The value of intraoperative intravascular ultrasound for determining stent graft size (excluding abdominal aortic...

Since the introduction of endovascular stent grafts at our institution we have used intraoperative intravascular ultrasound (IVUS) to definitively determine stent graft size. In this study, expected stent graft size, based on preoperative helical CT scan measurements, was compared with the actual final size, based on intraoperative IVUS measurements. Between December 1996 and January 1998, 54 patients were treated with an AneuRxTM bifurcated stent graft. Preoperatively all patients underwent angiography and helical CT scanning. Expected stent graft size was determined according to these measurements. The final stent graft size was based on IVUS measurements acquired during the procedure. Differences in expected and final size were compared and follow-up endoleaks were also noted. Differences in diameter measurements between CT and IVUS were compared using the paired Student's t-test. Differences in expected and chosen stent graft length were compared using the McNemar's test for paired proportions of binomial outcomes. Our results showed that helical CT scanning overestimates diameter and underestimates length. This underestimation of length is explained by the tortuosity of the aorta and iliac arteries while using axial slices of the CT scan. The last-minute corrections based on the intraoperative IVUS measurements did not result in a high incidence of endoleaks at fixation zones. In our opinion, the possibility of making final corrections in the choice of diameter or length of the stent graft is the additional value of intraoperative IVUS.