Impact of mild hypothermia on platelet responsiveness to aspirin and clopidogrel: an in vitro pharmacodynamic investigation

Comparison of Clopidogrel Versus Ticagrelor for Percutaneous Coronary Intervention (PCI) Patients Managed with Therapeutic Hypothermia: A Systematic Review and Meta-Analysis

Various antiplatelet drugs, such as clopidogrel and ticagrelor, are available on the market for use after percutaneous coronary intervention (PCI). However, the efficacy of such drugs in patients being managed with therapeutic hypothermia (TH) has always been debated. In light of this controversy, this systematic review and meta-analysis was performed to enhance existing literature. Various databases were searched for potentially relevant studies from inception to April 2023, including PubMed, Cochrane Library, and Scopus. The risk of bias was assessed using the Newcastle-Ottawa scale for cohort studies and the Cochrane risk of bias tool for randomized controlled trials. Outcomes of interest included risk of bleeding, stent thrombosis, and all-cause mortality. Five studies were shortlisted for inclusion into the meta-analysis, featuring a total of 245 patients receiving either clopidogrel or ticagrelor. Overall, no significant differences were noted when the use of clopidogrel and ticagrelor was compared in PCI patients being managed with TH. To the best of our knowledge, this is the most comprehensive meta-analysis comparing the outcomes of clopidogrel and ticagrelor in PCI patients being managed with TH. Despite existing studies claiming an altered efficacy of clopidogrel in such conditions, our meta-analytic findings could not prove this relationship. Due to the limited sample size, further comprehensive and randomized studies are encouraged to arrive at a robust conclusion.

Balancing thrombosis and bleeding after out-of-hospital cardiac arrest related to acute coronary syndrome: A literature review

Balance between thrombosis and bleeding is now well recognized in patients treated for acute coronary syndrome, with impact on short- and long-term prognosis, including survival. Recent data suggest that patients who are resuscitated after out-of-hospital cardiac arrest related to myocardial infarction are at an even higher risk of bleeding and thrombosis than those with uncomplicated acute coronary syndrome. Delayed enteral absorption of medication due to induced hypothermia and systemic inflammation increases thrombosis risk, whereas transfemoral access site, cardiopulmonary resuscitation manoeuvres and mechanical circulatory support devices increase bleeding risk. In addition, post-resuscitation syndrome and renal or hepatic impairment are potential risk factors for both bleeding and thrombotic complications. There are currently no randomized controlled trials comparing various P₂Y₁₂ inhibitor and/or anticoagulation strategies in the setting of out-of-hospital cardiac arrest, and current practice is largely derived from management of patients with uncomplicated acute coronary syndrome. The aim of this review is therefore to describe the bleeding and thrombosis risk factors in this specific population, and to review recent data on antithrombotic drugs in this patient subset.

Effect of hypothermia on haemostasis and bleeding risk: a narrative review

It must be remembered that clinically important haemostasis occurs in vivo and not in a tube, and that variables such as the number of bleeding events and bleeding volume are more robust measures of bleeding risk than the results of analyses.

In this narrative review, we highlight trauma, surgery, and mild induced hypothermia as three clinically important situations in which the effects of hypothermia on haemostasis are important. In observational studies of trauma, hypothermia (body temperature <35°C) has demonstrated an association with mortality and morbidity, perhaps owing to its effect on haemostatic functions. Randomised trials have shown that hypothermia causes increased bleeding during surgery. Although causality between hypothermia and bleeding risk has not been well established, there is a clear association between hypothermia and negative outcomes in connection with trauma, surgery, and accidental hypothermia; thus, it is crucial to rewarm patients in these clinical situations without delay. Mild induced hypothermia to ≥33°C for 24 hours does not seem to be associated with either decreased total haemostasis or increased bleeding risk.

A systematic review of randomized trials comparing double versus triple antithrombotic therapy in patients with atrial fibrillation undergoing percutaneous coronary intervention

BACKGROUND

Prior randomized controlled trials (RCT) evaluating the optimal antithrombotic therapies for patients with atrial fibrillation (AF) undergoing percutaneous coronary intervention (PCI) have not been powered to evaluate ischemic outcomes. We compared double therapy with oral anticoagulation (OAC) and a P2Y12 inhibitor to triple therapy with an OAC + dual antiplatelet therapy in patients with AF requiring PCI.

