Coronavirus (Covid-19)

A collection of articles and other resources on the Coronavirus (Covid-19) outbreak, including clinical reports, management guidelines, and commentary.


All Journal content related to the Covid-19 pandemic is freely available.

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Recent Randomized Trials of Antithrombotic Therapy for Patients With COVID-19

Authors: JACC State-of-the-Art ReviewAzita H. Talasaz, PharmD,a,bParham Sadeghipour, MD,cHessam Kakavand, PharmD,a,bMaryam Aghakouchakzadeh, PharmD,aElaheh Kordzadeh-Kermani, PharmD,aBenjamin W. Van Tassell, PharmD,d,eAzin Gheymati, PharmD,aHamid Ariannejad, MD,bSeyed Hossein Hosseini, PharmD,aSepehr Jamalkhani,cMichelle Sholzberg, MDCM, MSc,f,gManuel Monreal, MD, PhD,hDavid Jimenez, MD, PhD,iGregory Piazza, MD, MS,jSahil A. Parikh, MD,k,lAjay J. Kirtane, MD, SM,k,lJohn W. Eikelboom, MBBS,mJean M. Connors, MD,nBeverley J. Hunt, MD,oStavros V. Konstantinides, MD, PhD,p,qMary Cushman, MD, MSc,r,sJeffrey I. Weitz, MD,t,uGregg W. Stone, MD,k,vHarlan M. Krumholz, MD, SM,w,x,yGregory Y.H. Lip, MD,z,aaSamuel Z. Goldhaber, MD,j and Behnood Bikdeli, MD, MSj,k,w,∗


Endothelial injury and microvascular/macrovascular thrombosis are common pathophysiological features of coronavirus disease-2019 (COVID-19). However, the optimal thromboprophylactic regimens remain unknown across the spectrum of illness severity of COVID-19. A variety of antithrombotic agents, doses, and durations of therapy are being assessed in ongoing randomized controlled trials (RCTs) that focus on outpatients, hospitalized patients in medical wards, and patients critically ill with COVID-19. This paper provides a perspective of the ongoing or completed RCTs related to antithrombotic strategies used in COVID-19, the opportunities and challenges for the clinical trial enterprise, and areas of existing knowledge, as well as data gaps that may motivate the design of future RCTs.

Thromboembolism in Patients With Coronavirus Disease-2019

Microvascular and macrovascular thrombotic complications, including arterial and especially venous thromboembolism (VTE), seem to be common clinical manifestations of coronavirus disease-2019 (COVID-19), particularly among hospitalized and critically ill patients (1234). Pooled analyses have helped in providing aggregate estimates of thrombotic events (4,5). In a recent systematic review and meta-analysis, the overall incidence of VTE among inpatients with COVID-19 was estimated at 17% (95% confidence interval [CI]: 13.4 to 20.9), with variation based on study design and method of ascertainment; there was a four-fold higher incidence rate in patients in the intensive care units (ICUs) compared with non-ICU settings (28% vs. 7%) (6). In addition, postmortem studies show frequent evidence of microvascular thrombosis in patients with COVID-19 (7,8). The influence of these events on mortality rates remains unknown (9).Go to:

Pathophysiology of Thromboembolism in COVID-19: Virchow’s Triad in Action

COVID-19 can potentiate all 3 components of Virchow’s triad and increases the risk of thrombosis (Figure 1 ). First, severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection may trigger endothelial dysfunction. Using the angiotensin-converting enzyme 2, which is expressed on the surface of many cells, SARS-CoV-2 enters endothelial cells and may impair their intrinsic antithrombotic properties. It is proposed that viremia, hypoxia, the inflammatory response, increased expression of tissue factor, and elevated levels of neutrophil extracellular traps (NETs) can together disrupt the hemostasis equilibrium and promote endothelial activation (101112). This induction of a procoagulant state along with the reduction in plasminogen activators further results in increased platelet reactivity (131415). Inflammatory cytokines and endothelial activation can lead to downregulation of antithrombin and protein C expression. They can also lead to an increase in the levels of plasminogen activator inhibitor; fibrinogen; factors V, VII, VIII, and X; and von Willebrand factor (16). Increased platelet reactivity, NETosis, and alterations in the aforementioned hemostatic factors result in a hypercoagulable state (171819202122).

