Effect of Antiplatelet Therapy on Survival and Organ Support-Free Days in Critically Ill Patients With COVID-19: A Randomized Clinical Trial

Therapeutic advances in COVID-19

Over 2 years have passed since the start of the COVID-19 pandemic, which has claimed millions of lives. Unlike the early days of the pandemic, when management decisions were based on extrapolations from in vitro data, case reports and case series, clinicians are now equipped with an armamentarium of therapies based on high-quality evidence. These treatments are spread across seven main therapeutic categories: anti-inflammatory agents, antivirals, antithrombotics, therapies for acute hypoxaemic respiratory failure, anti-SARS-CoV-2 (neutralizing) antibody therapies, modulators of the renin-angiotensin-aldosterone system and vitamins. For each of these treatments, the patient population characteristics and clinical settings in which they were studied are important considerations. Although few direct comparisons have been performed, the evidence base and magnitude of benefit for anti-inflammatory and antiviral agents clearly outweigh those of other therapeutic approaches such as vitamins. The emergence of novel variants has further complicated the interpretation of much of the available evidence, particularly for antibody therapies. Importantly, patients with acute and chronic kidney disease were under-represented in many of the COVID-19 clinical trials, and outcomes in this population might differ from those reported in the general population. Here, we examine the clinical evidence for these therapies through a kidney medicine lens.

Effect of extracorporeal hemoadsorption in critically ill patients with COVID-19: A narrative review

COVID-19 has been affecting the world unprecedentedly and will remain widely prevalent due to its elusive pathophysiological mechanism and the continuous emergence of new variants. Critically ill patients with COVID-19 are commonly associated with cytokine storm, multiple organ dysfunction, and high mortality. To date, growing evidence has shown that extracorporeal hemoadsorption can exert its adjuvant effect to standard of care by regulating immune homeostasis, reducing viremia, and decreasing endotoxin activity in critically ill COVID-19 cases. However, the selection of various hemofilters, timing of initiation and termination of hemoadsorption therapy, anticoagulation management of extracorporeal circuits, identification of target subgroups, and ultimate survival benefit remain controversial. The purpose of this narrative review is to comprehensively summarize the rationale for the use of hemoadsorption in critically ill patients with COVID-19 and to gather the latest clinical evidence in this field.

Thrombosis questions from the inpatient wards

The multifaceted pathophysiologic processes that comprise thrombosis and thromboembolic diseases take on a particular urgency in the hospitalized setting. In this review, we explore 3 cases of thrombosis from the inpatient wards: purpura fulminans, cancer-associated thrombosis with thrombocytopenia, and coronavirus disease 2019 (COVID-19) and the use of dose-escalated anticoagulation therapy and antiplatelet agents. We discuss the evaluation and management of purpura fulminans and the roles of plasma transfusion, protein C and antithrombin replacement, and anticoagulation in treating this disease. We present a framework for evaluating the etiologies of thrombocytopenia in cancer and review 2 strategies for anticoagulation management in patients with cancer-associated thrombosis and thrombocytopenia, including recent prospective data supporting the use of dose-modified anticoagulation based on platelet count. Last, we dissect the major clinical trials of therapeutic- and intermediate-dose anticoagulation and antiplatelet therapy in hospitalized patients with COVID-19, reviewing key recommendations from consensus guidelines while highlighting ways in which institutional and patient-tailored practices regarding antithrombotic therapies in COVID-19 may differ. Together, the cases highlight the diverse and dramatic presentations of macro- and microvascular thrombosis as encountered on the inpatient wards.

Gaps and opportunities in sepsis translational research

Infection initiates sepsis, but the clinical disease arises through the innate immune response of the host. A rapidly evolving understanding of the biology of that response has not been paralleled by the development of successful new treatment. The COVID-19 pandemic has begun to change this revealing the promise of distinct therapeutic approaches and the feasibility of new approaches to evaluate them. We review the history of mediator-targeted therapy for sepsis and explore the conceptual, biological, technological, and organizational challenges that must be addressed to enable the development of effective treatments for a leading cause of global morbidity and mortality.

Surging ICU during COVID-19 pandemic: an overview

PURPOSE OF REVIEW

The coronavirus disease 2019 (COVID-19) pandemic has posed great challenges to intensive care units (ICUs) across the globe. The objective of this review is to provide an overview on how ICU surging was managed during COVID-19 pandemic, with a special focus on papers published in the last 18 months.

RECENT FINDINGS

From the onset of the COVID-19 pandemic, it was apparent that the biggest challenge was the inequity of access to an adequately equipped and staffed ICU bed. The first wave was overwhelming; large surge of patients required critical care, resources were limited and non-COVID-19 care processes were severely compromised. Various approaches were used to address ICU staffing shortage and to expand the physical ICU space capacity. Because of restrictions to family visitations in most ICUs, the pandemic posed a threat to communication and family-centered ICU care. The pandemic, especially during the first wave, was accompanied by a high level of apprehension in the community, many uncertainties about clinical course and therapy and an influx of speculations and misinformation.

SUMMARY

Although healthcare systems learned how to face some of the challenges with subsequent waves, the pandemic had persistent effects on healthcare systems.

