Patients with severe cases of Covid-19 had abnormal blood clotting, which contributed to some deaths, according to the research.
The study found that patients with higher levels of blood clotting had a significantly worse prognosis and were more likely to require intensive care.
Scientists at the Royal College of Surgeons in Ireland (RCSI) said their findings show that Covid-19 is associated with a unique type of blood clotting.
The study, carried out by RCSI's Irish Center for Vascular Biology (ICVB) and St James Hospital, Dublin, was published in the British Journal of Hematology.
The authors found that abnormal blood clotting occurred in patients with severe Covid-19 infection, causing micro-clots in the lungs.
Professor James O & # 39; Donnell, director of the ICVB, said: "Our new findings demonstrate that Covid-19 is associated with a unique type of blood clotting disorder that is mainly focused within the lungs and that, without a doubt, contributes to the high levels of mortality. observed in patients with Covid-19 ".
Donnell, a consultant hematologist at the National Coagulation Center at St. James Hospital, said that this scenario is not seen in other types of lung infection.
"In addition to the pneumonia that affects the small air sacs inside the lungs, we are also finding hundreds of small blood clots in the lungs," he added.
"This explains why blood oxygen levels drop dramatically in severe Covid-19 infection.
"Understanding how these micro-clots are being formed in the lung is essential for us to develop more effective treatments for our patients, especially those in high-risk groups.
"Further studies are needed to investigate whether different blood thinning treatments may play a role in selected high-risk patients in order to reduce the risk of clot formation."
Emerging evidence also shows that the abnormal blood clotting problem in Covid-19 results in a significantly increased risk of heart attacks and strokes.
& # 39; Donnell led the interdisciplinary study, with the first joint authors, Helen Fogarty and Liam Townsend, along with consultants from various specialties at St James & # 39; s Hospital and researchers from the University of Medicine and Health Sciences RCSI and Trinity College Dublin.
Further research will continue under the Irish Covid-19 Vasculopathy Study, which was jointly funded by the Health Research Board and Irish Research Council as part of the Irish government's Covid-19 Rapid Response Research funding.