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COVID-19 vaccines and thrombosis with thrombocytopenia syndrome

Authors: Chih-Cheng Lai 1Wen-Chien Ko 2Chih-Jung Chen 3Po-Yen Chen 4Yhu-Chering Huang 3Ping-Ing Lee 5Po-Ren Hsueh 6 7


Introduction: To combat COVID-19, scientists all over the world have expedited the process of vaccine development. Although interim analyses of clinical trials have demonstrated the efficacy and safety of COVID-19 vaccines, a serious but rare adverse event, thrombosis with thrombocytopenia syndrome (TTS), has been reported following COVID-19 vaccination.

Areas covered: This review, using data from both peer-reviewed and non-peer-reviewed studies, aimed to provide updated information about the critical issue of COVID-19 vaccine-related TTS.

Expert opinion: : The exact epidemiological characteristics and possible pathogenesis of this adverse event remain unclear. Most cases of TTS developed in women within 2 weeks of the first dose of vaccine on the receipt of the ChAdOx1 nCoV-19 and Ad26.COV2.S vaccines. In countries with mass vaccination against COVID-19, clinicians should be aware of the relevant clinical features of this rare adverse event and perform related laboratory and imaging studies for early diagnosis. Non-heparin anticoagulants, such as fondaparinux, argatroban, or a direct oral anticoagulant (e.g. apixaban or rivaroxaban) and intravenous immunoglobulins are recommended for the treatment of TTS. However, further studies are required to explore the underlying mechanisms of this rare clinical entity.

Plain language summary: What is the context? Thrombosis with thrombocytopenia syndrome (TTS) usually develops within 2 weeks of the first doses of the ChAdOx1 nCoV-19 and Ad26.COV2.S COVID-19 vaccines. TTS mainly occurs in patients aged < 55 years and is associated with high morbidity and mortality. What is new? TTS mimics autoimmune heparin-induced thrombocytopenia and can be mediated by platelet-activating antibodies against platelet factor 4. Non-heparin anticoagulants, such as fondaparinux, argatroban, or a direct oral anticoagulant (e.g. apixaban or rivaroxaban) should be considered as the treatment of choice if the platelet count is > 50 × 109/L and there is no serious bleeding. Intravenous immunoglobulins and glucocorticoids may help increase the platelet count within days and reduce the risk of hemorrhagic transformation when anticoagulation is initiated. What is the impact? TTS should be a serious concern during the implementation of mass COVID-19 vaccination, and patients should be educated about this complication along with its symptoms such as severe headache, blurred vision, seizure, severe and persistent abdominal pain, painful swelling of the lower leg, and chest pain or dyspnea. The incidence of TTS is low; therefore, maintenance of high vaccination coverage against COVID-19 should be continued.

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Anticoagulation in COVID-19: current concepts and controversies

  1. Authors: Chandra16289Uddalak Chakraborty2, Shrestha Ghosh1, Sugata Dasgupta3


Rising incidence of thromboembolism secondary to COVID-19 has become a global concern, with several surveys reporting increased mortality rates. Thrombogenic potential of the SARS-CoV-2 virus has been hypothesised to originate from its ability to produce an exaggerated inflammatory response leading to endothelial dysfunction. Anticoagulants have remained the primary modality of treatment of thromboembolism for decades. However, there is no universal consensus regarding the timing, dosage and duration of anticoagulation in COVID-19 as well as need for postdischarge prophylaxis. This article seeks to review the present guidelines and recommendations as well as the ongoing trials on use of anticoagulants in COVID-19, identify discrepancies between all these, and provide a comprehensive strategy regarding usage of these drugs in the current pandemic.

