has emerged as a potential therapeutic approach for improving stroke-induced brain injury owing to its simplicity, non-invasiveness, safety, and patient tolerability. Different forms of remote ischemic conditioning exhibit distinct intervention patterns, timing, and application range. Mechanistically, remote ischemic conditioning can exert neuroprotective effects by activating the Notch1/phosphatidylinositol 3-kinase/Akt signaling pathway, improving cerebral perfusion, suppressing neuroinflammation, inhibiting cell apoptosis, activating autophagy, and promoting neural regeneration. While remote ischemic conditioning has shown potential in improving stroke outcomes, its full clinical translation has not yet been achieved.

Promoting Resiliency to Stress in the Vascular Endothelium

By 2050, roughly 60% of the population will have cardiovascular disease. While a substantial amount of data has been generated over the last few decades that has aided in our understanding of cardiovascular disease pathology, less is known about how to increase resiliency to cardiovascular risk factors that individuals are exposed to on a daily basis. The vascular endothelium is considered the first line of defence against circulating noxious stimuli and, when dysfunctional, is an early risk factor for the development of cardiovascular disease. A vast amount of data has been generated demonstrating how external stress impairs the vascular endothelium; however, there is a paucity of knowledge regarding how to amplify protective pathways and ward off stress and the development of disease, which is the focus of this review. Targeting known protective endothelial pathways may be feasible to increase resiliency to vascular stress. Leveraging stress to boost defence mechanisms within the vascular endothelium is also proposed and may help identify novel therapeutic targets to protect individuals from the stress of everyday life.

Effects of ischemic conditioning on microvascular reactivity to single passive limb movement in young adults: a pilot study

PURPOSE

Single passive limb movement (sPLM) of the lower extremity is a simple and clinically relevant measure of the microvascular vasodilatory response to movement. A promising stimulus to improve microvascular health is ischemic conditioning (IC). We examined whether a single session of IC could improve microvascular reactivity to sPLM in young adults.

METHODS

This was a blinded, crossover, randomized clinical trial. Participants were seated in an isokinetic dynamometer that passively moved the knee 90° at a frequency of 1 Hz while superficial femoral artery leg blood flow (LBF) was measured. The absolute and the relative peak changes in LBF were calculated as the difference from baseline. The time to peak was calculated from the start of sPLM to peak LBF. The total area under the curve (AUC) was the sum of LBF above baseline during the hyperemic response. For IC, the cuff was placed around the dominant thigh and repetitively inflated (225 mmHg) for 5 min, then deflated for 5 min (total 45 min). For sham IC, the cuff was inflated to 25 mmHg. The sPLM response was re-assessed ten minutes after IC.

RESULTS

Twelve individuals completed the study (age 27 ± 3 years, 50% female). When controlling for resting LBF, heart rate, and sex, there was an interaction effect for absolute and relative peak change in LBF (p ≤ 0.048) but not time to peak or total AUC (p ≥ 0.17).

CONCLUSION

We show an acute bout of IC may improve the peak vasodilatory response to sPLM, potentially due to "preconditioning" the microvasculature.

Ischemic Preconditioning Negatively Affects Thrombogenic Clotting Profile in Cerebral Small Vessel Occlusion Stroke Patients

Background

The study evaluated the effect of an acute and a 2-week daily repetitive ischemic preconditioning (IPC) on conduit artery vascular function and thrombogenic clotting profile, in patients with a recent ischemic stroke.

Methods

Fourteen patients, aged 71 ± 8 years, with a cerebral small vessel occlusion stroke were included in a randomized, controlled, open-label cross-over study. Treatment consisted of 2 weeks of daily IPC, four 5-min rounds of upper-arm occlusion, interspersed by 5 min rest periods. Control was without treatment. Brachial artery flow-mediated dilation (FMD) was determined at baseline and after the control and treatment periods. Before and after each period, the patients underwent an acute bout of IPC. Blood samples were obtained for thrombogenic clotting profile at baseline and after the acute IPC bout, both before and after the control and treatment periods.

Results

The period of daily IPC increased brachial artery diameter but did not influence FMD. Acutely, IPC was found to induce an increase in fractal dimension, indicating a denser clot microstructure, and a reduction in plasma levels of plasminogen activator inhibitor 1 (PAI-1). There was no effect of daily IPC on the basal thrombogenic clotting profile, or on the change in clotting profile induced by acute IPC.