Colchicine and the combination of rivaroxaban and aspirin in patients hospitalised with COVID-19 (ACT): an open-label, factorial, randomised, controlled trial

BACKGROUND

COVID-19 disease is accompanied by a dysregulated immune response and hypercoagulability. The Anti-Coronavirus Therapies (ACT) inpatient trial aimed to evaluate anti-inflammatory therapy with colchicine and antithrombotic therapy with the combination of rivaroxaban and aspirin for prevention of disease progression in patients hospitalised with COVID-19.

METHODS

The ACT inpatient, open-label, 2 × 2 factorial, randomised, controlled trial was done at 62 clinical centres in 11 countries. Patients aged at least 18 years with symptomatic, laboratory confirmed COVID-19 who were within 72 h of hospitalisation or worsening clinically if already hospitalised were randomly assigned (1:1) to receive colchicine 1·2 mg followed by 0·6 mg 2 h later and then 0·6 mg twice daily for 28 days versus usual care; and in a second (1:1) randomisation, to the combination of rivaroxaban 2·5 mg twice daily plus aspirin 100 mg once daily for 28 days versus usual care. Investigators and patients were not masked to treatment allocation. The primary outcome, assessed at 45 days in the intention-to-treat population, for the colchicine randomisation was the composite of the need for high-flow oxygen, mechanical ventilation, or death; and for the rivaroxaban plus aspirin randomisation was the composite of major thrombosis (myocardial infarction, stroke, acute limb ischaemia, or pulmonary embolism), the need for high-flow oxygen, mechanical ventilation, or death. The trial is registered at www.

CLINICALTRIALS

gov, NCT04324463 and is ongoing.

FINDINGS

Between Oct 2, 2020, and Feb 10, 2022, at 62 sites in 11 countries, 2749 patients were randomly assigned to colchicine or control and the combination of rivaroxaban and aspirin or to the control. 2611 patients were included in the analysis of colchicine (n=1304) versus control (n=1307); 2119 patients were included in the analysis of rivaroxaban and aspirin (n=1063) versus control (n=1056). Follow-up was more than 98% complete. Overall, 368 (28·2%) of 1304 patients allocated to colchicine and 356 (27·2%) of 1307 allocated to control had a primary outcome (hazard ratio [HR] 1·04, 95% CI 0·90-1·21, p=0·58); and 281 (26·4%) of 1063 patients allocated to the combination of rivaroxaban and aspirin and 300 (28·4%) of 1056 allocated to control had a primary outcome (HR 0·92, 95% CI 0·78-1·09, p=0·32). Results were consistent in subgroups defined by vaccination status, disease severity at baseline, and timing of randomisation in relation to onset of symptoms. There was no increase in the number of patients who had at least one serious adverse event for colchicine versus control groups (87 [6·7%] of 1304 vs 90 [6·9%] of 1307) or with rivaroxaban and aspirin versus control groups (85 [8·0%] vs 91 [8·6%]). Among patients assigned to colchicine, 8 (0·61%) had adverse events that led to discontinuation of study drug, mostly gastrointestinal in nature. 17 (1·6%) patients assigned to the combination of rivaroxaban and aspirin had bleeding compared with seven (0·66%) of those allocated to control (p=0·042); the number of serious bleeding events was two (0·19%) versus six (0·57%), respectively (p=0·18). No patients assigned to rivaroxaban and aspirin had serious adverse events that led to discontinuation of study drug.

INTERPRETATION

Among patients hospitalised with COVID-19, neither colchicine nor the combination of rivaroxaban and aspirin prevent disease progression or death.

FUNDING

Canadian Institutes for Health Research, Bayer, Population Health Research Institute, Hamilton Health Sciences Research Institute, Thistledown Foundation.

TRANSLATIONS

For the Portuguese, Russian and Spanish translations of the abstract see Supplementary Materials section.

Anticoagulation and Antiplatelet Therapy for Prevention of Venous and Arterial Thrombotic Events in Critically Ill Patients With COVID-19: COVID-PACT

BACKGROUND

The efficacy and safety of prophylactic full-dose anticoagulation and antiplatelet therapy in critically ill COVID-19 patients remain uncertain.

METHODS

COVID-PACT (Prevention of Arteriovenous Thrombotic Events in Critically-ill COVID-19 Patients Trial) was a multicenter, 2×2 factorial, open-label, randomized-controlled trial with blinded end point adjudication in intensive care unit-level patients with COVID-19. Patients were randomly assigned to a strategy of full-dose anticoagulation or standard-dose prophylactic anticoagulation. Absent an indication for antiplatelet therapy, patients were additionally randomly assigned to either clopidogrel or no antiplatelet therapy. The primary efficacy outcome was the hierarchical composite of death attributable to venous or arterial thrombosis, pulmonary embolism, clinically evident deep venous thrombosis, type 1 myocardial infarction, ischemic stroke, systemic embolic event or acute limb ischemia, or clinically silent deep venous thrombosis, through hospital discharge or 28 days. The primary efficacy analyses included an unmatched win ratio and time-to-first event analysis while patients were on treatment. The primary safety outcome was fatal or life-threatening bleeding. The secondary safety outcome was moderate to severe bleeding. Recruitment was stopped early in March 2022 (≈50% planned recruitment) because of waning intensive care unit-level COVID-19 rates.

