March 2001

From University of Michigan Health System

Study: Ripped aortas kill often, but new knowledge may aid survival

Orlando, FL - 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, or 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 above 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, surprisingly, 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 the type of dissection nor 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 the awful truths and glimmers of hope that 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, M.D., a clinical assistant professor of cardiology in the UMHS Cardiovascular Center and an IRAD investigator.

While tears in the lining of the body's largest blood vessel are rare, occurring in 5,000 to 10,000 patients a year, they have long been known to be deadly. Without emergency attention and treatment - and even, often with it - the torn lining can continue to rip, block blood flow to the body, cause the heart to fail, or make the aorta swell into an aneurysm or even rip open.

In fact, aortic dissections are the leading cause of death among people with Marfan syndrome, a genetic disorder that weakens the aorta and produces unusually long limbs or other abnormalities in more than 100,000 Americans.

People with other heart valve and aorta problems, high blood pressure or a family history of aortic dissections are also at risk. Some people with aortic dissection can achieve a stable state with their condition, at least for a while, but most cases are acute and must be treated quickly.

Aortic dissection's symptoms, such as rapid onset of chest pain, sharp drops in blood pressure, altered consciousness, and limb paralysis, often mimic those of other cardiovascular conditions - resulting in delayed diagnosis. Only when patients reach an emergency room and undergo tests and scans can the cause be spotted. According to UMHS cardiology professor and ACC presenter William Armstrong, the two best imaging techniques for finding a dissection are computed tomography, or CT, and the more specialized transesophageal echocardiography.

After diagnosis, the ER staff may decide to send the patient to a hospital with the specialized staff and equipment to handle the condition - such as UMHS and the other IRAD hospitals. In fact, 67 percent of patients in the study were transferred to the IRAD hospital that treated them.

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 though 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 those patients over 65 years old, 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 those patients over 70, who represent a large and growing group. The IRAD team found that these elderly patients were more likely 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.

UMHS presentations at ACC 2001 involving IRAD data:

3/18, 8 a.m. Kim Eagle, State-of-the-Art Lecture: Diagnosis and Management of Aortic Dissection, in Session 42: Aortic Dissection

3/18, 8 a.m. William Armstrong, Key Echocardiography Information from the International Registry of Aortic Dissection, in Session 58, Transesophageal Echocardiography

3/18, 12 p.m. Rajendra Mehta, Acute Aortic Dissection in the Elderly: Clinical Characteristics, Management, and Outcomes in the Current Era, in Session 1045: Cardiovascular Disease in the Elderly: Prevalence, Physiology, Outcomes

3/18, 3 p.m. Rajendra Mehta, Predicting In-Hospital Mortality in Acute Type A Aortic Dissection: Lessons From the International Registry of Aortic Dissection, in Moderated Poster Session 1002: Outcomes Research in Cardiac Surgery

3/21, 8 a.m. various UMHS researchers (co-authors with other IRAD investigators), Mortality in Type B Acute Aortic Dissections in the Current Era: Results From the International Registry of Aortic Dissection and Percutaneous Therapeutic Procedures in Acute Aortic Dissection: Evidence for Benefit is Mounting in Session 1280: Outcomes Research in Special Populations: Arrhythmias, Syncope, and Aortic Dissection

This article comes from Science Blog. Copyright 2004

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