Conclusions

Collectively, the data show that acute IPC leads to a prothrombotic clotting profile, despite antiplatelet therapy. Moreover, 2 weeks of daily treatment with IPC does not influence conduit artery vascular function or thrombogenicity in stroke patients.

Remote ischaemic conditioning for neurological disorders-a systematic review and narrative synthesis

INTRODUCTION

Remote ischaemic conditioning (RIC) refers to the use of controlled transient ischemic and reperfusion cycles, commonly of the upper or lower limb, to mitigate cellular damage from ischaemic injury. Preclinical studies demonstrate that RIC may have a neuroprotective effect and therefore could represent a novel therapeutic option in the management of neurological disorders. The aim of this review is to comprehensively describe the current clinical evidence of RIC in neurological disorders.

METHODS

A computerised search of EMBASE and OVID MEDLINE was conducted from 2002 to October 2023 for randomised controlled trials (RCTs) investigating RIC in neurological diseases.

RESULTS

A total of 46 different RCTs in 12 different neurological disorders (n = 7544) were included in the analysis. Conditions included acute ischaemic stroke, symptomatic intracranial stenosis and vascular cognitive impairment. The most commonly used RIC protocol parameters in the selected studies were as follows: cuff pressure at 200 mmHg (27 trials), 5-min cycle length (42 trials), 5 cycles of ischaemia and reperfusion (24 trials) and the application to the upper limb unilaterally (23 trials).

CONCLUSIONS

The comprehensive analysis of the included studies reveals promising results regarding the safety and therapeutic effect of RIC as an option for managing neurological diseases. Particularly, the strongest evidence supports its potential use in chronic stroke patients and vascular cognitive impairment. The neuroprotective effects of RIC, as demonstrated in preclinical studies, suggest that this therapeutic approach could extend its benefits to various other diseases affecting the nervous system. However, to establish the efficacy of RIC across different neurological disorders, further trials with larger sample sizes and more diverse patient populations are warranted. Upcoming trials are expected to provide valuable evidence that will not only confirm the efficacy of RIC in neurological disease management but also help identify the most optimal RIC regimen for specific conditions.

Blood flow modulation to improve motor and neurophysiological outcomes in individuals with stroke: a scoping review

Ischemic Conditioning (IC) is a procedure involving brief periods of occlusion followed by reperfusion in stationary limbs. Blood Flow Restriction with Exercise (BFR-E) is a technique comprising blood flow restriction during aerobic or resistance exercise. Both IC and BFR-E are Blood Flow Modulation (BFM) strategies that have shown promise across various health domains and are clinically relevant for stroke rehabilitation. Despite their potential benefits, our knowledge on the application and efficacy of either intervention in stroke is limited. This scoping review aims to synthesize the existing literature on the impact of IC and BFR-E on motor and neurophysiological outcomes in individuals post-stroke. Evidence from five studies displayed enhancements in paretic leg strength, gait speed, and paretic leg fatiguability after IC. Additionally, BFR-E led to improvements in clinical performance, gait parameters, and serum lactate levels. While trends toward motor function improvement were observed post-intervention, statistically significant differences were limited. Neurophysiological changes showed inconclusive results. Our review suggests that IC and BFR-E are promising clinical approaches in stroke, however high-quality studies focusing on neurophysiological mechanisms are required to establish the efficacy and underlying mechanisms of both in stroke. Recommendations regarding future directions and clinical utility are provided.

The Impact of Remote Ischemic Preconditioning on Inflammation Markers in Patients Undergoing Coronary Artery Bypass Grafting

Background

This study aimed to investigate if remote ischemic preconditioning reduces the inflammatory process on patients undergoing coronary artery bypass grafting (CABG).

Methods

We conducted a case-control study involving 80 patients, half of whom underwent ischemic preconditioning for severe coronary artery disease (CAD) and subsequently underwent CABG. We assessed interleukin (IL)-1 and IL-6 levels using the enzyme-linked immunosorbent assay (ELISA) method, high-sensitivity troponin I (hsTnI) using chemiluminescent immunoassay (CLIA), and C-reactive protein (CRP) using the turbidimetric method at three key time points: before surgery (visit 1 or V1), immediately postoperatively (visit 2 or V2), and 1 week postoperatively (visit 3 or V3) in all subjects.

Results

Ischemic preconditioned patients showed a significant decrease in proinflammatory markers (IL-1, IL-6) but not in CRP or hsTnI.

