PARIS – The usual rule that the larger an aortic aneurysm grows the greater the risk it will undergo dissection or rupture doesn’t work in patients with giant-cell arteritis. Their aortic aneurysms appear liable to dissect or rupture at any size after the diagnosis of giant-cell arteritis occurs, based on a retrospective study of 195 patients followed at a single U.S. center.

"Aortic size at diagnosis or last follow-up did not predict aortic dissection or rupture," Dr. Ashima Makol reported at the annual European Congress of Rheumatology, nor were linear, serial measurements of aortic size able to reliably predict risk for these complications in patients with GCA. Without a reliable way to identify patients with GCA at risk for dissection or rupture, the only management advice remaining is to follow GCA patients annually with imaging, said Dr. Makol, a rheumatologist at the Mayo Clinic in Rochester, Minn.

Positron emission tomography, CT angiography, or MR angiography seem to be the best ways to follow these patients, but if those are too costly to do annually, then transesophageal echocardiography or a chest x-ray are other options, Dr. Makol said in an interview.

Although 30% of patients with GCA have a vasculitis that involves the aorta and its branches and an increased risk for developing aortic aneurysms, the way these aneurysms change over time and the relationship between aneurysm size and the risk for dissection or rupture in GCA patients were not previously reported. To address this, Dr. Makol and her associates reviewed 195 patients with GCA and an aortic aneurysm seen at the Mayo Clinic during 2000-2012.

The aneurysms occurred in the ascending thoracic aorta in 161 patients (83%), the descending thoracic aorta in 21 (11%), and the abdominal aorta in the remaining 13 patients (7%). (Percentages total 101% because of rounding.) The patients averaged 74 years old, 62% were women, and 49% had a history of smoking.

During follow-up, 14 patients (7%) had an aneurysm dissection, and 1 patient (1%) had an aneurysm rupture, the investigators reported. All of the dissections and the rupture occurred in thoracic aorta aneurysms.

At the time of GCA diagnosis, the average aneurysm size in the 15 patients who developed an aneurysm complication was 51 mm, which was very similar to the average size of 49 mm in the 180 patients who did not have an aneurysm dissection or rupture during follow-up.

Patients also showed no clear link between aneurysm size at the time of dissection or rupture and the aneurysm size during follow-up of patients without these complications. The average maximum aneurysm diameter among the 15 patients with a complication at the time of their event was 54 mm, while the average aneurysm size at last follow-up among those without a dissection or rupture during follow-up was 50 mm, a difference that was not statistically significant, Dr. Makol said.

The average rate of aneurysm growth during 3 years of follow-up for all the GCA patients in the analysis was 1.59 mm/year, a rate "somewhat higher" than the average annual growth rate of 1 mm/year reported for aortic aneurysms in patients without inflammatory disease. The 54-mm average aneurysm diameter at the time of dissection or rupture in the CGA patients was "somewhat lower" than the 65-mm average aneurysm diameter seen at the time of dissection or rupture in patients without inflammatory disease, she noted.

Several patients in the series Dr. Makol reviewed who had no aneurysm complications had undergone prophylactic aneurysm repair. Clinicians at the Mayo Clinic follow the usual recommendations, which call for repair of aortic aneurysms when they reach at least 55 mm in diameter in men and 50 mm in women, and repair of thoracic aortic aneurysms that reach at least 55 mm in men and women. Prophylactic repair is also recommended for patients with an aneurysm that grows by more than 5 mm/year or causes symptoms. Many of the GCA patients included in the review therefore did not qualify for repair based on these criteria at the time of their GCA diagnosis or during follow-up. For now, no recommendations suggest that aortic aneurysms in patients in GCA need a different repair approach than patients without inflammatory disease.

The study is the first reported to look at the pattern of aneurysm growth and complications in GCA patients, although it is limited to the retrospective experience at one tertiary referral center and so may reflect a referral bias, Dr. Makol said. But the inability of the analysis to identify aneurysm characteristics in GCA patients that can telegraph an increased risk for complications means that all GCA patients with an aortic aneurysm need careful surveillance by annual imaging, she advised.

Dr. Makol said that she had no disclosures.

*6/24/14: This story was updated.

mzoler@frontlinemedcom.com

On Twitter @mitchelzoler

Giant-cell arteritis patients face high aortic aneurysm dissection risk