Background: The tendency of Dacron vascular grafts to expand after placement in the ascending and descending thoracic aorta has been noted, but never described in detail.
Methods: From 1986 to 2005, two or more computed tomography studies were obtained as part of routine postoperative surveillance in patients with Dacron grafts implanted to replace diseased aortic segments. Scans were digitized to evaluate the entire thoracic aorta. The median diameters of 547 grafts (18 to 34 mm) in the ascending (349) and descending (198) aorta were calculated from more than 2,000 postoperative computed tomography scans.
Results: In scans obtained 7 or fewer days after implantation, the median graft diameters increased from the manufacturer's measurement by 17% in the ascending aorta (n = 169; interquartile range, 11% to 21%; p < 0.0001) and 21% in the descending aorta (n = 63; interquartile range, 12% to 25%; p < 0.0001). From an initial scan within 30 days to at least one other within 18 months after implantation, ascending aorta grafts dilated further, at a median rate of 2.8% per year (n = 143; interquartile range, -2.2% to +6.9%; p = 0.0001). Descending grafts dilated less markedly: 1.1% per year (n = 80; interquartile range, -4.0% to +6.1%; p = 0.14). After 18 months, median graft expansion gradually diminished to less than 1% per year.
Conclusions: Significant initial expansion and early growth of woven vascular Dacron grafts occurs; it is slightly different in the ascending and descending aorta. Graft expansion should be anticipated when selecting grafts for aortic valve-sparing procedures to prevent development of regurgitation, and, for endoluminal repair of thoracoabdominal aneurysms, to prevent development of type III endoleaks in the projected landing zone.