Dr Barry Kevane
Consultant Haematologist, Mater Misericordiae University Hospital & Ireland East Hospital Group and Haematology Association of Ireland
The COVID-19 pandemic has presented the global healthcare community with unprecedented challenges. One such challenge has been the dramatically increased risk of blood clots observed among infected patients.
Venous thromboembolism (VTE) is the term used to describe the formation of harmful blood clots within the circulation. These occur most commonly in the limb veins or lungs. Thrombosis occasionally occurs within the brain and abdomen.
Preventing VTE-related mortality
VTE has long been recognised as being a major cause of cardiovascular mortality. Fortunately, the appropriate use of anti-clotting medicines has been shown to reduce the risk of death associated with blood clots among high-risk individuals (including hospitalised patients).
Increased VTE risk in COVID-19
Worryingly, an early trend which was observed in this pandemic was that VTE appeared to be occurring at very high rates among infected patients, despite the use of these anti-clotting medicines.
Moreover, a link between the severity of the COVID-19 illness and activation of blood clotting has been reported (based on laboratory findings), with high levels of clotting activation markers in the blood appearing to be predictive of poor outcomes and death.
Clinical trials of VTE treatment
These observations have sparked massive efforts to better understand the link between this infection and clotting as well as to improve our ability to prevent and treat these blood clots. A number of large, global studies are currently underway aiming to investigate whether intensified anti-clotting treatment may be required in COVID-19.
The Mater Hospital in Dublin has been the sole European recruitment site for one such study (The RAPID COVID COAG Trial). Results of these studies are expected this year, however preliminary results reported from similar clinical trials in recent months suggest that this treatment option may be of significant benefit to certain groups of patients with COVID-19 – not only in preventing VTE, but also in reducing risk of death and requirement for intensive care.
Given the limited treatments for this infection, these trials may provide significant hope for new options to improve outcomes, and the final results are eagerly awaited.
COVID-19 vaccines and thrombosis
The risk of thrombosis associated with certain COVID-19 vaccines has gained significant attention in recent months. In particular, unusual cases of cerebral thrombosis have been reported, although are extremely rare. Our understanding of this rare complication of vaccination is evolving but in the face of the significant risk of blood clotting and death due to a COVID-19 illness, it remains the firm recommendation of the healthcare community that individuals should accept the offer of a vaccine.