Nonsurgical placement of arterial endoprostheses: a new technique using nitinol wire.

Abstract

A new type of endovascular prosthesis has been developed using a unique metal alloy (nitinol) with a heat-sensitive memory. Nitinol wire coil grafts were straightened in ice water and passed into the canine aorta via catheter, where they reformed into their original shapes. Follow-up aortograms demonstrated long-term patency with minimal thrombus formation. Nitinol endovascular coil grafts may eventually be used in the nonsurgical treatment of several forms of vascular disease.

Stent Placement in Hemodialysis Access

“…Compared with stainless steel, nitinol stents do not shorten during placement. Nitinol is a nickel-titanium alloy with unique thermal recovery (commonly known as "smart metal") properties (53,54). If nitinol wire is initially formed into a desired shape and heated to 500 degrees Celsius, it will "memorize" that shape.…”

“…When cooled, the wire will become soft again and can be deformed without changing the "memorized" shape. If the straightened wire is then warmed to its transition temperature (usually body temperature for most alloys of nickel-titanium), it resumes its initially formed shape (53,54). This concept, "shape memory," is of particular importance in vascular access stenosis, since many of the lesions that need to be stented occur at the elbow or at tortuous intersections of veins.…”

A view of vascular stents.

“…"5 He later used stainless steel and then Nitinol coils in peripheral arteries of dogs with surprisingly good results.6,7 A number of stent designs by various investigators were developed thereafter, but each failed to maintain patency because of bulky and cumbersome profiles, unpredictable expansion, abrupt thrombosis, or gradual restenosis from intimal hyperplasia. [8][9][10][11][12] Three stent designs are currently under investigation for use in coronary arteries. The first is a spring-like design that can be constrained to a small diameter and then can be expanded to a predetermined dimension when the constraint is removed13 ( Figure 1A).…”

Charles Stent and the mystery behind the word “stent”

“…13 The word stent was used by Dotter and colleagues 7 in 1983 when they described a method involving percutaneous catheter placement of nitinol coil stents for restoring the patency of blood vessels and biliary tract. Simultaneously, Cragg et al 4 described a new type of endovascular prosthesis that involved nitinol wire coil grafts passed into canine thoracic aorta using a catheter, where they reformed into original shapes.…”