Coarctation of the Aorta Stent Trial (COAST): study design and rationale

Coarctation of the aorta (CoA) accounts for 4% to 5% of congenital cardiac abnormalities. Stent therapy has become an accepted alternative to surgery for older children and adults, although there are no balloon-expandable stents approved by the Food and Drug Administration for use in the aorta. The Cheatham-Platinum (CP) stent was designed for CoA therapy and is widely used outside the United States. We have designed the first prospective trial of stent therapy for CoA to serve as the pivotal trial for Food and Drug Administration approval of the CP stent.

The COAST study is a prospective, multicenter, single-arm clinical study. The population includes patients with native or recurrent CoA. Four primary outcome variables were defined. For each variable, the stent will be compared to performance guidelines derived from surgical experience. The first efficacy outcome is reduction in arm-leg systolic blood pressure gradient, and the second is reduction in hospital length of stay. Safety outcomes include the following: the occurrence of any serious or somewhat serious adverse event attributed to the stent or implantation procedure and the occurrence of postprocedure paradoxical hypertension. A total of 105 patients treated with the CP stent will be enrolled.

To ascertain the effectiveness and safety of an interventional device, randomized controlled trials have been offered as the criterion standard. However, these trials are not well suited to study rare conditions such as CoA, especially once the therapy in question has received acceptance within the medical community. New clinical trial and statistical approaches are needed to evaluate such therapies. The COAST study is an example of this kind of innovative trial design.