This article is made freely available for use in accordance with BMJ’s website terms and conditions for the duration of the covid-19 pandemic or until otherwise determined by BMJ. You may use, download and print the article for any lawful, non-commercial purpose (including text and data mining) provided that all copyright notices and trade marks are retained.


The novel beta-coronavirus, appropriately named SARS-CoV-2 by the International Committee of Taxonomy of Viruses, belongs to a family of single-stranded RNA viruses, members of which have been recognised as causative agents of the SARS-CoV and Middle East respiratory syndrome coronavirus outbreak in 2002 and 2012, respectively.1 2 Presently, the novel COVID-19 poses a major global health crisis, having been declared a pandemic on 11 March 2020 by the WHO.

Over the past several months, an overwhelming amount of literature suggests an increased risk of thromboembolic manifestations associated with COVID-19.2 Several hypotheses have been suggested to understand the underlying pathophysiology behind development of a prothrombotic state in COVID-19 such as exaggerated inflammatory response resulting in activation of the coagulation cascade and endothelial injury.3 4 Usage of anticoagulants in COVID-19 remains an area of conjecture with no definite guidelines published to date highlighting the timing, dosage and duration of anticoagulation as well as the drug of choice. Most internationally published guidelines, based on consensus statements and expert opinions, recommend therapeutic doses of heparin only in patients diagnosed with or highly suspected of developing macrothrombi such as pulmonary embolism (PE) or deep vein thrombosis (DVT). However, these guidelines including those by CHEST, rarely address the requirement of post discharge thromboprophylaxis.5

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Potential mechanisms of cerebrovascular diseases in COVID-19 patients

Authors: Manxue Lou 1Dezhi Yuan 2 3Shengtao Liao 4Linyan Tong 1Jinfang Li 5Affiliations expand


Since the outbreak of coronavirus disease 2019 (COVID-19) in 2019, it is gaining worldwide attention at the moment. Apart from respiratory manifestations, neurological dysfunction in COVID-19 patients, especially the occurrence of cerebrovascular diseases (CVD), has been intensively investigated. In this review, the effects of COVID-19 infection on CVD were summarized as follows: (I) angiotensin-converting enzyme 2 (ACE2) may be involved in the attack on vascular endothelial cells by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), leading to endothelial damage and increased subintimal inflammation, which are followed by hemorrhage or thrombosis; (II) SARS-CoV-2 could alter the expression/activity of ACE2, consequently resulting in the disruption of renin-angiotensin system which is associated with the occurrence and progression of atherosclerosis; (III) upregulation of neutrophil extracellular traps has been detected in COVID-19 patients, which is closely associated with immunothrombosis; (IV) the inflammatory cascade induced by SARS-CoV-2 often leads to hypercoagulability and promotes the formation and progress of atherosclerosis; (V) antiphospholipid antibodies are also detected in plasma of some severe cases, which aggravate the thrombosis through the formation of immune complexes; (VI) hyperglycemia in COVID-19 patients may trigger CVD by increasing oxidative stress and blood viscosity; (VII) the COVID-19 outbreak is a global emergency and causes psychological stress, which could be a potential risk factor of CVD as coagulation, and fibrinolysis may be affected. In this review, we aimed to further our understanding of CVD-associated COVID-19 infection, which could improve the therapeutic outcomes of patients. Personalized treatments should be offered to COVID-19 patients at greater risk for stroke in future clinical practice.

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High sensitivity troponin and COVID-19 outcomes

Authors: Nikolaos Papageorgiou,a,bCatrin Sohrabi,aDavid Prieto Merino,c,dAngelos Tyrlis,aAbed Elfattah Atieh,aBunny Saberwal,aWei-Yao Lim,aAntonio Creta,aMohammed Khanji,aReni Rusinova,aBashistraj Chooneea,aRaj Khiani,d,eNadeev Wijesuriya,e,fAnna Chow,e,fHaroun Butt,e,fStefan Browne,e,fNikhil Joshi,e,fJamie Kay,e,fSyed Ahsan,a and Rui Providenciaa,g



Recent reports have demonstrated high troponin levels in patients affected with COVID-19. In the present study, we aimed to determine the association between admission and peak troponin levels and COVID-19 outcomes.


