Simultaneous Inhibition of Thrombosis and Inflammation Is Beneficial in Treating Acute Myocardial Infarction

Myocardial ischemia reperfusion injury (IRI) in acute coronary syndromes is a condition in which ischemic/hypoxic injury to cells subtended by the occluded vessel continues despite successful resolution of the thrombotic obstruction. For decades, most efforts to attenuate IRI have focused on interdicting singular molecular targets or pathways, but none have successfully transitioned to clinical use. In this work, we investigate a nanoparticle-based therapeutic strategy for profound but local thrombin inhibition that may simultaneously mitigate both thrombosis and inflammatory signaling pathways to limit myocardial IRI. Perfluorocarbon nanoparticles (PFC NP) were covalently coupled with an irreversible thrombin inhibitor, PPACK (Phe[D]-Pro-Arg-Chloromethylketone), and delivered intravenously to animals in a single dose prior to ischemia reperfusion injury. Fluorescent microscopy of tissue sections and 19F magnetic resonance images of whole hearts ex vivo demonstrated abundant delivery of PFC NP to the area at risk. Echocardiography at 24 h after reperfusion demonstrated preserved ventricular structure and improved function. Treatment reduced thrombin deposition, suppressed endothelial activation, inhibited inflammasome signaling pathways, and limited microvascular injury and vascular pruning in infarct border zones. Accordingly, thrombin inhibition with an extraordinarily potent but locally acting agent suggested a critical role for thrombin and a promising therapeutic strategy in cardiac IRI.

Remote Ischemic Conditioning in Emergency Medicine-Clinical Frontiers and Research Opportunities

Time-critical acute ischemic conditions such as ST-elevation myocardial infarction and acute ischemic stroke are staples in Emergency Medicine practice. While timely reperfusion therapy is a priority, the resultant acute ischemia/reperfusion injury contributes to significant mortality and morbidity. Among therapeutics targeting ischemia/reperfusion injury (IRI), remote ischemic conditioning (RIC) has emerged as the most promising.RIC, which consists of repetitive inflation and deflation of a pneumatic cuff on a limb, was first demonstrated to have protective effect on IRI through various neural and humoral mechanisms. Its attractiveness stems from its simplicity, low-cost, safety, and efficacy, while at the same time it does not impede reperfusion treatment. There is now good evidence for RIC as an effective adjunct to reperfusion in ST-elevation myocardial infarction patients for improving clinical outcomes. For other applications such as acute ischemic stroke, subarachnoid hemorrhage, traumatic brain injury, cardiac arrest, and spinal injury, there is varying level of evidence.This review aims to describe the RIC phenomenon, briefly recount its historical development, and appraise the experimental and clinical evidence for RIC in selected emergency conditions. Finally, it describes the practical issues with RIC clinical application and research in Emergency Medicine.

Can exercise training enhance the repeated remote ischaemic preconditioning stimulus on peripheral and cerebrovascular function in high-risk individuals?

BACKGROUND

Repeated exposure to remote ischaemic preconditioning (rIPC; short bouts of non-lethal ischaemia) enhances peripheral vascular function within 1 week; whereas, longer periods of rIPC (~ 1 year) may improve cerebral perfusion. Increasing the 'dose' of rIPC may lead to superior effects. Given the similarities between exercise and rIPC, we examined whether adding exercise to the rIPC stimulus leads to greater adaptation in systemic vascular function.

METHODS

Nineteen individuals with increased risk for cardiovascular disease (CVD) were randomly allocated to either 8 weeks of rIPC (n = 9) or 8 weeks of rIPC + exercise (rIPC + Ex) (n = 10). rIPC was applied three times per week in both conditions, and exercise consisted of 50 min (70% heart rate max) of cycling 3 times per week. Peripheral endothelial function was assessed using flow-mediated dilation (FMD) before and after ischaemia-reperfusion (IR). Cerebrovascular function was assessed by dynamic cerebral autoregulation (dCA) and cerebrovascular reactivity (CVR), and cardio-respiratory fitness (VO_2peak) using a maximal aerobic capacity test.

RESULTS

FMD% increased by 1.6% (95% CI, 0.4, 2.8) following rIPC + Ex and by 0.3% (- 1.1, 1.5) in the only rIPC but this did not reach statistical significance (P = 0.65). Neither intervention evoked a change in dCA or in CVR (P > 0.05). VO_2peak increased by 2.8 ml/kg/min (1.7, 3.9) following the rIPC + Ex and by 0.1 ml/kg/min (- 1.0, 1.4) following the rIPC only intervention (P = 0.69).

CONCLUSION

Combining exercise with rIPC across an 8-week intervention does not lead to superior effects in cerebrovascular and peripheral vascular function compared to a repeated rIPC intervention in individuals at risk of CVD.