A titanium-nickel alloy intravascular endoprosthesis. In vitro studies

In order to evaluate the implantation technique and reliability of conversion at different temperatures, a miniaturized intravascular endoprosthesis (IVEP) composed of thermal shape-memory effect TiNi alloy was delivered via a catheter into a 37 degrees C water mock circulatory loop (MCL) with a flow of 100 ml/min. The 2.5 mm diameter wire coil IVEP was torsion reduced to 1.4 mm, mounted on a modified balloon angioplasty catheter, and delivered into the MCL. Shape-memory conversion was activated thermally by injecting normal saline (3, 5, or 10 ml) at 45 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees, or 70 degrees C, while the local temperature (Tp) at the endoprosthesis site was monitored by a thermocouple. Inconsistent completed conversions of the IVEP were produced by injecting 10 ml of 60 degrees C, or 5 ml of 65 degrees C normal saline, which raised the Tp to 45 degrees to 53 degrees C. Complete conversion of the IVEP to 2.5 mm was produced consistently by injecting 10 ml of 65 degrees C or 5 ml of 70 degrees C saline, which raised Tp to 55 degrees C for less than 1 sec. This moderate Tp (55 degrees C) for such a short duration was shown to be a reliable method for remote conversion of the IVEP after catheter delivery. Knowledge of the minimum temperature and volume for consistent, complete conversion of the IVEP has permitted simple, safe conversion during in vivo studies. Delivery after balloon angioplasty is envisioned to either treat acute dissection with occlusion or to prevent chronic restenosis, in order to further improve the safety and efficacy of balloon angioplasty procedures.