Background:Intravascular ultrasound (IVUS) examination can provide useful information during endovascular stent graft repair.However,its actual clinical utility in thoracic endovascular aortic repair (TEVAR) for type B aortic dissection (type B-AD) remains unclear,especially in complicated aortic dissection.We evaluated the effect of IVUS as a complementary tool during TEVAR.Methods:From September 2011 to April 2012,we conducted a prospective cohort study of 47 consecutive patients with complicated type B-AD diagnosed.We divided the patients into two groups:IVUS-assisted TEVAR group and TEVAR using angiography alone group.The general procedure of TEVAR was performed.We evaluated the perioperative and follow-up events.Patient demographics,comorbidities,preoperative images,dissection morphology,details of operative strategy,intraoperative events,and postoperative course were recorded.Results:A total of 47 patients receiving TEVAR were enrolled.Among them (females,8.51％;mean age,57.38 ± 13.02 years),13 cases (27.66％) were selected in the IVUS-assisted TEVAR group,and 34 were selected in the TEVAR group.All patients were symptomatic.The average diameter values of IVUS measurements in the landing zone were greater than those estimated by computed tomography angiography (31.82 ± 4.21 mm vs.30.64 ± 4.13 mm,P ＜ 0.001).The technique success rate was 100％.Among the postoperative outcomes,statistical differences were only observed between the IVUS-assisted TEVAR group and TEVAR group for total operative time and the amount of contrast used (P =0.013 and P ＜ 0.001,respectively).The follow-up ranged from 15 to 36 months for the IVUS-assisted TEVAR group and from 10 to 35 months for the TEVAR group (P =0.646).The primary endpoints were no statistical difference in the two groups.Conclusions:Intraoperative IVUS-assisted TEVAR is clinically feasible and safe.For the endovascular repair ofcomplicated type B-AD,IVUS may be helpful for understanding dissection morphology and decrease the operative time and the amount of contrast used.