INSTEAD Trial Does Not Support TEVAR to Treat Type B Aortic Dissection

December 7, 2009—Christoph A. Nienaber, MD, et al have published results from the INSTEAD (Investigation of Stent Grafts in Patients With Type B Aortic Dissection) trial online ahead of print in Circulation.

The background of the study is that thoracic endovascular aortic repair (TEVAR) represents a novel concept for type B aortic dissection. Whereas TEVAR can be a life-saving approach in acute emergencies, the outcomes and survival of TEVAR in stable dissection are unknown.

As detailed in Circulation, 140 patients in stable clinical condition at least 2 weeks after index dissection were randomized to elective stent graft placement in addition to optimal medical therapy (n = 72) or to optimal medical therapy alone (n = 68) with surveillance (arterial pressure according to World Health Organization guidelines 120/80 mm Hg). The primary endpoint was all-cause death at 2 years. Secondary endpoints were aorta-related death, progression (with need for conversion or additional endovascular or open surgery), and aortic remodeling.

The investigators reported that there was no difference in all-cause deaths, with a 2-year cumulative survival rate of 95.6% ± 2.5% with optimal medical therapy versus 88.9% ± 3.7% with TEVAR (P = .15); however, the trial turned out to be underpowered. Moreover, the aorta-related death rate was not different (P = .44), and the risk for the combined endpoint of aorta-related death (rupture) and progression (including conversion or additional endovascular or open surgery) was similar (P = .65). Three neurological adverse events occurred in the TEVAR group (one paraplegia, one stroke, and one transient paraparesis) versus one case of paraparesis with the medical treatment group. Finally, aortic remodeling (with true lumen recovery and thoracic false lumen thrombosis) occurred in 91.3% of patients with TEVAR versus 19.4% of those who received medical treatment alone (P < .001), suggesting ongoing aortic remodeling.

The INSTEAD investigators concluded that in the first randomized study on elective stent graft placement in survivors of uncomplicated type B aortic dissection, TEVAR failed to improve 2-year survival and adverse event rates despite favorable aortic remodeling.