INSTEAD study for type B aortic dissection completes enrolment

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The multi-centre Investigation of Stent grafts in patients with type B Aortic Dissection (INSTEAD) study has completed enrolment. The study is the first prospective randomised thoracic clinical study, comparing the outcomes of patients treated for aortic dissection with the Medtronic Thoracic Talent Stent Graft System against outcomes for patients managed only with conventional anti-hypertensive treatment. The study involves 136 patients with type B aortic dissections, and is taking place at 11 clinical sites in four European countries – Austria, Germany, France and Italy.

The thoracic aorta rises from the heart (ascending aorta) and curves downward (aortic arch) before it descends into the abdominal cavity. Type B dissections typically occur when an inner wall of the descending segment separates from the outer layer and tears, allowing blood to pass into the elastic middle layer, creating a false channel that interferes with normal blood flow. This can lead to a rupture, which is often fatal.

Each year in Europe, an estimated 50,000 patients are diagnosed with lesions of the thoracic aorta, including those caused by Type B dissections. Many of these patients also have serious co-morbidities such as coronary artery disease, emphysema, high blood pressure or diabetes. These conditions make it difficult, if not impossible, for them to survive open surgical repair, which has been the standard of care. For those patients, considered ineligible for open surgical repair, conservative anti-hypertensive medical management, or “watchful waiting,” is often used as a treatment option. The objective of the INSTEAD study is to evaluate the clinical performance, safety and effectiveness of stent grafts in uncomplicated, type B dissections, and determine how this course of treatment compares to conventional treatment.

Professor Christoph A Nienaber, Head of the Division of Cardiology and Internal Medicine Department, Rostock University, Germany and principal investigator of the INSTEAD study, said, “The use of Talent endografts was compared to traditional best medical treatment with two years of follow up. The concept of aortic repair is working and appears promising in suitable anatomy. However, the data outcomes are currently being analysed and will be presented within the next year.”

The Talent Thoracic Stent Graft is introduced through a small opening in the femoral artery of the leg and advanced under fluoroscopic guidance to the site of the thoracic aortic aneurysm or dissection, where it is then deployed. Once in place, the stent graft expands to fit within the diameter of the aorta, thereby excluding the aneurysm or the false lumen, by providing a new path for blood. The Talent Thoracic Stent Graft, which has been available in Europe since 1998, is the market leading thoracic stent graft with over 16,000 implants worldwide.

Patients older than 18 years with type B aortic dissection as diagnosed by computed tomography or magnetic resonance angiography are randomised to either a thoracic aortic endoprosthesis and antihypertensive treatment, called bstent grafting or a tailored antihypertensive treatment, called best medical treatment. Only patients in a clinically stable condition and without spontaneous thrombosis of the false lumen after 14 days of the index dissection are considered eligible for study inclusion.

Primary outcome measure is all-cause mortality. Secondary outcome variables include conversion to stent and/or surgery, induced thrombosis of the false lumen, cardiovascular morbidity, aortic expansion (N5 mm/y of maximum diameter including true and false lumina), quality of life, and length of intensive care unit and hospital stay. The study design calls for 136 patients to be randomised and monitored for 24 months. Final results of the INSTEAD trial should be available in 2006.

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