New hope for aortic dissection survivors

Published on July 26, 2007 at 2:15 PM · 2 Comments

Each year, 10,000 Americans suffer a sudden tear in the lining of their body's largest blood vessel, the aorta.

It's often misdiagnosed, and it can kill if not treated immediately. Actor John Ritter died of such a tear in 2003.

Better medical imaging and treatments such as medication, surgery and catheter-based procedures are now giving more patients a chance to survive this crisis, called aortic dissection. But once they leave the hospital, patients face a one-in-four chance of dying within a few years. And doctors don't have a reliable way of predicting who is most at risk of dying, and who might benefit most from surgery or other treatment.

Now, a study published in the July 26 New England Journal of Medicine by an international team of researchers may offer hope for aortic dissection survivors, and give guidance for their physicians. The researchers, led by University of Michigan Cardiovascular Center experts, propose a new way to predict post-hospital death risk for aortic dissection patients, and a new model for the mechanism behind that risk.

Their model focuses on a phenomenon that can easily be seen on modern medical-imaging scans: the presence of blood clots in the channel created when the layers of the aorta separate like two layers of an onion. This channel, called the “false lumen”, runs alongside the “true” lumen, which is the hollow middle area of the aorta that acts as the pipeline for blood to flow out of the heart and down through the abdomen.

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 aren't large, 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 — which happens quite infrequently — have an intermediate risk of death.

“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,” says lead author Thomas Tsai, MD, MSc, a U-M fellow in cardiovascular medicine. “But more research is needed.”

The study involves 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.

IRAD, which is headquartered at the U-M CVC and supported in part by the U-M Medical School, the Mardigian Foundation, and the Varbedian Fund for Aortic Research, includes data from 22 large medical centers in 11 countries. It pools data on treatment and patient outcomes for this relatively rare condition, to allow researchers to draw more scientific conclusions based on larger amounts of data than can be gathered at a single center.

Senior author Kim Eagle, M.D., FACC, is a primary IRAD investigator. He says, “I believe that we are beginning a new era of scientific discovery in aortic diseases at U-M and in IRAD. By taking advantage of advances in imaging studies and genetic associations of aortic diseases correlations with this entire care area will be transformed.” Eagle is the Albion Walter Hewlett Professor of Cardiovascular Medicine at U-M and a director of the U-M Cardiovascular Center.

In addition to the IRAD data, Tsai and colleagues at the U-M Biomedical Engineering School are studying a false lumen model of aortic dissection using an artificial material that simulates conditions inside the aorta.

Blood pressure within the false lumen, and the properties and responses of the torn aortic wall, may all play a role in the higher death risk that appears to be associated with partial thrombosis. Data suggest that in a partially thrombosed false lumen, the systolic pressure 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 false lumen in patients with a patent or completely thrombosed false lumen.

Tsai also notes that U-M interventional radiologist David Williams, M.D., has studied the false lumen, and that U-M vascular surgeon Ramon Berguer, M.D., has studied the dynamics of endoleaks in a similar model of abdominal aortic aneurysms treated with stent grafts -- and that this research and work by other researchers around the world lends further weight to the model proposed from the new data. Still, he says, only prospective research and other validation efforts will be able to tell if the false-lumen model is accurate.

The NEJM paper is based on retrospective clinical data from 114 patients who had a patent false lumen when they were admitted to an IRAD hospital, 68 patients who had a partially thrombosed (clot-filled) false lumen, and 19 who had a complete thrombosed false lumen.

By the end of the three-year follow-up period, nearly 25 percent of the patients had died. But the difference in death risk was striking: 13.7 percent of the patients with patent (clear) false lumens had died, compared with 31.6 percent of the partially thrombosed patients and 22.6 percent of the completely thrombosed patients. The difference held up after other factors were corrected for.

In addition to the importance of the false lumen, the researchers found that patients with a history of atherosclerosis and of aortic aneurysm were also more likely to die during the follow-up period. Aortic aneurysms are different from aortic dissections because they involve a bulge in the aorta formed by a weakened area of blood vessel, but the layers of the vessel wall stay together.

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Comments
  1. Lydia Chang Lydia Chang United States says:

    Your article is very informative.   I appreciate it.  My question is in the Quick Comment.
    My daughter is 65, had Aorta Dissection a year ago, March, 11.  She has survived, appeared quite well.   I don't live with her, only being told.  This year, she wanted to play
    SLOW TENNIS, with a trainer.  Is it dangerous and pre-maturely doing this?
    If you could give me some kind of answer,  I'd appreciate it.
    Thank you         Lydia Chang






































      

    • Greg R Greg R Canada says:

      I'm getting on 2 years since surgery. Mine happened Halloween night 2010. I find the biggest drawback to recovery is being around really negative people. We shouldn't be around them in normal life but after having a traumatic event like that, it's really hard to get thru the day. On the bright side I wasn't given much of a chance to live and yet here I am. If anyone else comes across this comment and has gone thru this or knows someone who has email me if you like. Here's to ya.   Greg

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