In Vivo Assessment of Ascending and Arch Aortic Compliance.

Background: Dynamic compliance (Cd) of the adult thoracic ascending and arch aorta has had limited in vivo evaluation in patients with aortic disease. This study evaluates aortic compliance using intravascular ultrasound (IVUS) across a range of thoracic aortic diseases.

Methods: Seventy-nine patients undergoing thoracic aortic endovascular procedures had Cd measurements of the ascending aorta proximal to the origin of the brachiocephalic trunk and distal to the origin of the left common carotid artery using IVUS before endograft deployment. Cd was calculated for each segment using the following equation, Cd = ΔD/(D • ΔP) where ΔD = change in aortic diameter, D = diameter in diastole, and ΔP = pulse pressure.

Results: Mean Cd of the ascending aorta in all patients (18.4%/mm Hg) and aortic arch (16.5 %/100 mm Hg) did not differ significantly. Compliance was significantly lower in patients being treated for thoracic aortic aneurysm and penetrating ulcer than in patients with traumatic rupture, acute and chronic dissection (P = 0.009). Compliance was significantly higher in patients with aortic transection compared with thoracic aneurysm or penetrating ulcer (P = 0.001). Compliance decreased with age by 0.44 ± 0.06 (P = 0.001) per year in the ascending aorta and 0.41 ± 0.05 (P = 0.001) per year in the aortic arch. Compliance did not increase with diameter when adjusted for age (P = 0.65). Compliance measured in the ascending aorta in 7 patients after descending thoracic aortic endograft repair decreased to 12.6%/100 mm Hg, although not significant (P = 0.18).

Conclusions: Ascending and aortic arch compliance is significantly higher than reported for peripheral vessels. Thoracic aortic compliance decreases with age and is not related to aortic diameter. The results of the present study are important when considering the development of endoprosthesis devices and long-term effects on the thoracic aorta.