The University Record, March 19, 2001

Study of aortic dissection data aims to improve patient care

By Kara Gavin
Health System Public Relations

It’s a terrifying prospect, and for good reason: A rip in the lining of your aorta can kill you swiftly and painfully if you don’t get skilled help—or even if you do. That bleak reality is the central conclusion from new results in a major international study of the phenomenon. But the data also seem to give some clues that could help cut the death toll.

In several talks and posters being presented at the annual Scientific Session of the American College of Cardiology, physicians are sharing new results from the largest-ever study of patients with torn aorta linings, or aortic dissection. The University of Michigan Health System is the coordinating center for the International Registry of Aortic Dissection (IRAD).

One startling finding: Nearly 33 percent of those struck by Type A aortic dissection died in the hospital, despite the high experience level of staff at the IRAD institutions. The toll was more than 50 percent in patients who didn’t or couldn’t have surgery to fix the tear at its origin near the heart.

The study also finds that the Type B form of dissection, considered less severe because it starts further from the heart, killed more than 11 percent of those it struck. And the data showed the elderly did poorly no matter what type of dissection they had or how it was treated.

But on the positive side, the study finds that it may be possible to help physicians predict quickly which patients need the most aggressive treatment. And other preliminary data suggest that minimally invasive techniques may help improve survival for those who can’t endure surgery.

The significance of the IRAD study stems both from the fact that it provides more data than ever on an uncommon, deadly phenomenon and from what the data show. The researchers, from 17 large institutions in six countries, hope their findings will help steer aortic dissection diagnosis and care and improve patients’ chances of survival.

“This large collection of recent data makes it possible for the first time to study aortic dissection care and outcomes in a way that will affect patient care,” says Rajendra Mehta, clinical assistant professor of cardiology in the Cardiovascular Center and an IRAD investigator.

The study looked prospectively and retrospectively at patients treated between 1995 and 1999, a recent enough period to reflect advances in diagnosis and care. The outcomes for patients treated with either surgical or medical (drug-based) care were examined.

For the 284 patients found to have Type B dissection, which occurs in the descending portion of the aorta at or below the first branch leading to the arms, the overall mortality of 11 percent was higher than expected. But the study doesn’t include enough data on how patients with different symptoms, risk factors and treatment fared to allow doctors to make an accurate model of patient survival that could guide future treatment of this type of dissection.

That kind of decision-making prediction, though, may indeed be possible for patients found to have Type A dissection, according to results presented by Mehta. The 474 patients with acute dissection whose rips occurred in the ascending part of the aorta, closest to the heart, were enough to determine which factors are most important in predicting mortality.

In the IRAD results, 80 percent of the acute Type A patients had emergency surgery, and although 26 percent of them died, that percentage was much lower than the 56 percent death rate in those who only received medications. The data also showed that patients over 65, those who had migrating chest pain, those who had extremely low blood pressure or pulse deficits and those who had neurologic deficits were more likely to die. From these findings, Mehta and his colleagues hope to guide doctors on which patients to treat most aggressively.

One group that deserves special attention is patients over 70, who represent a large and growing group. The IRAD team found that these patients were likelier to die in the hospital after either kind of aortic dissection than those under 70, even though they were about half as likely to have a Type A dissection. They were also much less likely to get aggressive, surgical treatment, perhaps because their other health risks made them less able to endure it.

Luckily for these patients and others, the IRAD data also show promise for minimally invasive approaches that can stop the dissection without opening the chest. Such percutaneous procedures, which use stents and scaffolds to shore up the torn area, seemed to give a better result than drug therapy in Type B dissection patients, according to preliminary IRAD data.