This was an observational multi-ethnic multi-centre study in a UK cohort of 434 patients admitted and diagnosed COVID-19 positive, across six hospitals in London, UK during the second half of March 2020.


Myocardial injury, defined as positive troponin during admission was observed in 288 (66.4%) patients. Age (OR: 1.68 [1.49–1.88], p < .001), hypertension (OR: 1.81 [1.10–2.99], p = .020) and moderate chronic kidney disease (OR: 9.12 [95% CI: 4.24–19.64], p < .001) independently predicted myocardial injury. After adjustment, patients with positive peak troponin were more likely to need non-invasive and mechanical ventilation (OR: 2.40 [95% CI: 1.27–4.56], p = .007, and OR: 6.81 [95% CI: 3.40–13.62], p < .001, respectively) and urgent renal replacement therapy (OR: 4.14 [95% CI: 1.34–12.78], p = .013). With regards to events, and after adjustment, positive peak troponin levels were independently associated with acute kidney injury (OR: 6.76 [95% CI: 3.40–13.47], p < .001), venous thromboembolism (OR: 11.99 [95% CI: 3.20–44.88], p < .001), development of atrial fibrillation (OR: 10.66 [95% CI: 1.33–85.32], p = .026) and death during admission (OR: 2.40 [95% CI: 1.34–4.29], p = .003). Similar associations were observed for admission troponin. In addition, median length of stay in days was shorter for patients with negative troponin levels: 8 (5–13) negative, 14 (7–23) low-positive levels and 16 (10–23) high-positive (p < .001).


Admission and peak troponin appear to be predictors for cardiovascular and non-cardiovascular events and outcomes in COVID-19 patients, and their utilization may have an impact on patient management.

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Pathological findings in organs and tissues of patients with COVID-19: A systematic review

  1. Authors: Sasha Peiris, Hector Mesa, Agnes Aysola, Juan Manivel, Joao Toledo, Marcio Borges-Sa, Sylvain Aldighieri, Ludovic Reveiz



Coronavirus disease (COVID-19) is the pandemic caused by SARS-CoV-2 that has caused more than 2.2 million deaths worldwide. We summarize the reported pathologic findings on biopsy and autopsy in patients with severe/fatal COVID-19 and documented the presence and/or effect of SARS-CoV-2 in all organs.

Methods and findings

A systematic search of the PubMed, Embase, MedRxiv, Lilacs and Epistemonikos databases from January to August 2020 for all case reports and case series that reported histopathologic findings of COVID-19 infection at autopsy or tissue biopsy was performed. 603 COVID-19 cases from 75 of 451 screened studies met inclusion criteria. The most common pathologic findings were lungs: diffuse alveolar damage (DAD) (92%) and superimposed acute bronchopneumonia (27%); liver: hepatitis (21%), heart: myocarditis (11.4%). Vasculitis was common only in skin biopsies (25%). Microthrombi were described in the placenta (57.9%), lung (38%), kidney (20%), Central Nervous System (CNS) (18%), and gastrointestinal (GI) tract (2%). Injury of endothelial cells was common in the lung (18%) and heart (4%). Hemodynamic changes such as necrosis due to hypoxia/hypoperfusion, edema and congestion were common in kidney (53%), liver (48%), CNS (31%) and GI tract (18%). SARS-CoV-2 viral particles were demonstrated within organ-specific cells in the trachea, lung, liver, large intestine, kidney, CNS either by electron microscopy, immunofluorescence, or immunohistochemistry. Additional tissues were positive by Polymerase Chain Reaction (PCR) tests only. The included studies were from numerous countries, some were not peer reviewed, and some studies were performed by subspecialists, resulting in variable and inconsistent reporting or over statement of the reported findings.


