Blood clots are common in the hearts of patients who die from COVID-19, researchers confirmed in a new analysis. However, the group noted, the changes expected to be seen in the endothelial cells lining those patients' hearts were absent. 

The team shared its findings in the American Journal of Pathology.

The study included autopsies of seven COVID-19 patients who died in the early stages of the pandemic, before anticoagulation treatment was routinely administered. There were four men and three women ranging in age from 50 to 94 years old. 

The researchers found that the likely cause of these blood clots was hypercoagulability caused by activated neutrophils.

“My laboratory has a long history of defining endothelial cell alterations that produce pathologies, including thrombosis, and we expected to confirm the widely held assumption that local endothelial cell alterations were responsible for thrombosis of the cardiac vessels in COVID-19 patients,” co-author Jordan S. Pober, MD, PhD, with the department of immunobiology at Yale University School of Medicine, said in a prepared statement. “Instead, we found that the cardiac thrombi contained neutrophils that expressed changes known to promote coagulation, including changes that are associated with cell death and inflammation.”