RESULTS

At 34 centers in the United States, 390 patients were randomly assigned between anticoagulation strategies and 292 between antiplatelet strategies (382 and 290 in the on-treatment analyses). At randomization, 99% of patients required advanced respiratory therapy, including 15% requiring invasive mechanical ventilation; 40% required invasive ventilation during hospitalization. Comparing anticoagulation strategies, a greater proportion of wins occurred with full-dose anticoagulation (12.3%) versus standard-dose prophylactic anticoagulation (6.4%; win ratio, 1.95 [95% CI, 1.08-3.55]; P=0.028). Results were consistent in time-to-event analysis for the primary efficacy end point (full-dose versus standard-dose incidence 19/191 [9.9%] versus 29/191 [15.2%]; hazard ratio, 0.56 [95% CI, 0.32-0.99]; P=0.046). The primary safety end point occurred in 4 (2.1%) on full dose and in 1 (0.5%) on standard dose (P=0.19); the secondary safety end point occurred in 15 (7.9%) versus 1 (0.5%; P=0.002). There was no difference in all-cause mortality (hazard ratio, 0.91 [95% CI, 0.56-1.48]; P=0.70). There were no differences in the primary efficacy or safety end points with clopidogrel versus no antiplatelet therapy.

CONCLUSIONS

In critically ill patients with COVID-19, full-dose anticoagulation, but not clopidogrel, reduced thrombotic complications with an increase in bleeding, driven primarily by transfusions in hemodynamically stable patients, and no apparent excess in mortality.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT04409834.

A case of multiple thrombosis and septic shock in a critically ill patient with Omicron infection

The emergence of the acute respiratory syndrome coronavirus 2 variant named Omicron has become a global concern. A 74-year-old unvaccinated patient was critically ill infected with the Omicron variant characterised by septic shock, large-scale cerebral embolism, deep vein thrombosis, and multiple organ dysfunction with respiratory failure, acute renal failure, coagulation dysfunction. The clinical symptoms were successfully controlled by active rescue treatment such as anti-infection, anti-shock, implantation of a vena cava filter as well as multi-organ function support. Although there are many complications in critically ill patients with Omicron variant infections, especially coagulation disorders and thrombosis, they can be resolved with a combination of Chinese and Western medicine positive rescue.

Platform trials for anaesthesia and perioperative medicine: a narrative review

Large randomised trials provide the most reliable evidence of effectiveness of new treatments in clinical practice. However, the time and resources required to complete such trials can be daunting. An overarching clinical trial platform focused on a single condition or type of surgery, aiming to compare several treatments, with an option to stop any or add in new treatment options, can provide greater efficiency. This has the potential to accelerate knowledge acquisition and identify effective, ineffective, or harmful treatments faster. The master protocol of the platform defines the study population(s) and standardised procedures. Ineffective or harmful treatments can be discarded or study drug dose modified during the life cycle of the trial. Other adaptive elements that can be modified include eligibility criteria, required sample size for any comparison(s), randomisation assignment ratio, and the addition of other promising treatment options. There are excellent opportunities for anaesthetists to establish platform trials in perioperative medicine. Platform trials are highly efficient, with the potential to provide quicker answers to important clinical questions that lead to improved patient care.

Practical Recommendations for Optimal Thromboprophylaxis in Patients with COVID-19: A Consensus Statement Based on Available Clinical Trials

Coronavirus disease 2019 (COVID-19) has been shown to be strongly associated with increased risk for venous thromboembolism events (VTE) mainly in the inpatient but also in the outpatient setting. Pharmacologic thromboprophylaxis has been shown to offer significant benefits in terms of reducing not only VTE events but also mortality, especially in acutely ill patients with COVID-19. Although the main source of evidence is derived from observational studies with several limitations, thromboprophylaxis is currently recommended for all hospitalized patients with acceptable bleeding risk by all national and international guidelines. Recently, high quality data from randomized controlled trials (RCTs) further support the role of thromboprophylaxis and provide insights into the optimal thromboprophylaxis strategy. The aim of this statement is to systematically review all the available evidence derived from RCTs regarding thromboprophylaxis strategies in patients with COVID-19 in different settings (either inpatient or outpatient) and provide evidence-based guidance to practical questions in everyday clinical practice. Clinical questions accompanied by practical recommendations are provided based on data derived from 20 RCTs that were identified and included in the present study. Overall, the main conclusions are: (i) thromboprophylaxis should be administered in all hospitalized patients with COVID-19, (ii) an optimal dose of inpatient thromboprophylaxis is dependent upon the severity of COVID-19, (iii) thromboprophylaxis should be administered on an individualized basis in post-discharge patients with COVID-19 with high thrombotic risk, and (iv) thromboprophylaxis should not be routinely administered in outpatients. Changes regarding the dominant SARS-CoV-2 variants, the wide immunization status (increasing rates of vaccination and reinfections), and the availability of antiviral therapies and monoclonal antibodies might affect the characteristics of patients with COVID-19; thus, future studies will inform us about the thrombotic risk and the optimal therapeutic strategies for these patients.