Conclusions

This study demonstrated that remote ischemic preconditioning significantly reduced the levels of specific proinflammatory markers (IL-1 and IL-6), which may suggest general systemic protection. However, it did not demonstrate cardioprotection per se, as evidenced by the absence of a statistically significant decrease in hsTnI level.

Noninvasive estimation of skeletal muscle oxygen consumption rate and microvascular reactivity in chronic stroke survivors using near-infrared spectroscopy

Understanding post-stroke changes in skeletal muscle oxidative metabolism and microvascular reactivity could help create therapeutic targets that optimize rehabilitative interventions. Due to disuse atrophy, we hypothesized that basal muscle oxygen consumption rate and microvascular endothelial function would be impaired in the tibialis anterior (TA) muscle of the affected leg of chronic stroke survivors compared with the nonaffected leg and versus matched controls. Fifteen chronic stroke survivors (10 females) and 15 matched controls (9 females) completed this study. A near-infrared spectroscopy oximeter measured tissue oxygen saturation (StO2) of the TA in both legs of stroke survivors and the dominant leg of controls. A cuff was placed around the thigh and inflated to 225 mmHg for 5 min while StO2 was continuously measured. The rate of change in StO2 was calculated during cuff occlusion and immediately post-cuff release. The rate of oxygen desaturation was similar between the legs of the stroke survivors (paretic -0.12 ± 0.04%·s-1 vs. nonparetic -0.16 ± 011%·s-1; P = 0.49), but the paretic leg had a reduced desaturation rate versus controls (-0.25 ± 0.18%·s-1; P = 0.007 vs. paretic leg). After cuff release, there was a greater oxygen resaturation rate in the nonparetic leg compared with the paretic leg (3.13 ± 2.08%·s-1 vs. 1.60 ± 1.11%·s-1, respectively; P = 0.01). The control leg had a similar resaturation rate versus the nonparetic leg (control = 3.41 ± 1.79%·s-1; P = 0.69) but was greater than the paretic leg (P = 0.003). The TA in the paretic leg had an impaired muscle oxygen consumption rate and reduced microvascular endothelial function compared with controls.NEW & NOTEWORTHY Secondary consequences of stroke are not well described. In this study, we show that basal muscle oxidative consumption and microvascular endothelial function are reduced in the paretic tibialis anterior muscle of chronic stroke survivors compared with matched controls using near-infrared spectroscopy and the vascular occlusion technique. There was a moderately strong correlation between microvascular endothelial function and paretic leg strength.

Peripheral vascular function in stroke: systematic review and meta-analysis

Peripheral vascular dysfunction, measured as flow-mediated dilation (FMD), is present across all phases of stroke recovery and elevates the risk for recurrent cardiovascular events. The objective of this systematic review and meta-analysis was to characterize baseline FMD in individuals' poststroke, with consideration for each phase of stroke recovery. Three databases (PubMed, CINAHL, and Embase) were searched between January 1, 2000 and October 12, 2023 for studies that examined baseline FMD in stroke. Three reviewers conducted abstract and full-text screening, data extraction, and quality assessment. A random effects model was used to estimate FMD across studies. Meta-regression was used to examine the impact of age and time since stroke (acute, subacute, chronic) on FMD. Twenty-eight studies with ischemic and hemorrhagic stroke were included. Descriptive statistics for the demographics and FMD values of each study are presented. For the meta-analysis, average estimate FMD was 3.9% (95% CI: 2.5-5.3%). We report a large amount of heterogeneity (Cochrane's Q P value <0.001, and I2 = 99.6%). Differences in average age and the time poststroke between studies were not significantly associated with differences in FMD values. Despite the large heterogeneity for FMD values across studies, our primary finding suggests that FMD remains impaired across all phases of stroke.NEW & NOTEWORTHY This systematic review and meta-analysis offers invaluable insight into poststroke vascular function. Despite the inherent heterogeneity among the 28 studies analyzed, we report that peripheral vascular dysfunction, as quantified by flow-mediated dilation, exists across all stages of stroke recovery. This finding underscores the importance for interventions that focus on improving vascular health and secondary stroke prevention.