METHODS

Using PRISMA guidelines, we searched for RCTs including patients with AF as an indication for OAC and undergoing PCI or medical management of acute coronary syndrome. The results were pooled using fixed-effects and random-effects models to estimate the overall effect of double therapy versus triple therapy on ischemic and bleeding outcomes.

RESULTS

We identified four RCTs, comprising 10,238 patients (5,498 double therapy, 4,740 triple therapy). Trial-reported major adverse cardiovascular events were similar between double therapy and triple therapy (fixed effect model OR 1.09, 95% CI 0.94-1.26). However, stent thrombosis (61/5,496 double therapy vs. 33/4738 triple therapy; fixed effect model OR 1.57, 95% CI 1.02-2.40; number needed to treat with triple therapy = 242) favored triple therapy. Bleeding outcomes were less frequent with double therapy (746/5470 vs. 950/4710; fixed effect model OR 0.59, 95% CI 0.53-0.65; number needed to harm with triple therapy = 16), but with significant heterogeneity (Q = 8.33, p = .04; I² = 64%), as were intracranial hemorrhages (19/5470 vs. 30/4710; fixed effect model OR 0.54, 95% CI 0.31-0.96).

CONCLUSIONS

Double therapy in patients with AF requiring OAC following PCI or Acute coronary syndrome has a significantly better safety profile than triple therapy but may be associated with a modest increased risk of stent thrombosis.

Impact of mild therapeutic hypothermia on bioavailability of ticagrelor in patients with acute myocardial infarction after out-of-hospital cardiac arrest

BACKGROUND

Out-of-hospital cardiac arrest (OHCA) frequently occurs in the early phase of acute myocardial infarction (MI). Survivors require percutaneous coronary intervention (PCI) with concomitant dual antiplatelet therapy. Target temperature management, including mild therapeutic hypothermia (MTH), should be applied in comatose patients after resuscitation. However, an increased risk of stent thrombosis in patients undergoing hypothermia is observed. The aim of this study was to assess the impact of MTH on pharmacokinetics of ticagrelor in cardiac arrest survivors with MI treated with MTH and PCI.

METHODS

In a prospective, observational, single-center study pharmacokinetics of ticagrelor were evaluated in 41 MI patients, including 11 patients after OHCA undergoing MTH (MTH group) and 30 MI patients without OHCA and MTH (no-MTH group). Blood samples were drawn before administration of a 180 mg ticagrelor loading dose, and 30 min, 1, 2, 4, 6, 12, and 24 h after the loading dose.

RESULTS

In patients treated with MTH total exposure to ticagrelor during the first 12 h after the loading dose and maximal plasma concentration of ticagrelor were significantly lower than in the no-MTH group (AUC(0-12): 3403 ± 2879 vs. 8746 ± 5596 ng·h/mL, difference: 61%, p = 0.01; Cmax: 475 ± 353 vs. 1568 ± 784 ng/mL, p = 0.0002). Time to achieve maximal ticagrelor plasma concentration was also delayed in the MTH group (tmax for ticagrelor: 12 [6-24] vs. 4 [2-12] h, p = 0.01).

CONCLUSIONS

Bioavailability of ticagrelor was substantially decreased and delayed in MI patients treated with MTH after OHCA.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02611934.

High and low on-treatment platelet reactivity to P2Y12 inhibitors in a contemporary cohort of acute coronary syndrome patients undergoing percutaneous coronary intervention

INTRODUCTION

There is compelling evidence supporting the association between high on-treatment platelet reactivity (HPR) and low on-treatment platelet reactivity (LPR) to clopidogrel with atherothrombotic and bleeding events, respectively. However, it is uncertain if current cutoff values should be used in prasugrel- or ticagrelor-treated subjects. The objective of this analysis was to evaluate the pharmacodynamic (PD) efficacy of P2Y₁₂ antagonists in a contemporary real-world population.

MATERIALS AND METHODS

This PD study included 988 patients with acute coronary syndromes (ACS) undergoing percutaneous coronary intervention (PCI) and receiving dual therapy with aspirin and a P2Y₁₂ inhibitor (clopidogrel, prasugrel or ticagrelor). Platelet function was assessed at day 1 and day 30 post-PCI by VerifyNow P2Y12 assay, multiple electrode aggregometry and vasodilator-stimulated phosphoprotein (VASP) assay.

