DALLAS — Most patients who present with type A acute aortic dissection have an aortic diameter below the threshold at which preventive aneurysm surgery is recommended in current surgical guidelines, Dr. Linda A. Pape said at the annual scientific sessions of the American Heart Association.
“We have the problem of diameter not appearing to be a very good predictor of dissection risk,” observed Dr. Pape of the University of Massachusetts, Worcester.
She reported on 591 patients with type A acute aortic dissection enrolled in the International Registry of Acute Aortic Dissection. The registry, founded in the mid-1990s, includes 21 centers in 11 countries that have pooled resources to learn more about this disorder. All patients had measurements of their aortic diameter at dissection via MRI, transesophageal echo, CT, and/or angiography.
Current guidelines recommend preventive surgery when the maximum ascending aortic diameter reaches 5.5 cm in patients without Marfan syndrome and 5 cm in those with Marfan. That's the threshold at which the risk of dissection or rupture becomes sufficient to outweigh the morbidity of major surgery.
But in the first-ever study of its kind to examine the issue in a large unselected patient population, Dr. Pape found 59% of patients had a maximum ascending aortic diameter less than the 5.5-cm cutoff. “A surprisingly high 40% of patients dissected at diameters less than 5 cm,” the cardiologist added.
Patients who dissected at less than 5.5 cm had higher rates of reported back pain, radiating pain, abrupt onset of pain, and more neurologic deficits than did patients with an aortic diameter of 5.5 cm or greater at dissection, but rates of such complaints were high in both groups. Interestingly, the 5% of patients with Marfan syndrome were more likely to present with a diameter greater than 5.5 cm.
Overall, mortality in the study was 27%.
“Aortic size is not a sufficient marker of risk for dissection. In order to prevent aortic dissection and its potentially catastrophic outcome, we need better methods—genetic, biomarkers, or aortic functional studies—to identify patients at risk,” Dr. Pape said. These findings contribute to the rapidly evolving field of endovascular aneurysm repair.