Remote ischemic conditioning for stroke: A critical systematic review

Remote ischemic conditioning (RIC) is the application of brief periods of ischemia to an organ or tissue with the aim of inducing protection from ischemia in a distant organ. It was first developed as a cardioprotective strategy but has been increasingly investigated as a neuroprotective intervention. The mechanisms by which RIC achieves neuroprotection are incompletely understood. Preclinical studies focus on the hypothesis that RIC can protect the brain from ischemia reperfusion (IR) injury following the restoration of blood flow after occlusion of a large cerebral artery. However, increasingly, a role of chronic RIC (CRIC) is being investigated as a means of promoting recovery following an ischemic insult to the brain. The recent publication of two large, randomized control trials has provided promise that RIC could improve functional outcomes after acute ischemic stroke, and that there may be a role for CRIC in the prevention of recurrent stroke. Although less developed, there is also proof-of-concept to suggest that RIC may be used to reduce vasospasm after subarachnoid hemorrhage or improve cognitive outcomes in vascular dementia. As a cheap, well-tolerated and almost universally applicable intervention, the motivation for investigating possible benefit of RIC in patients with cerebrovascular disease is great. In this review, we shall review the current evidence for RIC as applied to cerebrovascular disease.

Remote ischaemic preconditioning - translating cardiovascular benefits to humans

Remote ischaemic preconditioning (RIPC), induced by intermittent periods of limb ischaemia and reperfusion, confers cardiac and vascular protection from subsequent ischaemia–reperfusion (IR) injury. Early animal studies reliably demonstrate that RIPC attenuated infarct size and preserved cardiac tissue. However, translating these adaptations to clinical practice in humans has been challenging. Large clinical studies have found inconsistent results with respect to RIPC eliciting IR injury protection or improving clinical outcomes. Follow‐up studies have implicated several factors that potentially affect the efficacy of RIPC in humans such as age, fitness, frequency, disease state and interactions with medications. Thus, realizing the clinical potential for RIPC may require a human experimental model where confounding factors are more effectively controlled and underlying mechanisms can be further elucidated. In this review, we highlight recent experimental findings in the peripheral circulation that have added valuable insight on the mechanisms and clinical benefit of RIPC in humans. Central to this discussion is the critical role of timing (i.e. immediate vs. delayed effects following a single bout of RIPC) and the frequency of RIPC. Limited evidence in humans has demonstrated that repeated bouts of RIPC over several days uniquely improves vascular function beyond that observed with a single bout alone. Since changes in resistance vessel and microvascular function often precede symptoms and diagnosis of cardiovascular disease, repeated bouts of RIPC may be promising as a preclinical intervention to prevent or delay cardiovascular disease progression.

Chronic Limb Remote Ischemic Conditioning may have an Antihypertensive Effect in Patients with Hypertension

Hypertension is the leading preventable risk factor for all-cause morbidity and mortality worldwide. Despite antihypertensive medications have been available for decades, a big challenge we are facing is to increase the blood pressure (BP) control rate among the population. Therefore, it is necessary to search for new antihypertensive means to reduce the burden of disease caused by hypertension. Limb remote ischemic conditioning (LRIC) can trigger endogenous protective effects through transient and repeated ischemia on the limb to protect specific organs and tissues including the brain, heart, and kidney. The mechanisms of LRIC involve the regulation of the autonomic nervous system, releasing humoral factors, improvement of vascular endothelial function, and modulation of immune/inflammatory responses. These underlying mechanisms of LRIC may restrain the pathogenesis of hypertension through multiple pathways theoretically, leading to a potential decline in BP. Several existing studies have explored the impact of LRIC on BP, however, controversial findings were reported. To explore the potential antihypertensive effect of LRIC and the underlying mechanisms, we systematically reviewed the relevant articles to provide an insight into the novel therapy of hypertension.

Therapeutic Potential of Remote Ischemic Conditioning in Vascular Cognitive Impairment

Vascular cognitive impairment (VCI) is a heterogeneous disease caused by a variety of cerebrovascular diseases. Patients with VCI often present with slower cognitive processing speed and poor executive function, which affects their independence in daily life, thus increasing social burden. Remote ischemic conditioning (RIC) is a non-invasive and efficient intervention that triggers endogenous protective mechanisms to generate neuroprotection. Over the past decades, evidence from basic and clinical research has shown that RIC is promising for the treatment of VCI. To further our understanding of RIC and improve the management of VCI, we summarize the evidence on the therapeutic potential of RIC in relation to the risk factors and pathobiologies of VCI, including reducing the risk of recurrent stroke, decreasing high blood pressure, improving cerebral blood flow, restoring white matter integrity, protecting the neurovascular unit, attenuating oxidative stress, and inhibiting the inflammatory response.