Stent grafts in type B aortic dissection – study reports negative results
The INvestigation of STEnt Grafts in Aortic Dissection (INSTEAD) Trial, (Circulation. 2009;120:2519-2528) a randomized comparison of strategies for Type B aortic dissection found that thoracic endovascular aortic repair (TEVAR) failed to improve 2-year survival and adverse event rates in spite of favorable aortic remodeling. An accompanying editorial in Circulation (Circulation. 2009;120:2513-2514), while commenting that this trial has provided level 1 evidence, raised a concern that the negative result could be because the study was underpowered to evaluate the mortality end point. The study needed 28 events to have an adequate power while only 11 events were observed. The study randomized 140 persons with type B aortic dissection which was stable for at least 2 weeks into stent grafting vs optimal medical treatment strategies. The primary end point was all cause mortality at 2 years while secondary end points were aorta related death, progression (needing conversion or additional endovascular or open surgery) and aortic remodeling. In the TEVAR group there was 1 paraplegia, 1 stroke and 1 transient paraparesis while there was one paraparesis in the medical treatment group. Aortic remodeling with recovery of true lumen and thrombosis of thoracic false lumen occurred in 91.3% of TEVAR vs 19.4% in medical treatment group (P<0.001). There was no difference in the aorta related death rate nor was there any difference in the risk of the combined end point of aorta related death (due to rupture) and progression, including the need for further procedures.