Predicting Death Risk After a Torn Aorta

A new study proposes an original way to predict post-hospital death risk for aortic dissection patients, and a new model for the mechanism behind that risk.

Researchers at the University of Michigan (U-M; Ann Arbor, USA) cardiovascular center conducted a study that involved data from 201 patients with aortic dissections in their descending aortas, who survived to hospital discharge and were followed for up to three years or until their deaths as part of IRAD, the International Registry of Acute Aortic Dissection.

The study focused on a phenomenon called the "false lumen,” created when the presence of blood clots causes the layers of the aorta to separate, like an onion. The false lumen runs alongside the "true” lumen, the aorta. As blood enters the false lumen from the top of the tear in the aorta, it gets trapped inside the new channel. Often, small openings at the bottom of the newly formed channel will allow the blood to flow out. But if the openings are not large enough, blood flow inside the false lumen is slowed down, pressure increases, and clots begin to form.

The study shows that the risk of post-hospital death is more than two-and-a-half times greater for patients who experience partial clotting (thrombosis) of the false lumen, than for those whose false lumen is clear of clots, or "patent.” Patients whose false lumen is totally filled with clotted blood, an infrequent event, have an intermediate risk of death. The study was published in the July 26, 2007, issue of the New England Journal of Medicine (NEJM).

"It appears that this may be a new predictor of which patients are most at risk--knowledge that might help guide decisions about when it's wise to proceed with more aggressive treatment and when we can hold off,” said lead author Thomas Tsai, M.D., M.Sc., a U-M fellow in cardiovascular medicine. But more research is needed.

In addition to the IRAD data, the researchers are studying a false lumen model of aortic dissection using an artificial material that simulates conditions inside the aorta.
Data suggest that in a partially thrombosed false lumen, the systolic blood pressure (BP) is lower than the systolic pressure in the aorta, but that the diastolic pressure is higher--leading to a higher average (mean) pressure in the false lumen as compared to the BP in patients with either a patent or a completely thrombosed false lumen.


Related Links:
University of Michigan