Aspirin Blocks the Infarct-Size Limiting Effect of Ischemic Postconditioning in the Rat

Aspirin loading and coronary no-reflow after percutaneous coronary intervention in patients with acute myocardial infarction

BACKGROUND

The association of aspirin loading with the risk of coronary no-reflow (CNR) after percutaneous coronary intervention (PCI) in patients with acute myocardial infarction (AMI) has not been investigated. We assessed the association of aspirin loading before PCI with CNR in patients with AMI.

MATERIALS AND METHODS

This study included 3100 patients with AMI undergoing PCI. Of them, 2812 patients received aspirin loading (a single oral [or chewed] or intravenous dose of 150-300 mg) and 288 patients did not receive aspirin loading before PCI. The primary endpoint was CNR, defined as Thrombolysis in Myocardial Infarction blood flow grade of <3 after the PCI.

RESULTS

CNR occurred in 130 patients: 127 patients in the group with aspirin loading and 3 patients in the group without aspirin loading before PCI (4.5% vs. 1.0%; odds ratio [OR] = 4.50, 95% confidence interval, [1.42-14.21], p = 0.005). After adjustment, the association between aspirin loading and CNR was significant (adjusted OR = 4.49 [1.56-12.92]; p < 0.001). There was no aspirin loading-by-P2Y12 inhibitor (ticagrelor or prasugrel) interaction (pint  = 0.465) or aspirin loading-by-chronic aspirin therapy on admission (pint  = 0.977) interaction with respect to the occurrence of CNR after PCI. Chronic low-dose aspirin therapy on admission was not independently associated with higher risk of CNR after PCI (adjusted OR = 1.06 [0.65-1.72]; p = 0.824).

CONCLUSION

In patients with AMI undergoing PCI, aspirin loading before the PCI procedure at the guideline-recommended doses was associated with higher odds of developing CNR. However, due to the limited number of events, the findings should be considered as hypothesis generating.

The Infarct-Limiting Effect of Remote Ischemic Conditioning in Rats Is Not Affected by Aspirin

PURPOSE

Remote ischemic conditioning (RIC) has been shown to be a powerful cardioprotective therapy in animal models. However, a protective effect in patients presenting with acute myocardial infarction has failed to be confirmed. A recent pre-clinical study reported that aspirin which is routinely given to patients undergoing reperfusion therapy blocked the infarct-limiting effect of ischemic postconditioning. The present study was designed to test whether aspirin could also be blocking the infarct-limiting effect of RIC.

METHODS

This was investigated in vivo using male Sprague Dawley rats (n = 5 to 6 per group) subjected to either 30 min of regional myocardial ischemia, followed by 120-min reperfusion, or additionally to a RIC protocol initiated after 20-min myocardial ischemia. The RIC protocol included four cycles of 5-min hind limb ischemia interspersed with 5-min reperfusion. Intravenous aspirin (30 mg/kg) or vehicle (saline) was administered after 15-min myocardial ischemia.

RESULTS

RIC significantly reduced infarct size (IS) normalized to the area at risk, by 47%. Aspirin administration did not affect IS nor did it attenuate the infarct-limiting effect of RIC.

CONCLUSION

Aspirin administration in the setting of myocardial infarction is not likely to interfere with the cardioprotective effect of RIC.

Platelet-Mediated Transfer of Cardioprotection by Remote Ischemic Conditioning and Its Abrogation by Aspirin But Not by Ticagrelor

PURPOSE

The role of platelets during myocardial ischemia/reperfusion (I/R) is ambivalent. They contribute to injury but also to cardioprotection. Repeated blood flow restriction and reperfusion in a tissue/organ remote from the heart (remote ischemic conditioning, RIC) reduce myocardial I/R injury and attenuate platelet activation. Whether or not platelets mediate RIC's cardioprotective signal is currently unclear.

