Coarctation of the aorta (CoA) is a congenital abnormality producing obstruction to blood flow through the aorta. CoA can occur in isolation, in association with bicuspid aortic valve, or with major cardiac malformations. CoA accounts for 5-8% of the 8/1000 (4-6/10,000) children born with congenital heart disease. Most CoA is newly diagnosed in childhood;<25% of these patients are recognized beyond 10 years of age. CoA is mostly repaired in childhood by surgery or alternatively by balloon catheter dilation. Recurrence rates range from 5-10%. Recurrence is often not recognized until adolescence or beyond. In the US and Europe, catheter-delivered balloon expandable stents have become the predominant therapy for CoA recurrence and new diagnoses of CoA in this age group;however, there are no FDA approved stents for use in the aorta. Large diameter biliary stents are currently used off label for this procedure. Enrollment into the pivotal trial of bare metal Cheatham Platinum Stents (CPS) for use in CoA is ongoing. The Coarctation of the Aorta Stent Trial (COAST) aims to confirm safety and efficacy of the CPS for untreated and recurrent CoA and achieve FDA approval for this indication. Approval of bare metal CPS will help treat patients who have this condition, but there are conditions that place some patients at high risk of aortic wall injury during bare metal stenting. Extreme narrowing, genetic aortic wall weakness, and advanced age are examples of conditions that place patients at risk of injury during bare metal stenting. Patients may also present with aortic wall injury (aneurysm) related to a prior CoA repair. Recurrence after surgical repair of CoA is 3-4% and following balloon dilation of CoA is 6-20%. Repair of such aneurysms is surgically challenging. For these patients, use of fabric-covered Cheatham Platinum Stents to either prevent or repair aortic wall injury has become the treatment of choice in Europe and recently in the USA through FDA-approved Compassionate Use of the Covered CPS. There are no alternative devices available in the US. This proposed trial will test safety and efficacy of Covered CPS to repair or prevent aortic wall injury associated with CoA. There are no prior surgical or catheterization trials describing outcomes for this therapy and thus, no basis for comparison. A single outcome assessment will not suffice since patients might receive a device for either indication. Thus, a three-category Severity of Illness Scale (SIS) was developed for this trial, based on the clinical judgment of a panel of pediatric cardiologists. It was reviewed by the COAST Data and Safety Monitoring Board (DSMB) and FDA's Office of Device Evaluation. The three illness categories include: 1) Level of upper extremity blood pressure, 2) Degree of upper to lower extremity pressure difference, and 3) Severity of aortic wall injury. Five levels of severity have been defined and will be used to assign level of illness in each of the three categories. The DSMB will assign a level of severity for each patient at baseline and one year follow-up for comparison. Improvement by at least one level has been designed to indicate clinical importance. Safety is evaluated by identifying adverse events and comparing their occurrence to that for surgical repair of uncomplicated CoA in similar age groups as reported in the medical literature.
Relevance Aneurysms of the aortic wall can occur in association with a narrowing of the aorta, called Coarctation of the Aorta, many years after corrective surgery or even during catheterization to dilate such a narrowing. Metallic stents with a thin, but impervious covering can provide life-saving treatment for these aortic wall injuries, but are not yet available for use in the United States. This project is designed to demonstrate benefit and safety of such a covered stent for use in this uncommon, but lifethreatening clinical condition.