Associations between the use of aspirin or other antiplatelet drugs and all-cause mortality among patients with COVID-19: A meta-analysis

Introduction: Whether aspirin or other antiplatelet drugs can reduce mortality among patients with coronavirus disease (COVID-19) remains controversial.

Methods: We identified randomized controlled trials, prospective cohort studies, and retrospective studies on associations between aspirin or other antiplatelet drug use and all-cause mortality among patients with COVID-19 in the PubMed database between March 2019 and September 2021. Newcastle–Ottawa Scale and Cochrane Risk of Bias Assessment Tool were used to assess the risk of bias. The I2 statistic was used to assess inconsistency among trial results. The summary risk ratio (RR) and odds ratio (OR) were obtained through the meta-analysis.

Results: The 34 included studies comprised three randomized controlled trials, 27 retrospective studies, and 4 prospective cohort studies. The retrospective and prospective cohort studies showed low-to-moderate risks of bias per the Newcastle–Ottawa Scale score, while the randomized controlled trials showed low-to-high risks of bias per the Cochrane Risk of Bias Assessment Tool. The randomized controlled trials showed no significant effect of aspirin use on all-cause mortality in patients with COVID-19 {risk ratio (RR), 0.96 [95% confidence interval (CI) 0.90–1.03]}. In retrospective studies, aspirin reduced all-cause mortality in patients with COVID-19 by 20% [odds ratio (OR), 0.80 (95% CI 0.70–0.93)], while other antiplatelet drugs had no significant effects. In prospective cohort studies, aspirin decreased all-cause mortality in patients with COVID-19 by 15% [OR, 0.85 (95% CI 0.80–0.90)].

Conclusion: The administration of aspirin may reduce all-cause mortality in patients with COVID-19.

Concomitant renal and splenic infarctions in a COVID-19-patient with a catastrophic thrombotic syndrome

Since the outbreak of the COVID-19 pandemic, thrombotic events have been accurately described in patients infected by the SARS-CoV-2, especially venous thromboembolism. However, the mystery of arterial thrombosis is still unclear. Here, we report the case of a 59-year-old man with diabetes mellitus, admitted for COVID-19-pneumonia complicated by pulmonary embolism, a thrombus in the aortic isthmus, the descending thoracic aorta associated with splenic and left renal infarctions, and an acute right limb ischemia. The etiological assessment of this catastrophic thrombotic syndrome showed no evidence for preexisting inherited or acquired thrombophilia. Our case emphasizes the hypercoagulability state in COVID-19-patient leading to both arterial and venous thromboembolisms and the need to establish adequate strategies for the diagnosis and management of thrombo-embolisms to prevent these potentially fatal complications.

ISTH guidelines for antithrombotic treatment in COVID-19

Antithrombotic agents reduce risk of thromboembolism in severely ill patients. Patients with coronavirus disease 2019 (COVID-19) may realize additional benefits from heparins. Optimal dosing and timing of these treatments and benefits of other antithrombotic agents remain unclear. In October 2021, ISTH assembled an international panel of content experts, patient representatives, and a methodologist to develop recommendations on anticoagulants and antiplatelet agents for patients with COVID-19 in different clinical settings. We used the American College of Cardiology Foundation/American Heart Association methodology to assess level of evidence (LOE) and class of recommendation (COR). Only recommendations with LOE A or B were included. Panelists agreed on 12 recommendations: three for non-hospitalized, five for non-critically ill hospitalized, three for critically ill hospitalized, and one for post-discharge patients. Two recommendations were based on high-quality evidence, the remainder on moderate-quality evidence. Among non-critically ill patients hospitalized for COVID-19, the panel gave a strong recommendation (a) for use of prophylactic dose of low molecular weight heparin or unfractionated heparin (LMWH/UFH) (COR 1); (b) for select patients in this group, use of therapeutic dose LMWH/UFH in preference to prophylactic dose (COR 1); but (c) against the addition of an antiplatelet agent (COR 3). Weak recommendations favored (a) sulodexide in non-hospitalized patients, (b) adding an antiplatelet agent to prophylactic LMWH/UFH in select critically ill, and (c) prophylactic rivaroxaban for select patients after discharge (all COR 2b). Recommendations in this guideline are based on high-/moderate-quality evidence available through March 2022. Focused updates will incorporate future evidence supporting changes to these recommendations.

Understanding COVID-19-associated coagulopathy

COVID-19-associated coagulopathy (CAC) is a life-threatening complication of SARS-CoV-2 infection. However, the underlying cellular and molecular mechanisms driving this condition are unclear. Evidence supports the concept that CAC involves complex interactions between the innate immune response, the coagulation and fibrinolytic pathways, and the vascular endothelium, resulting in a procoagulant condition. Understanding of the pathogenesis of this condition at the genomic, molecular and cellular levels is needed in order to mitigate thrombosis formation in at-risk patients. In this Perspective, we categorize our current understanding of CAC into three main pathological mechanisms: first, vascular endothelial cell dysfunction; second, a hyper-inflammatory immune response; and last, hypercoagulability. Furthermore, we pose key questions and identify research gaps that need to be addressed to better understand CAC, facilitate improved diagnostics and aid in therapeutic development. Finally, we consider the suitability of different animal models to study CAC.