RESULTS

Clopidogrel-treated patients (n = 324) had greater platelet reactivity than those receiving ticagrelor (n = 469) or prasugrel (n = 195) at both time points (p < 0.001 for all comparisons). No difference between ticagrelor and prasugrel was observed at day 1 with the VerifyNow P2Y12 assay (51.5 ± 2.8 vs. 42.7 ± 3.5 PRUs; p = 0.298), whereas ticagrelor achieved greater platelet inhibition at day 30 (48.1 ± 2.5 vs. 89.2 ± 4.2 PRUs; p < 0.001). Similar results were obtained with the VASP assay. Both prasugrel and ticagrelor had markedly lower HPR rates than clopidogrel and very high rates of LPR at both time points.

CONCLUSIONS

Prasugrel and ticagrelor displayed more potent and consistent PD effects than clopidogrel in ACS patients undergoing PCI, with a trend towards greater platelet inhibition with ticagrelor during the maintenance phase of therapy compared to prasugrel.

Impaired aspirin-mediated platelet function inhibition in resuscitated patients with acute myocardial infarction treated with therapeutic hypothermia: a prospective, observational, non-randomized single-centre study

The majority of resuscitated patients present with underlying cardiac disease, and out of these myocardial infarction is most common. Immediate interventional treatment is recommended and routinely requires dual antiplatelet therapy including aspirin and a P2Y12-inhibitor. Therapeutic hypothermia or target temperature management is also recommended in these patients. Cardiogenic shock as well as reduced body temperature impacts platelet reactivity and its medical inhibition. The study aims to quantify aspirin- and P2Y12-mediated platelet inhibition in patients presenting with myocardial infarction and cardiopulmonary resuscitation. Twenty-five resuscitated patients were enrolled in this prospective, observational, non-randomized single-centre study. These patients were compared to 77 matched controls from the ATLANTIS-ACS database of non-resuscitated patients with myocardial infarction. Platelet function testing was performed by light transmittance aggregometry. Aspirin reactivity was monitored by inducing platelet aggregation with collagen and arachidonic acid, respectively. P2Y12 inhibition was recorded by stimulation of platelet aggregation with adenosine diphosphate. To quantify the overall platelet response, thrombin receptor-activated peptide was used. Aspirin-mediated platelet reactivity decreased significantly in resuscitated patients during the first days and was significantly weaker on day 3 (collagen AUC 253.8 (122.7–352.2) vs. 109.0 (73.0–182.0); p = 0.022). P2Y12-mediated platelet inhibition was also impaired in resuscitated patients on day 3 (mean ADP AUC (IQR): CPR 172.1 (46.7−346.5) vs. control 43.9 (18.9–115.2); p < 0.05). Aspirin- and P2Y12-mediated platelet inhibition is impaired in resuscitated patients treated with therapeutic hypothermia. On day 3, we recorded lowest inhibitory effects of both drug types and patients might be at particular risk at that time. Potentially, intravenous aspirin and P2Y12 inhibitors might still supply a more predictable and stable platelet inhibition.

Role of New Antiplatelet Drugs on Cardiovascular Disease: Update on Cangrelor

Dual therapy with a P2Y₁₂ receptor antagonist in addition to aspirin is the antiplatelet treatment of choice in patients with acute coronary syndromes or undergoing percutaneous coronary intervention (PCI). However, available oral P2Y₁₂ antagonists have several limitations, mostly due to their pharmacological profile, which can affect outcomes in certain clinical settings. Cangrelor is an intravenous, direct-acting, potent P2Y₁₂ inhibitor with rapid onset and offset of action, which has been recently approved for clinical use in patients undergoing PCI. In clinical trials, cangrelor has demonstrated greater efficacy than clopidogrel with a favorable safety profile among PCI patients not receiving pretreatment with oral P2Y₁₂ antagonists. However, its definitive role in contemporary practice is yet to be determined. This review aims to provide a comprehensive overview of the current status of knowledge on cangrelor, focusing on its pharmacological properties, clinical development, and the potential applications of this newly available agent.

