New research highlights blood clot dangers of COVID-19

A special report published in the journal Radiology highlights the risk of COVID-19 blood clot complications and offers guidance for prevention, diagnosis, and treatment.

Blood clots and COVID-19

The report suggests that small vessel blood clot processes may play a role in respiratory failure in patients with COVID-19.

Clinicians worldwide face this new severe infectious lung disease with no proven treatment or cure. Based on recent reports that demonstrated a strong association between elevated D-dimer levels -- a protein found in the blood due to blood clots -- and poor prognosis, concerns have risen about blood clot complications in patients with COVID-19. Additionally, two studies from France found blood clots in the lungs of 23-30% of COVID-19 patients.

The National Institute for Public Health of the Netherlands asked a group of radiology and vascular medicine experts, including CVS's Professor Edwin van Beek, to provide guidance for the imaging processing and treatment of these important complications. Their report summarizes evidence for connections between COVID-19 and thromboembolic (blood clot) disease, while also outlining potential diagnostic and preventive actions that can be taken.

Worldwide, COVID-19 is being treated as a primary pulmonary [lung] disease. From the analysis of all available current medical, laboratory and imaging data on COVID-19, it became clear that symptoms and diagnostic tests could not be explained by impaired pulmonary ventilation alone.

Edwin J.R. van Beek, M.D., Ph.D.
Director at Edinburgh Imaging, Queens Medical Research Institute, University of Edinburgh

Recent observations suggest that respiratory failure in COVID-19 is not driven by the development of the acute respiratory distress syndrome alone, but that small vessel blood clot processes may play a role.

This may have important consequences for the diagnostic and treatment of these patients. There is a strong association between D-dimer levels, disease progression, and chest CT features suggesting blood clots within veins. In addition, various studies in patients with COVID-19 have shown a very strong association between increased D-dimer levels and severe disease/poor prognosis.

Diagnosis and Treatment

The report authors stress that careful attention needs to be paid to the initial diagnosis and treatment of patients at risk of or showing signs of blood clotting, which can occur in a substantial percentage of COVID-19 patients.

Imaging and pathological investigations confirmed the COVID-19 syndrome is a thrombo-inflammatory process that initially affects lung perfusion, but consecutively affects all organs of the body. This highly thrombotic syndrome leads to macro-thrombosis and embolism. Therefore, strict thrombosis prophylaxis, close laboratory and appropriate imaging monitoring with early anti-coagulant therapy in case of suspected venous thromboembolism are indicated.

Professor van Beek

Recommendations for diagnostic and treatment, which vary based on patient symptoms and risk profiles, include prophylactic-dose heparin (a blood thinner), chest CT, CT pulmonary angiography (an imaging test to see how the blood flows through the lung), and routine D-dimer testing.

Specific Links to Lung Embolism

Findings have also emerged linking COVID-19 more specifically with pulmonary embolism. A research letter from Hôpitaux Universitaires de Strasbourg published in Radiology reported that of 106 pulmonary CT angiograms performed for COVID-19 patients over a one-month period in a tertiary care center in France, 32 patients (30%) had acute pulmonary embolus (PE). This rate of PE is much higher than usually encountered in critically ill patients without COVID-19 infection (1.3%,) or in emergency department patients (3 to 10%). In the study, a D-dimer threshold of 2660 μg/L detected all patients with PE on chest CT.

A second research letter published today described a study from Centre Hospitalier Universitaire de Besancon in France pointed to high proportion (23%) of COVID-19 patients with contrast CT had PE. PE was diagnosed at mean of 12 days from symptom onset. Patients with PE were more likely require care in the critical care unit and to require mechanical ventilation. Lastly, a case report from Cooper University Hospital in Camden, New Jersey, describes multiple areas of pulmonary and arterial thrombosis in an 84-year-old man with COVID-19.

“COVID-19 is more than a lung infection. It affects the vasculature of the lungs and other organs and has a high thrombosis [blood clot] risk with acute life-threatening events that require adequate treatment with anticoagulants based on laboratory monitoring with appropriate imaging tests as required.

Professor van Beek

Related Links

Radiology Report

Edwin van Beek


Cover image credit: Blood clot in a vein. Annie CavanaghAttribution-NonCommercial 4.0 International (CC BY-NC 4.0)