Observations on a small number of autopsied lung buttress reports from physicians treating covid-19 patients. Doctors described widespread damage to blood vessels and the presence of unexpected blood clots in a respiratory disease.
“What’s different about covid-19 is that the lungs do not get hard or are injured or destroyed before there is hypoxia,” the medical term for oxygen deprivation, said Steven J. Mentzer, a professor of operations at Harvard Medical School and part of the team who wrote the report. “For whatever reason, there is a vascular phase” in addition to the damage more often associated with viral diseases like influenza, he said.
The research team compared seven lungs of patients who died of covid-19, the disease caused by coronavirus, with lung tissue from seven patients who died of influenza-like pneumonia. They also examined 10 lungs that were donated for transplantation but were not used. The lungs, acquired in Europe, are matched by age and sex.
In the larger bloodstream of the lungs, the number of blood clots is similar in those of covid-19 and influenza patients, the researchers write. But in covid-19 patients, they found nine times as many micro-clots in small capillaries as small air sacs that allow oxygen to pass through the bloodstream and carbon dioxide to move. The virus could break down the walls of those capillaries and block the movement of those gases, the researchers write.
They also found inflammatory and damaged cells in the lining of blood vessels in covid-19 patients.
Most surprising is evidence that human lungs attacked by the SARS-CoV-2 virus have evolved new blood vessels.
“Lungs from patients with covid-19 have significant new vessel growth,” a finding described by the researchers as “unexpected.” In an interview, Mentzer predicted that it could be an attempt by the lungs to pass more oxygen to the hypoxic tissue.
“That may be one of the things that makes people better,” he said.
Researchers are looking for genetic and other variations that can help predict who is most susceptible to serious illnesses from the virus but find nothing in their small sample. So far in the pandemic, covid-19 has hit some groups, including older people, African Americans and people with underlying diseases like diabetes, the hardest.
“Patients who are well-behaved have respiratory disease, and patients who are having trouble also have a vascular component,” Mentzer said. But efforts to determine or explain who falls into each group have not been defeated, he said.