The main pathologic findings of severe/fatal COVID-19 infection are DAD, changes related to coagulopathy and/or hemodynamic compromise. In addition, according to the observed organ damage myocarditis may be associated with sequelae.

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Late Complications of COVID-19; a Systematic Review of Current Evidence

Authors: SeyedAhmad SeyedAlinaghi,1Amir Masoud Afsahi,2Mehrzad MohsseniPour,1Farzane Behnezhad,3Mohammad Amin Salehi,1Alireza Barzegary,4Pegah Mirzapour,1Esmaeil Mehraeen,5,* and Omid Dadras6



COVID-19 is a new rapidly spreading epidemic. The symptoms of this disease could be diverse as the virus can affect any organ in the body of an infected person. This study aimed to investigate the available evidence for long-term complications of COVID-19.


This study was a systematic review of current evidence conducted in November 2020 to investigate probable late and long-term complications of COVID-19. We performed a systematic search, using the keywords, in online databases including PubMed, Scopus, Science Direct, Up to Date, and Web of Science, to find papers published from December 2019 to October 2020. Peer-reviewed original papers published in English, which met the eligibility criteria were included in the final report. Addressing non-human studies, unavailability of the full-text document, and duplicated results in databases, were characteristics that led to exclusion of the papers from review.


The full-texts of 65 articles have been reviewed. We identified 10 potential late complications of COVID-19. A review of studies showed that lung injuries (n=31), venous/arterial thrombosis (n=28), heart injuries (n=26), cardiac/brain stroke (n=23), and neurological injuries (n=20) are the most frequent late complications of COVID-19.

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Better Anticoagulated Than Not! Hypercoagulability in COVID-19

Authors: Dhauna P. Karam, MD1

Incidence of thrombotic complications in patients with COVID-19 who are critically ill is high, with an estimated incidence of 31% for arterial or venous thromboembolism (VTE), acute pulmonary embolism, ischemic stroke, and myocardial infarction. On the basis of the study by Klok et al,1 pulmonary embolism was the most common thrombotic complication in critically ill patients with COVID-19 despite being on standard anticoagulation. Prevention of thromboembolism with anticoagulants is recommended in all critically ill patients with COVID-19.

The American Society of Hematology (ASH) guideline panel (updated April 7, 2021) recommends prophylactic anticoagulation in all critically ill patients with COVID-19 without suspected or confirmed venous thromboembolism (VTE). ASH defines patients with COVID-19 critical illness as someone who is suffering from a life-threatening condition, typically admitted in an intensive care unit. It is recommended that individualized assessment of the patient’s thrombotic and bleeding risk needs to be performed before deciding on anticoagulation.2 What about hospitalized patients with COVID-19 who are not critically ill? What are some clinical parameters that can be used to guide decisions on anticoagulant use in such patients?

The accompanying manuscript by Gaddh et al3 reports guidelines used in a large academic institution, Emory University School of Medicine, Atlanta, Georgia, to determine anticoagulation in hospitalized patients with COVID-19. The guidelines were created by a multidisciplinary panel of experts and were incorporated into frontline care at Emory. The three-tiered algorithm was used to risk stratify patients admitted with a primary diagnosis of COVID-19. It was not recommended for use in patients incidentally found to have COVID-19 during hospitalization for other causes. On the basis of the guidelines, patients with normal D-dimer, no evidence of thromboembolism and not critically ill were given prophylactic anticoagulation (group 1). Patients with elevated D-dimer (> 6 times upper limit normal) with no evidence of thromboembolism and not critically ill were given intermediate-dose anticoagulation. Patients critically ill without any evidence of thromboembolism and without elevation of D-dimer were also given intermediate-dose anticoagulation. Patients with confirmed thromboembolism or those with other markers of possible thromboembolism (worsening hypoxia or pulmonary status without identifiable cause and limb edema) received therapeutic anticoagulation. Anticoagulation was continued for 1 week after discharge in group 1 patients. Group 2 received anticoagulation for 4-6 weeks after discharge. Finally, group 3 received anticoagulation for minimum 3 months postdischarge. Preliminary findings revealed low bleeding complications. Data on type of anticoagulant used, incidence of thromboembolism in the hospitalized group following the above guidelines, and improvement in morbidity and mortality rates were not provided. The algorithm is a simple, practical statement, which can guide frontline caregivers until evidence-based recommendations become available. Group 1 and 3 recommendations are supported by major organizational guidelines such as ASH and International Society on Thrombosis and Haemostasis (ISTH). Preliminary guidelines from these organizations refrain from commenting strongly on intermediate-dose anticoagulation in the absence of supporting data from clinical trials but do support anticoagulant dose escalation on the basis of clinician’s assessment for high-risk patients.2,4

