Engineering goals for future thoracic endografts-how can we make them more effective?

Endovascular treatments for catastrophic aortic conditions have gained increasing popularity over the past 20 years. Originally developed for abdominal aortic aneurysms (EVAR), treatment has been modified for use in thoracic aortic repair (TEVAR). As expanding numbers of patients with increasingly intractable conditions and more hostile anatomies are treated, endovascular stent designs are maturing to be suitable for these more demanding situations. This article discusses the engineering considerations that apply to changing stent graft designs for current and evolving thoracic applications. The biological parameters that differentiate thoracic from abdominal aortic environments are outlined. Factors concerning materials, sealing mechanisms, deployment, stent frame architecture, and migration resistance are described, and eagerly awaited potential future developments are summarized.

INvestigation of STEnt grafts in patients with type B Aortic Dissection: design of the INSTEAD trial--a prospective, multicenter, European randomized trial.

PURPOSE: This study describes the design of an ongoing randomized trial initiated to compare the 2-year outcome of uncomplicated type B aortic dissection when treated by endovascular implantation of a Medtronic Talent stent graft adjunctive to best medical treatment versus best medical treatment alone. METHODS: Patients older than 18 years with type B aortic dissection as diagnosed by computed tomography or magnetic resonance angiography are randomized to either a thoracic aortic endoprosthesis and antihypertensive treatment, called "stent grafting," or a tailored antihypertensive treatment, called "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. RESULTS: 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 (>5 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 randomized and monitored for 24 months. CONCLUSIONS: The INSTEAD trial is the first randomized trial investigating the role of endoluminal treatment of uncomplicated type B aortic dissection. By the end of December 2004, 125 patients were randomized, accounting for 92% of the target. Final results of the INSTEAD trial should be available in 2006.

Device migration after endoluminal abdominal aortic aneurysm repair: analysis of 113 cases with a minimum follow-up period of 2 years.

PURPOSE: Device migration (DM) has been shown to cause late failure after endoluminal abdominal aortic aneurysm (AAA) repair. To establish the incidence rate and the predictive factors of distal migration of the proximal portion of the endograft, computed tomographic (CT) scans performed at different time intervals during follow-up examination of 113 patients were reviewed. PATIENTS AND METHODS: Between April 1997 and March 1999, 148 patients underwent endoluminal AAA repair with a modular endograft with infrarenal fixation (Medtronic-AVE AneuRx, Santa Rosa, Calif) at our unit. CT scans performed at 1, 6, and 12 months after surgery and yearly thereafter were prospectively stored in a computer imaging database. Patient demographics, risk factors, operative details, and follow-up events were prospectively collected. No patients were lost to follow-up examination. Twelve patients died within 2 years of surgery, four patients underwent immediate conversion to open repair, and adequate CT measurements were not feasible in 19 cases, which left 113 patients available for a minimum 2-year assessment and 418 CT scan results reviewed. Two vascular surgeons, blinded to patient identity and history with tested interobserver agreement (kappa = 0.64), separately reviewed axial reconstructions of CT scans. DM was defined as changes of 10 mm or more in the distance between the lower renal artery and the first visible portion of the endograft at follow-up examination. Ten possible independent predictors of DM were analyzed with multivariate Cox proportional hazards regression model. RESULTS: One AAA rupture, which was successfully treated, occurred at a mean follow-up period of 28 months (range, 24 to 46 months). Seventeen patients (15%) showed DM. Eight patients (47%) with DM underwent reintervention: a proximal cuff was positioned in six patients and late conversion to open repair was performed in two patients. Of the 10 variables analyzed with Cox proportional hazards regression model, AAA neck enlargement of more than 10% after endoluminal repair (hazard ratio, 7.3; confidence interval, 1.8 to 29.2; P =.004) and preoperative AAA diameter of 55 mm or more (hazard ratio, 4.5; confidence interval, 1.2 to 16.7; P =.02) were positive independent predictors of DM. The probability of DM at 36 months was 27% according to life table analysis. CONCLUSION: DM occurred in a significant portion of our patients, yet aggressive follow-up examination and a high reintervention rate prevented aneurysm-related death. According to our data, dilatation of the infrarenal aortic neck is an important factor that contributes to the distal migration of stent grafts, and patients with large aneurysms are at high risk for DM.

Outcome of abdominal aortic endografting in high-risk patients: a 4-year single-center study.

PURPOSE: To evaluate feasibility, safety, and effectiveness of endovascular abdominal aortic aneurysm (AAA) repair in patients whose fitness for surgery is questionable. METHODS: Between April 1997 and December 2001, 389 consecutive patients underwent endovascular AAA repair. Of these, 51 (13.1%) were ASA grade IV. The perioperative and late outcomes of this group were compared to the remaining 338 patients with ASA grades 0.05). Actuarial survival at 30 months was 62.9% in ASA IV group and 88.0% in ASA