Changes In Blood, Not Heart Could Be The Cause Of Cardiac Thrombosis In COVID Patients
Autopsy tissue samples of hearts from people who died early in the COVID-19 epidemic were investigated by a team of researchers. The American Journal of Pathology published the study. Blood clots (thromboses) were identified frequently and in large numbers within heart vessels, as expected, but there were no alterations in the endothelial cells lining the heart that are typical of thromboses. Instead, evidence suggested that activated neutrophils, a type of white blood cell, were the main source of hypercoagulability in the blood.
"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," explained lead investigator Jordan S. Pober, MD, PhD, Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA.
"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," he said.
COVID Patients Are At A Higher Risk Of Myocardial Injury
Patients with SARS-CoV-2 infection who are hospitalised have a higher risk of getting myocardial infarction. Despite indications of extensive virus presence in the lungs of patients who died from COVID-19, several studies have rarely discovered viral protein or RNA within the hearts of patients who died from COVID-19. The hearts of COVID-19 victims have been consistently characterized by thrombosis of micro and macro coronary arteries; however, the underlying reason is unknown.
According to the researchers, when compared to COVID-19-negative groups, thrombosis was the most common pathological finding in the COVID-19 group, with a significantly higher frequency of the microthrombi and a total number of macrothrombi. Despite the broad evidence of thrombosis, the COVID-19 group showed no signs of myocyte death or acute inflammation, which are both linked with myocardial infarction.
Alternations In Heart Vessel May Be The Primary Cause Of Cardiac Thrombosis
Endothelial cell damage, which can cause thrombosis by releasing microparticles carrying procoagulative tissue factor or by endothelial cell sloughing, which exposes platelet-activating collagen, was investigated in the heart vessels. The researchers were unable to discover such endothelial alterations in thrombosis sites. Instead, they discovered that four of the six COVID-19 patients had cardiac thrombi that contained neutrophils that showed procoagulant alterations in the blood, such as histone citrullination and the creation of neutrophil extracellular traps (NETs). NETS that appear to be directly connected with platelets have been seen in some photos. In the COVID-19 group, neutrophil-rich macrothrombi with 30% or more neutrophils were prevalent, but not in control tissue specimens.