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COVID-19 – A vascular disease

Authors: Hasan K. Siddiqi,a,bPeter Libby,a,⁎ and Paul M Ridkera,b


Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) leads to multi-system dysfunction with emerging evidence suggesting that SARS-CoV-2-mediated endothelial injury is an important effector of the virus. Potential therapies that address vascular system dysfunction and its sequelae may have an important role in treating SARS-CoV-2 infection and its long-lasting effects.

SARS-CoV-2 infection and vascular dysfunction

In health, the vascular endothelium maintains homeostasis through regulation of immune competence, inflammatory equilibrium, tight junctional barriers, hemodynamic stability as well as optimally balanced thrombotic and fibrinolytic pathways. In the novel coronavirus disease of 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), dysregulation of many of these pathways has emerged as a mediator of severe disease. The constellation of clinical and biomarker derangements seen in COVID-19 can be classified into disruption of the immune, renin-angiotensin-aldosterone (RAA), and thrombotic balance, all of which converge on the vascular endothelium as a common pathway. Accumulating evidence from basic science, imaging and clinical observations, has clarified the picture of COVID-19 as a vascular disease. Understanding the disease in this context may provide novel avenues of understanding COVID-19 and lead to critically needed improvements in therapeutic strategies.

SARS-CoV-2 uses the angiotensin converting enzyme 2 (ACE2) to facilitate entry into target cells and initiate infection. This viral entry into the cell is further mediated by transmembrane serine protease 2 (TMPRSS2) and cathepsin L which cleave the S protein on the viral particle to permit engagement with ACE2 [1]. Endothelial cells (ECs) in general and cardiac pericytes in particular express abundant ACE2, making them a direct target of SARS-CoV-2 infection (Fig. 1 ) [2]. Examination of the pulmonary vascular bed shows severe derangements in COVID-19, compared to control and influenza patients, particularly with widespread thrombosis and microangiopathy, endothelial activation and extensive angiogenesis [3]. These studies and pervasive findings establish the role of viral injury to the vascular system with resulting vascular dysfunction in COVID-19 patients [4].

Fig. 1

Open in a separate windowFig. 1

SARS-CoV-2 Induced Endothelial Injury

Legend: A schematic of SARS-CoV-2 infection and proposed resulting endothelial injury, involving immune activation, pro-thrombotic milieu, and RAAS dysregulation. These insults interact with each other to cause end-organ dysfunction that is manifest in many COVID-19 patients.

TMPRSS2 = Transmembrane protease serine 2; ADAM17 = A disintegrin and metalloproteinase 17; TNF = Tumor necrosis factor; TNFr = Tumor necrosis factor receptor; TLR = toll-like receptor; DAMPs = Damage-associated molecular patterns; PAMPs = Pathogen-associated molecular patterns; PAI-1 = plasminogen activator inhibitor-1; vWF = von Willebrand factor; eNOS = endothelial nitric oxide; tPA = tissue plasminogen activator; AT1R = angiotensin 1 receptor; ARDS = acute respiratory distress syndrome.

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