Good practice statements for antithrombotic therapy in the management of COVID-19: Guidance from the SSC of the ISTH

Despite the emergence of high quality randomized trial data with the use of antithrombotic agents to reduce the risk of thromboembolism, end-organ failure, and possibly mortality in patients with coronavirus disease 2019 (COVID-19), questions still remain as to optimal patient selection for these strategies, the use of antithrombotics in outpatient settings and in-hospital settings (including critical care units), thromboprophylaxis in special patient populations, and the management of acute thrombosis in hospitalized COVID-19 patients. In October 2021, the International Society on Thrombosis and Haemostasis (ISTH) formed a multidisciplinary and international panel of content experts, two patient representatives, and a methodologist to develop recommendations on treatment with anticoagulants and antiplatelet agents for COVID-19 patients. The ISTH Guideline panel discussed additional topics to be well suited to a non-Grading of Recommendations Assessment, Development, and Evaluation (GRADE) for Good Practice Statements (GPS) to support good clinical care in the antithrombotic management of COVID-19 patients in various clinical settings. The GPS panel agreed on 17 GPS: 3 in the outpatient (pre-hospital) setting, 12 in the hospital setting both in non-critical care (ward) as well as intensive care unit settings, and 2 in the immediate post-hospital discharge setting based on limited evidence or expert opinion that supports net clinical benefit in enacting the statements provided. The antithrombotic therapies discussed in these GPS should be available in low- and middle-income countries.

The impact of platelets on pulmonary microcirculation throughout COVID-19 and its persistent activating factors

Patients with COVID-19 often have hypoxemia, impaired lung function, and abnormal imaging manifestations in acute and convalescent stages. Alveolar inflammation, pulmonary vasculitis, and thromboembolism synergistically damage the blood-air barrier, resulting in increased pulmonary permeability and gas exchange disorders. The incidence of low platelet counts correlates with disease severity. Platelets are also involved in the impairment of pulmonary microcirculation leading to abnormal lung function at different phases of COVID-19. Activated platelets lose the ability to protect the integrity of blood vessel walls, increasing the permeability of pulmonary microvasculature. High levels of platelet activation markers are observed in both mild and severe cases, short and long term. Therefore, the risk of thrombotic events may always be present. Vascular endothelial injury, immune cells, inflammatory mediators, and hypoxia participate in the high reactivity and aggregation of platelets in various ways. Microvesicles, phosphatidylserine (PS), platelets, and coagulation factors are closely related. The release of various cell-derived microvesicles can be detected in COVID-19 patients. In addition to providing a phospholipid surface for the synthesis of intrinsic factor Xase complex and prothrombinase complex, exposed PS also promotes the decryption of tissue factor (TF) which then promotes coagulant activity by complexing with factor VIIa to activate factor X. The treatment of COVID-19 hypercoagulability and thrombosis still focuses on early intervention. Antiplatelet therapy plays a role in relieving the disease, inhibiting the formation of the hypercoagulable state, reducing thrombotic events and mortality, and improving sequelae. PS can be another potential target for the inhibition of hypercoagulable states.

Antiplatelet therapy for patients with COVID-19: Systematic review and meta-analysis of observational studies and randomized controlled trials

Background

Hyperinflammation and coagulopathy are hallmarks of COVID-19 and synergistically contribute to illness progression. Antiplatelet agents have been proposed as candidate drugs for COVID-19 treatment on the basis of their antithrombotic and anti-inflammatory properties. A systematic review and meta-analysis that included early observational studies and recent randomized controlled trials (RCTs) was performed to summarize and compare evidence on this issue.

Methods

PubMed, Embase, and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched to identify studies published up to Nov 7, 2021, and the results of registered clinical trials were followed up to Mar 30, 2022. We included RCTs and observational studies assessing the effect of antiplatelet therapy in adult patients with COVID-19. Data on baseline patient characteristics, interventions, controls, and outcomes were extracted by two independent reviewers. The primary outcome was mortality. Data were pooled using a random-effects model.

Results

Twenty-seven studies were included, of which 23 observational studies were pooled in a meta-analysis, and the remaining four RCTs (ACTIV-4B, RECOVERY, ACTIV-4a, and REMAP-CAP) were narratively synthesized. Based on 23 observational studies of 87,824 COVID-19 patients, antiplatelet treatment favors a lower risk of mortality [odds ratio (OR) 0.72, 95% confidence interval (CI) 0.61–0.85; I² = 87.0%, P < 0.01]. The narrative synthesis of RCTs showed conflicting evidence, which did not support adding antiplatelet therapy to the standard care, regardless of the baseline illness severity and concomitant anticoagulation intensity.

Conclusion

While the rationale for using antiplatelet treatment in COVID-19 patients is compelling and was supported by the combined result of early observational studies, evidence from RCTs did not confirm this approach. Several factors that could explain this inconsistency were highlighted alongside perspectives on future research directions.