METHODS AND RESULTS

Venous blood from healthy volunteers (without or with pretreatment of 500/1000 mg aspirin or 180 mg ticagrelor orally, 2-3 h before the study, n = 18 each) was collected before and after RIC (3 × 5 min blood pressure cuff inflation at 200 mmHg on the left upper arm/5 min deflation). Washed platelets were isolated. Platelet-poor plasma was used to prepare plasma-dialysates. Platelets (25 × 103/µL) or plasma-dialysates (1:10) prepared before and after RIC from untreated versus aspirin- or ticagrelor-pretreated volunteers, respectively, were infused into isolated buffer-perfused rat hearts. Hearts were subjected to global 30 min/120 min I/R. Infarct size was stained. Infarct size was less with infusion of platelets/plasma-dialysate after RIC (18 ± 7%/23 ± 9% of ventricular mass) than with platelets/plasma-dialysate before RIC (34 ± 7%/33 ± 8%). Aspirin pretreatment abrogated the transfer of RIC's cardioprotection by platelets (after/before RIC, 34 ± 7%/33 ± 7%) but only attenuated that by plasma-dialysate (after/before RIC, 26 ± 8%/32 ± 5%). Ticagrelor pretreatment induced an in vivo formation of cardioprotective factor(s) per se (platelets/plasma-dialysate before RIC, 26 ± 7%/26 ± 7%) but did not impact on RIC's cardioprotection by platelets/plasma-dialysate (20 ± 7%/21 ± 5%).

CONCLUSION

Platelets serve as carriers for RIC's cardioprotective signal through an aspirin-sensitive and thus cyclooxygenase-dependent mechanism. The P2Y12 inhibitor ticagrelor per se induces a humoral cardioprotective signal.

Lethal Caspase-1/4-Dependent Injury Occurs in the First Minutes of Coronary Reperfusion and Requires Calpain Activity

To study the relationship between caspase-1/4 and reperfusion injury, we measured infarct size (IS) in isolated mouse hearts undergoing 50 min global ischemia/2 h reperfusion. Starting VRT-043198 (VRT) at reperfusion halved IS. The pan-caspase inhibitor emricasan duplicated VRT's protection. IS in caspase-1/4-knockout hearts was similarly reduced, supporting the hypothesis that caspase-1/4 was VRT's only protective target. NLRC4 inflammasomes activate caspase-1. NLRC4 knockout hearts were not protected, eliminating NLRC4 as caspase-1/4's activator. The amount of protection that could be achieved by only suppressing caspase-1/4 activity was limited. In wild-type (WT) hearts, ischemic preconditioning (IPC) was as protective as caspase-1/4 inhibitors. Combining IPC and emricasan in these hearts or preconditioning caspase-1/4-knockout hearts produced an additive IS reduction, indicating that more protection could be achieved by combining treatments. We determined when caspase-1/4 exerted its lethal injury. Starting VRT after 10 min of reperfusion in WT hearts was no longer protective, revealing that caspase-1/4 inflicted its injury within the first 10 min of reperfusion. Ca⁺⁺ influx at reperfusion might activate caspase-1/4. We tested whether Ca⁺⁺-dependent soluble adenylyl cyclase (AC10) could be responsible. However, IS in AC10^-/- hearts was not different from that in WT control hearts. Ca⁺⁺-activated calpain has been implicated in reperfusion injury. Calpain could be releasing actin-bound procaspase-1 in cardiomyocytes, which would explain why caspase-1/4-related injury is confined to early reperfusion. The calpain inhibitor calpeptin duplicated emricasan's protection. Unlike IPC, adding calpain to emricasan offered no additional protection, suggesting that caspase-1/4 and calpain may share the same protective target.

Interaction of Cardiovascular Nonmodifiable Risk Factors, Comorbidities and Comedications With Ischemia/Reperfusion Injury and Cardioprotection by Pharmacological Treatments and Ischemic Conditioning

Preconditioning, postconditioning, and remote conditioning of the myocardium enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and the potential to provide novel therapeutic paradigms for cardioprotection. While many signaling pathways leading to endogenous cardioprotection have been elucidated in experimental studies over the past 30 years, no cardioprotective drug is on the market yet for that indication. One likely major reason for this failure to translate cardioprotection into patient benefit is the lack of rigorous and systematic preclinical evaluation of promising cardioprotective therapies prior to their clinical evaluation, since ischemic heart disease in humans is a complex disorder caused by or associated with cardiovascular risk factors and comorbidities. These risk factors and comorbidities induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury and responses to cardioprotective interventions. Moreover, some of the medications used to treat these comorbidities may impact on cardioprotection by again modifying cellular signaling pathways. The aim of this article is to review the recent evidence that cardiovascular risk factors as well as comorbidities and their medications may modify the response to cardioprotective interventions. We emphasize the critical need for taking into account the presence of cardiovascular risk factors as well as comorbidities and their 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 comorbidities. SIGNIFICANCE STATEMENT: Ischemic heart disease is a major cause of mortality; however, there are still no cardioprotective drugs on the market. Most studies on cardioprotection have been undertaken in animal models of ischemia/reperfusion in the absence of comorbidities; however, ischemic heart disease develops with other systemic disorders (e.g., hypertension, hyperlipidemia, diabetes, atherosclerosis). Here we focus on the preclinical and clinical evidence showing how these comorbidities and their routine medications affect ischemia/reperfusion injury and interfere with cardioprotective strategies.