ABCC3 Polymorphisms and mRNA Expression Influence the Concentration of a Carboxylic Acid Metabolite in Patients on Clopidogrel and Aspirin Therapy

Acetylsalicylic acid (ASA) and clopidogrel combined therapy has been reported to be beneficial in patients with acute coronary syndrome (ACS). Antiplatelet drug resistance, especially to clopidogrel, is a multifactorial phenomenon that affects a large number of ACS patients. The genetic contribution to this drug response is not fully elucidated. We investigated the relationship of ABC-type efflux subfamily C member 3 (ABCC3) polymorphisms and mRNA expression with plasma concentrations of clopidogrel, salicylic acid (SA) and a carboxylic acid metabolite (CAM). Clopidogrel, CAM and SA plasma concentrations were measured simultaneously by liquid chromatography-tandem mass spectrometry (LCMS/MS) from 83 ACS patients undergoing percutaneous coronary intervention. ABCC3 (rs757421, rs733392 and rs739923) and CYP2C19*2 (rs4244285) polymorphisms as well as mRNA expression were evaluated. A positive correlation was found between CAM concentrations and ABCC3 mRNA expression (r = 0.494, p < 0.0001). Patients carrying genotype AA (rs757421 variant) had higher CAM concentrations and ABCC3 mRNA expression as compared to those of GG + GA carriers (p = 0.017). A multiple linear regression analysis revealed that ABCC3 mRNA expression (p = 0.017), rs757421 AA genotype (p = 0.001), blood collection time (p = 0.018) and clopidogrel dose (p = 0.001) contributed to the concentration of CAM. No associations were observed for the CYP2C19*2 polymorphism. These results suggest that up-regulation of ABCC3 mRNA expression leads to increased plasma CAM levels through MRP3-mediated cell efflux. The ABCC3 rs757421 polymorphism may contribute to gene expression. Therefore, ABCC3 may be a potential biomarker for the response to clopidogrel.

Effect of temperature on platelet adherence

BACKGROUND

Thrombogenicity is one of the main parameters tested in vitro to evaluate the hemocompatibility of artificial surfaces. While the influence of the temperature on platelet aggregation has been addressed by several studies, the temperature influence on the adherence of platelets to body foreign surfaces as an important aspect of biomedical device handling has not yet been explored. Therefore, we analyzed the influence of two typically applied incubation-temperatures (22°C and 37°C) on the adhesion of platelets to biomaterials.

MATERIAL AND METHODS

Thrombogenicity of three different polymers - medical grade poly(dimethyl siloxane) (PDMS), polytetrafluoroethylene (PTFE) and polyethylene terephthalate (PET) - were studied in an in vitro static test. Platelet adhesion was studied with stringently characterized blood from apparently healthy subjects. Collection of whole blood and preparation of platelet rich plasma (PRP) was carried out at room temperature (22°C). PRP was incubated with the polymers either at 22°C or 37°C. Surface adherent platelets were fixed, fluorescently labelled and assessed by an image-based approach.

RESULTS AND DISCUSSION

Differences in the density of adherent platelets after incubation at 22°C and 37°C occurred on PDMS and PET. Similar levels of adherent platelets were observed on the very thrombogenic PTFE. The covered surface areas per single platelet were analyzed to measure the state of platelet activation and revealed no differences between the two incubation temperatures for any of the analyzed polymers. Irrespective of the observed differences between the low and medium thrombogenic PDMS and PET and the higher variability at 22°C, the thrombogenicity of the three investigated polymers was evaluated being comparable at both incubation temperatures.

Effect of Hypothermia and Targeted Temperature Management on Drug Disposition and Response Following Cardiac Arrest: A Comprehensive Review of Preclinical and Clinical Investigations

Targeted temperature management (TTM) has been shown to reduce mortality and improve neurological outcomes in out-of-hospital cardiac arrest (CA) patients and in neonates with hypoxic-ischemic encephalopathy (HIE). TTM has also been associated with adverse drug events in the critically ill patient due to its effect on drug pharmacokinetics (PKs) and pharmacodynamics (PDs). We aim to evaluate the current literature on the effect of TTM on drug PKs and PDs following CA. MEDLINE/PubMed databases were searched for publications, which include the MeSH terms hypothermia, drug metabolism, drug transport, P450, critical care, cardiac arrest, hypoxic-ischemic encephalopathy, pharmacokinetics, and pharmacodynamics between July 2006 and October 2015. Twenty-three studies were included in this review. The studies demonstrate that hypothermia impacts PK parameters and increases concentrations of cytochrome-P450-metabolized drugs in the cooling and rewarming phase. Furthermore, the current data demonstrate a combined effect of CA and hypothermia on drug PK. Importantly, these effects can last greater than 4-5 days post-treatment. Limited evidence suggests hypothermia-mediated changes in the Phase II metabolism and the Phase III transport of drugs. Hypothermia also has been shown to potentially decrease the effect of specific drugs at the receptor level. Therapeutic hypothermia, as commonly deployed/applied during TTM, alters PK, and elevates concentrations of several commonly used medications. Hypothermia-mediated effects are an important factor when dosing and monitoring patients undergoing TTM treatment.