Thromboinflammation: From Atherosclerosis to COVID-19

The activating interplay of thrombosis and inflammation (thromboinflammation) has been established as a major underlying pathway, driving not only cardiovascular disease but also autoimmune disease and most recently, COVID-19. Throughout the years, innate immune cells have emerged as important modulators of this process. As the most abundant white blood cell in humans, neutrophils are well-positioned to propel thromboinflammation. This includes their ability to trigger an organized cell death pathway with the release of decondensed chromatin structures called neutrophil extracellular traps. Decorated with histones and cytoplasmic and granular proteins, neutrophil extracellular traps exert cytotoxic, immunogenic, and prothrombotic effects accelerating disease progression. Distinct steps leading to extracellular DNA release (NETosis) require the activities of PAD4 (protein arginine deiminase 4) catalyzing citrullination of histones and are supported by neutrophil inflammasome. By linking the immunologic function of neutrophils with the procoagulant and proinflammatory activities of monocytes and platelets, PAD4 activity holds important implications for understanding the processes that fuel thromboinflammation. We will also discuss mechanisms whereby vascular occlusion in thromboinflammation depends on the interaction of neutrophil extracellular traps with ultra-large VWF (von Willebrand Factor) and speculate on the importance of PAD4 in neutrophil inflammasome assembly and neutrophil extracellular traps in thromboinflammatory diseases including atherosclerosis and COVID-19.

Failed clinical trials on COVID-19 acute respiratory distress syndrome in hospitalized patients: common oversights and streamlining the development of clinically effective therapeutics

INTRODUCTION

The coronavirus disease 2019 (COVID-19) pandemic has put a strain on global healthcare systems. Despite admirable efforts to develop rapidly new pharmacotherapies, supportive treatments remain the standard of care. Multiple clinical trials have failed due to design issues, biased patient enrollment, small sample sizes, inadequate control groups, and lack of long-term outcomes monitoring.

AREAS COVERED

This narrative review depicts the current situation around failed and success COVID-19 clinical trials and recommendations in hospitalized patients with COVID-19, oversights and streamlining of clinically effective therapeutics. PubMed, EBSCO, Cochrane Library, and WHO and NIH guidelines were searched for relevant literature up to 5 August 2022.

EXPERT OPINION

The WHO, NIH, and IDSA have issued recommendations to better clarify which drugs should be used during the different phases of the disease. Given the biases and high heterogeneity of published studies, interpretation of the current literature is difficult. Future clinical trials should be designed to standardize clinical approaches, with appropriate organization, patient selection, addition of control groups, and careful identification of disease phase to reduce heterogeneity and bias and should rely on the integration of scientific societies to promote a consensus on interpretation of the data and recommendations for optimal COVID-19 therapies.

Coagulopathy in COVID-19 and anticoagulation clinical trials

Severe acute respiratory disease coronavirus 2 (SARS-COV-2) first emerged in Wuhan, China, in December 2019 and has caused a global pandemic of a scale unprecedented in the modern era. People infected with SARS-CoV-2 can be asymptomatic, moderate symptomatic or develop severe COVID-19. Other than the typical acute respiratory distress syndrome (ARDS), patients with moderate or severe COVID-19 also develop a distinctive systemic coagulopathy, known as COVID-19-associated coagulopathy (CAC), which is different from sepsis-related forms of disseminated intravascular coagulation (DIC). Endotheliopathy or endotheliitis are other unique features of CAC. The endothelial cell perturbation can further increase the risk of thrombotic events in COVID-19 patients. In this review, we will summarize the current knowledge on COVID-19 coagulopathy and the possible mechanisms for the condition. We also discuss the results of clinical trials testing methods for mitigating thrombosis events in COVID-19 patients.

Effect of therapeutic versus prophylactic anticoagulation therapy on clinical outcomes in COVID-19 patients: a systematic review with an updated meta-analysis

Background

Previous studies demonstrate a reduced risk of thrombosis and mortality with anticoagulant treatment in patients with COVID-19 than in those without anticoagulation treatment. However, an open question regarding the efficacy and safety of therapeutic anticoagulation (T-AC) versus a lower dose, prophylaxis anticoagulation (P-AC) in COVID-19 patients is still controversial.

Methods

We systematically reviewed currently available randomized clinical trials (RCTs) and observational studies (OBs) from January 8, 2019, to January 8, 2022, and compared prophylactic and therapeutic anticoagulant treatment in COVID-19 patients. The primary outcomes were risk of mortality, major bleeding, and the secondary outcomes included venous and arterial thromboembolism. Subgroup analysis was also performed between critically ill and non-critically ill patients with COVID-19 and between patients with higher and lower levels of D-dimer. Sensitivity analysis was performed to decrease the bias and the impact of population heterogeneity.