Do We Really Need Aspirin Loading for STEMI?

Aspirin loading (chewable or intravenous) as soon as possible after presentation is a class I recommendation by current ST elevation myocardial infarction (STEMI) guidelines. Earlier achievement of therapeutic antiplatelet effects by aspirin loading has long been considered the standard of care. However, the effects of the loading dose of aspirin (alone or in addition to a chronic maintenance oral dose) have not been studied. A large proportion of myocardial cell death occurs upon and after reperfusion (reperfusion injury). Numerous agents and interventions have been shown to limit infarct size in animal models when administered before or immediately after reperfusion. However, these interventions have predominantly failed to show significant protection in clinical studies. In the current review, we raise the hypothesis that aspirin loading may be the culprit. Data obtained from animal models consistently show that statins, ticagrelor, opiates, and ischemic postconditioning limit myocardial infarct size. In most of these studies, aspirin was not administered. However, when aspirin was administered before reperfusion (as is the case in the majority of studies enrolling STEMI patients), the protective effects of statin, ticagrelor, morphine, and ischemic postconditioning were attenuated, which can be plausibly attributable to aspirin loading. We therefore suggest studying the effects of aspirin loading before reperfusion on the infarct size limiting effects of statins, ticagrelor, morphine, and/ or postconditioning in large animal models using long reperfusion periods (at least 24 h). If indeed aspirin attenuates the protective effects, clinical trials should be conducted comparing aspirin loading to alternative antiplatelet regimens without aspirin loading in patients with STEMI undergoing primary percutaneous coronary intervention.

Direct Ischemic Postconditioning After Carotid Endarterectomy in the Prevention of Postoperative Cerebral Ischemic Complications—Observational Case–Control Study

Introduction:

Ischemic postconditioning (IPCT) represents one of the several therapeutic strategies to attenuate ischemic reperfusion injury (IR) after carotid endarterectomy (CEA). We here present the first in-human study of IPCT in carotid surgery.

Methods:

The study represents an observational case-control study, with the data collected in our Institution carotid database. From December 2015 to December 2020, a total of 300 patients were included in our study; IPCT group consisted of 148 patients in whom ischemic postconditioning was performed while control group consisted of 152 patients in whom IPCT was not performed. Indications for IPCT technique were: severe unilateral internal carotid artery (ICA) stenosis (>90%), severe bilateral ICA stenosis (>80%), severe ICA stenosis (>80%) with contralateral ICA occlusion and ICA subocclusion. IPCT was performed by applying 6 cycles of 30 sec reperfusion (declamping of ICA)/30 sec ischemia (clamping of ICA) after finishing the procedure and initial declamping. Two groups of patients were compared in terms of occurrence of intrahospital and early postoperative stroke, TIA (transient ischemic attack) and neurologic morbidity.

Results:

Cumulative incidence of intrahospital postoperative stroke or TIA was significantly higher in the control group (5.3% vs 0.7%, P = .036). According to carotid plaque characteristics, patients in the IPCT group had significantly more frequent presence of heterogenous plaque, as well as ulcerated plaque, which was associated with the absence of postoperative stroke and significantly lower cumulative rate of TIA/stroke when compared to the control group (43.9% vs 8% and 47.3% vs 1.5%). During the follow-up period of 1 month after the surgery, there were no cases of stroke, TIA and deaths due to neurological causes in both groups of patients.

Conclusion:

Our results showed that IPCT significantly reduced the incidence of postoperative cerebral ischemic complications after CEA in high-risk patients for IR injury when compared to the control group.