Platelet inhibition with prasugrel in patients with acute myocardial infarction undergoing therapeutic hypothermia after cardiopulmonary resuscitation

Acute myocardial infarction (AMI) is the leading cause for out-of-hospital cardiac arrest. Therapeutic hypothermia improves neurological outcome in combination with early revascularisation, but seems to affect clopidogrel responsiveness. The more potent thienopyridine prasugrel has not yet been sufficiently evaluated during therapeutic hypothermia. We investigated 23 consecutive AMI patients (61 ± 11 years) following out-of-hospital resuscitation undergoing revascularisation and therapeutic hypothermia. Prasugrel efficacy was assessed by the platelet-reactivity-index (PRI) before and 2, 4, 6, 12, 24, 48, and 72 hours (h) following a loading dose of 60 mg via a gastric tube. Mean PRI (± SD) was 70 ± 12 % prior to loading and 60 ± 16 % (2 h, ns), 52 ± 21 % (4 h, p< 0.01), 42 ± 26 % (6 h, p< 0.01), 37 ± 21 % (12 h, p< 0.01), 27 ± 23 % (24 h, p< 0.01), 18 ± 14 % (48 h, p< 0.01), and 13 ± 10 % (72 h, p< 0.01) after loading. Sufficient platelet inhibition occurred later compared to stable AMI patients (6 h vs 2 h); however, high on-treatment platelet reactivity significantly decreased over time and was non-existent after 72 h (PRI> 50 %: 2 h: 72 %, 4 h: 52 %, 6 h: 43 %, 12 h: 29 %, 24 h: 17 %, 48 h: 5 %, 72 h: 0 %). There was no relation between 30-day mortality rate (26 %) and PRI values. Prasugrel significantly reduced platelet reactivity even during vasopressor use, analgosedation and therapeutic hypothermia. Despite a significant delay compared to stable AMI patients, sufficient platelet inhibition was reached in 83 % of patients within 24 h. Therefore, prasugrel administration via gastric tube might be a useful therapeutic strategy in these patients at high risk, providing potent and effective P2Y12 inhibition.

Temperature effects on haemostasis in whole blood from ticagrelor- and aspirin-treated patients with acute coronary syndrome

BACKGROUND

Comatose survivors after cardiac arrest are treated with mild induced hypothermia and potent platelet- inhibiting drugs after coronary stenting. Previous studies have shown an increased incidence of stent thrombosis during clopidogrel and aspirin treatment in conjunction with induced hypothermia. The aim of this study was to investigate the in vitro effect of induced hypo- and hyperthermia on blood from patients undergoing ticagrelor- and aspirin-mediated platelet inhibition.

METHODS

Whole blood from 15 patients with acute coronary syndrome who were treated with ticagrelor and aspirin and from eight healthy volunteers was incubated for 1 hour at 28, 33, 37, and 39°C.

RESULTS

In blood from patients with acute coronary syndrome, the activated clotting time (Sonoclot) was prolonged in mild hypothermic (33°C) compared to normothermic (37°C) samples. Sonoclot, clotting rate and platelet function were decreased in hypothermic compared to normothermic samples. Platelet-induced activation and aggregation (Multiplate) was unchanged in mild hypothermic compared to normothermic samples. In contrast, mild hypothermia supported increased platelet activation as measured with flow cytometry with up-regulation of PAC-1 and P-selectin on the platelet surface.

CONCLUSION

In acute coronary syndrome patients treated with ticagrelor and aspirin, in vitro hypothermia to 33°C markedly increased platelet activity measured with flow cytometry, whereas viscoelastic coagulation test (Sonoclot) revealed a hypocoagulative response. Prospective clinical trials studying platelet inhibition at different temperatures and correlating changes in platelet function to bleeding or stent occlusion are needed.