Results

We identified 11 RCTs and 17 OBs fulfilling our inclusion criteria. In the RCTs analyses, there was no statistically significant difference in the relative risk of mortality between COVID-19 patients with T-AC treatment and those treated with P-AC (RR 0.95, 95% CI, 0.78–1.15, P = 0.60). Similar results were also found in the OBs analyses (RR 1.21, 95% CI, 0.98–1.49, P = 0.08). The pooling meta-analysis using a random-effects model combined with effect sizes showed that in the RCTs and OBs analyses, patients with COVID-19 who received T-AC treatment had a significantly higher relative risk of the major bleeding event than those with P-AC treatment in COVID-19 patients (RCTs: RR 1.76, 95% CI, 1.19–2.62, P = 0.005; OBs: RR 2.39, 95% CI, 1.56–3.68, P < 0.0001). Compared with P-AC treatment in COVID-19 patients, patients with T-AC treatment significantly reduced the incidence of venous thromboembolism (RR 0.51, 95% CI, 0.39–0.67, P<0.00001), but it is not associated with arterial thrombosis events (RR 0.97, 95% CI, 0.66–1.42, P = 0.87). The subgroup analysis of OBs shows that the mortality risk significantly reduces in critically ill COVID-19 patients treated with T-AC compared with those with P-AC treatment (RR 0.58, 95% CI, 0.39–0.86, P = 0.007), while the mortality risk significantly increases in non-critically ill COVID-19 patients treated with T-AC (RR 1.56, 95% CI, 1.34–1.80, P < 0.00001). In addition, T-AC treatment does not reduce the risk of mortality in COVID-19 patients with high d-dimer levels in RCTs. Finally, the overall sensitivity analysis after excluding two RCTs studies remains consistent with the previous results.

Conclusions

In our integrated analysis of included RCTs and OBs, there is no significant difference between the mortality of T-AC and P-AC treatment in unselected patients with COVID-19. T-AC treatment in COVID-19 patients significantly reduced the incidence of venous thromboembolism but showed a higher risk of bleeding than those with P-AC treatment. In addition, P-AC treatment was superior to T-AC treatment in non-critically ill COVID-19 patients, the evidence supporting the necessity for T-AC treatment in critically ill COVID-19 patients came only from OBs.

Trial registration

Protocol registration: The protocol was registered at PROSPERO (CRD42021293294).

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12959-022-00408-9.

The cross-talk of lung and heart complications in COVID-19: Endothelial cells dysfunction, thrombosis, and treatment

The pandemic respiratory illness SARS-CoV-2 has increasingly been shown to be a systemic disease that can also have profound impacts on the cardiovascular system. Although associated cardiopulmonary sequelae can persist after infection, the link between viral infection and these complications remains unclear. There is now a recognized link between endothelial cell dysfunction and thrombosis. Its role in stimulating platelet activation and thrombotic inflammation has been widely reported. However, the procoagulant role of microparticles (MPs) in COVID-19 seems to have been neglected. As membrane vesicles released after cell injury or apoptosis, MPs exert procoagulant activity mainly by exposing phosphatidylserine (PS) on their lipid membranes. It can provide a catalytic surface for the assembly of the prothrombinase complex. Therefore, inhibiting PS externalization is a potential therapeutic strategy. In this paper, we describe the pathophysiological mechanism by which SARS-CoV-2 induces lung and heart complications through injury of endothelial cells, emphasizing the procoagulant effect of MPs and PS, and demonstrate the importance of early antithrombotic therapy. In addition, we will detail the mechanisms underlying hypoxia, another serious pulmonary complication related to SARS-CoV-2-induced endothelial cells injury and discuss the use of oxygen therapy. In the case of SARS-CoV-2 infection, virus invades endothelial cells through direct infection, hypoxia, imbalance of the RAAS, and cytokine storm. These factors cause endothelial cells to release MPs, form MPs storm, and eventually lead to thrombosis. This, in turn, accelerates hypoxia and cytokine storms, forming a positive feedback loop. Given the important role of thrombosis in the disease, early antithrombotic therapy is an important tool for COVID-19. It may maintain normal blood circulation, accelerating the clearance of viruses, waning the formation of MPs storm, and avoiding disease progression.

The role of platelets, neutrophils and endothelium in COVID-19 infection

INTRODUCTION

COVID-19 is associated to an increased risk of thrombosis, as a result of a complex process that involves the activation of vascular and circulating cells, the release of soluble inflammatory and thrombotic mediators and blood clotting activation.

AREAS COVERED

This article reviews the pathophysiological role of platelets, neutrophils and the endothelium, and of their interactions, in the thrombotic complications of COVID-19 patients, and the current and future therapeutic approaches targeting these cell types.

EXPERT OPINION

Virus-induced platelet, neutrophil and endothelial cell changes are crucial triggers of the thrombotic complications and of the adverse evolution of COVID-19. Both the direct interaction with the virus and the associated cytokine storm concur to trigger cell activation in a classical thromboinflammatory vicious circle. Although heparin has proven to be an effective prophylactic and therapeutic weapon for the prevention and treatment of COVID-19-associated thrombosis, it acts downstream of the cascade of events triggered by SARS-CoV-2. The identification of specific molecular targets interrupting the thromboinflammatory cascade upstream, and more specifically acting either on the interaction of SARS-CoV-2 with blood and vascular cells or on the specific signalling mechanisms associated with their COVID-19-associated activation, might theoretically offer greater protection with potentially lesser side effects.

