Self-expandable and highly flexible nitinol stent: immediate and long-term results in dogs.

We sought to investigate the acute and long-term patency rates and the histologic response of coronary arteries to a self-expandable nitinol coil stent. Twenty-two stents were implanted. Angiographic patency was demonstrated acutely in all but one dog, in which the stent was released in a small branch (1 mm); mismatch in stent-to-artery diameters resulted in vessel closure. Two dogs died from anesthesia overdose and two from bleeding within 24 hours. All dogs were treated with aspirin (80 mg/day) and warfarin (2.5 mg/day) for up to 1 month. Sixteen dogs were monitored for 1 to 2 weeks, 1 month, 3 months, 6 months, and 1 year and underwent subsequent angiography and histopathologic examination. Angiographic artery dimensions measured immediately after stent implantation (2.72 +/- 0.4 mm) did not differ from those noted at follow-up (2.68 +/- 0.44 mm, p not significant). Histologic examination showed outward stent pressure compressing the internal elastic membrane and media in most cases. Intimal hyperplasia started at 2 weeks and was most apparent at 3 and 6 months. Mean intimal thickness was 30.7 +/- 10.9 mu, 141.8 +/- 105.4 mu, 227.1 +/- 104.1 mu, 211.8 +/- 99.1 mu, and 170.1 +/- 42.7 mu at 1 to 2 weeks and 1, 3, 6 and 12 months, respectively. Therefore the nitinol self-expandable stent provokes a moderate cellular proliferative response that reaches its maximum in 3 to 6 months without further progression.

Self-expandable Nitinol stent for cardiovascular applications: canine and human experience.

The initial experimental and clinical experience with the cardiovascular self-expandable Nitinol stent (vascular and coronary versions) is described. The stent is designed as a helical coil with two terminal balls that are used for restraining it on the delivery catheter. Upon release, the stent self-expands immediately. A temporary stent version continues with a long wire that can be removed by pulling it as a straight wire through a small profile catheter. The stent uncoils in its own groove upon removal, a relatively atraumatic procedure. The stents have been studied in dogs and in peripheral arteries in patients. The results show a transient nonocclusive proliferative response to the stent that is maximal at 3-6 mo. The removability of the permanent stent has been proven in dogs. The preliminary results in patients are encouraging and demonstrate its feasibility for permanent and potentially temporary arterial support.

A new self-expandable and removable metal stent for biliary obstruction--a preliminary report.

We report our experience with a new self expandable metallic stent, a coil spring made from a nickel-titanium alloy. The super elastic characteristic of this metal offers a very strong radial force and previous dilatation of biliary strictures is not necessary. The stent is endoscopically inserted constricted over an introducing catheter, expanding spontaneously after release to its original 8 mm diameter. During the last six months, eleven stents were inserted in nine patients with pancreatic carcinoma to relieve jaundice. Another stent was percutaneously implanted treating a benign stricture in a patient with a choledochojejunostomy after a Whipple operation. Clinical improvement was achieved in all the patients except in one who died from liver metastases 5 weeks later. In two patients, although stents were obstructed after 2 and 4 months from insertion, they were easily removed by pulling their distal end through the endoscopic working channel. After a mean follow up of 4.5 months, patients had no evidence of biliary reobstruction. Although follow-up is short, these results are encouraging, and this new metallic stent seems to have several advantages over the current commercially available ones.