Cardiac megakaryocytes in SARS-CoV-2 positive autopsies

Thromboembolic phenomena are an important complication of infection by severe acute respiratory coronavirus 2 (SARS‐CoV‐2). Increasing focus on the management of the thrombotic complications of Coronavirus Disease 2019 (COVID‐19) has led to further investigation into the role of platelets, and their precursor cell, the megakaryocyte, during the disease course. Previously published postmortem evaluations of patients who succumbed to COVID‐19 have reported the presence of megakaryocytes in the cardiac microvasculature. Our series evaluated a cohort of autopsies performed on SARS‐CoV‐2‐positive patients in 2020 (n = 36) and prepandemic autopsies performed in early 2020 (n = 12) and selected to represent comorbidities common in cases of severe COVID‐19, in addition to infectious and noninfectious pulmonary disease and thromboembolic phenomena. Cases were assessed for the presence of cardiac megakaryocytes and correlated with the presence of pulmonary emboli and laboratory platelet parameters and inflammatory markers. Cardiac megakaryocytes were detected in 64% (23/36) of COVID‐19 autopsies, and 40% (5/12) prepandemic autopsies, with averages of 1.77 and 0.84 megakaryocytes per cm², respectively. Within the COVID‐19 cohort, autopsies with detected megakaryocytes had significantly higher platelet counts compared with cases throughout; other platelet parameters were not statistically significant between groups. Although studies have supported a role of platelets and megakaryocytes in the response to viral infections, including SARS‐CoV‐2, our findings suggest cardiac megakaryocytes may be representative of a nonspecific inflammatory response and are frequent in, but not exclusive to, COVID‐19 autopsies.

Quantifying the Excess Risk of Adverse COVID-19 Outcomes in Unvaccinated Individuals With Diabetes Mellitus, Hypertension, Ischaemic Heart Disease or Myocardial Injury: A Meta-Analysis

Background

More than 80% of individuals in low and middle-income countries (LMICs) are unvaccinated against coronavirus disease 2019 (COVID-19). In contrast, the greatest burden of cardiovascular disease is seen in LMIC populations. Hypertension (HTN), diabetes mellitus (DM), ischaemic heart disease (IHD) and myocardial injury have been variably associated with adverse COVID-19 outcomes. A systematic comparison of their impact on specific COVID-19 outcomes is lacking. We quantified the impact of DM, HTN, IHD and myocardial injury on six adverse COVID-19 outcomes: death, acute respiratory distress syndrome (ARDS), invasive mechanical ventilation (IMV), admission to intensive care (ITUadm), acute kidney injury (AKI) and severe COVID-19 disease (SCov), in an unvaccinated population.

Methodology

We included studies published between 1^st December 2019 and 16^th July 2020 with extractable data on patients ≥18 years of age with suspected or confirmed SARS-CoV-2 infection. Odds ratios (OR) for the association between DM, HTN, IHD and myocardial injury with each of six COVID-19 outcomes were measured.

Results

We included 110 studies comprising 48,809 COVID-19 patients. Myocardial injury had the strongest association for all six adverse COVID-19 outcomes [death: OR 8.85 95% CI (8.08–9.68), ARDS: 5.70 (4.48–7.24), IMV: 3.42 (2.92–4.01), ITUadm: 4.85 (3.94–6.05), AKI: 10.49 (6.55–16.78), SCov: 5.10 (4.26–6.05)]. HTN and DM were also significantly associated with death, ARDS, ITUadm, AKI and SCov. There was substantial heterogeneity in the results, partly explained by differences in age, gender, geographical region and recruitment period.

Conclusion

COVID-19 patients with myocardial injury are at substantially greater risk of death, severe disease and other adverse outcomes. Weaker, yet significant associations are present in patients with HTN, DM and IHD. Quantifying these associations is important for risk stratification, resource allocation and urgency in vaccinating these populations.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, registration no: CRD42020201435 and CRD42020201443.

Platelets in COVID-19 disease: friend, foe, or both?

Immuno-thrombosis of COVID-19 results in the activation of platelets and coagulopathy. Antiplatelet therapy has been widely used in COVID-19 patients to prevent thrombotic events. However, recent analysis of clinical trials does not support the major effects of antiplatelet therapy on mortality in hospitalized COVID-19 patients, despite the indisputable evidence for an increased risk of thrombotic complications in COVID-19 disease. This apparent paradox calls for an explanation. Platelets have an important role in sensing and orchestrating host response to infection, and several platelet functions related to host defense response not directly related to their well-known hemostatic function are emerging. In this paper, we aim to review the evidence supporting the notion that platelets have protective properties in maintaining endothelial barrier integrity in the course of an inflammatory response, and this role seems to be of particular importance in the lung. It might, thus, well be that the inhibition of platelet function, if affecting the protective aspect of platelet activity, might diminish clinical benefits resulting from the inhibition of the pro-thrombotic phenotype of platelets in immuno-thrombosis of COVID-19. A better understanding of the platelet-dependent mechanisms involved in the preservation of the endothelial barrier is necessary to design the antiplatelet therapeutic strategies that inhibit the pro-thrombotic activity of platelets without effects on the vaso-protective function of platelets safeguarding the pulmonary endothelial barrier during multicellular host defense in pulmonary circulation.