Guidewires

Percutaneous coronary intervention A minimally invasive procedure whereby access to the coronary arteries is obtained through the femoral artery up the aorta to the coronary os. Contrast media is used to visualize the coronary artery stenosis using a coronary angiogram. A guidewire is used to cross the stenosis and a small balloon is inflated and/or stent is deployed to break up atherosclerotic plaque and restore coronary artery blood flow. The stent is left in place to prevent acute closure and restenosis of the coronary artery. Newer stents are coated with antiproliferative drugs, such as paclitaxel and sirolimus, which further reduce the risk of restenosis of the coronary artery. 

Shape-memory alloys (e.g. Cu-Zn-Al, Fe-Ni-Al, Ti-Ni alloys) are already in use in biomedical applications such as cardiovascular stents, guidewires and orthodontic wires. The shape-memory effect of these materials is based on a martensitic phase transformation. Shape memory alloys, such as nickel-titanium, are used to provide increased protection against sources of (extreme) heat. A shape-memory alloy possesses different properties below and above the temperature at which it is activated. Below this temperature, the shape of the alloy is easily deformed due to its flexible structure. At the activation temperature, the alloy can be changed by applying a force, but the structure resists this deformation and returns back to its initial shape. The activation temperature is a function of the ratio of nickel to titanium in the alloy. In contrast with Ni-Ti, copper-zinc alloys are capable of a two-way activation, and therefore a reversible variation of the shape is possible, which is a necessary condition for protection purposes in textiles used to resist changeable weather conditions. 

Stiff guidewires with variable stiffness (3-12 gms) New devices... 

Frontrunner blunt microdissection catheter Radiofrequency ablation with optical Coherence reflectometry guidance Laser guidewire High frequency ultrasound... 

I 9 Strauss BH, Segev A, Wright GA, et al, Microvessels in chronic total occlusions pathways for successful guidewire crossing J Interv Cardiol 2005 18 425-436,... 

Since the first steps in transluminal balloon dilation of mitral valves in 1982 (24) numerous techniques have been described. One method is to access the left atrium with a transseptal puncture from the venous side (antegrade). Another way is to advance the catheter via the aorta into the left ventricle and perform the valvulotomy from the arterial side (retrograde). The use of two dilation balloons introduced via the transseptal approach is a common technique described by Bonhoeffer using a monorail-type system over a single guidewire (25). 

A guidewire and subsequently a balloon catheter (2.0-2.5 mm in diameter) are advanced into the septal perforator. Identification of the target territory is performed by contrast echocardiography to determine the most appropriate septal perforator for ethanol infusion by showing echo... 

Fig. 7. Schematic diagram of the canine femoral artery copper coil model of thrombolysis. A thrombogenic copper coil is advanced to either femoral artery via the left carotid artery. By virtue of the favorable anatomical angles of attachment, a hollow polyurethane catheter advanced down the left carotid artery nearly always enters the descending aorta, and with further advancement, into either femoral artery without fluoroscopic guidance. A flexible, Teflon-coated guidewire is then inserted through the hollow catheter and the latter is removed. A copper coil is then slipped over the guidewire and advanced to the femoral artery (see inset). Femoral artery flow velocity is measured directly and continuously with a Doppler flow probe placed just proximal to the thrombogenic coil and distal to a prominent sidebranch, which is left patent to dissipate any dead space between the coil and the next proximal sidebranch. Femoral artery blood flow declines progressively to total occlusion over the next 10-12 mm after coil insertion.

Despite the sophistication of today s medical devices, the materials used often result in undesirable complications, including bacterial infections, blood clots, tissue trauma due to device insertion, and friction and wear of implants. This is especially true for such devices as catheters, guidewires, stents, probes, and prosthetic implants. 

Exchange of catheter over guidewire Pharmacologic therapy... 

GRAM (28) 1998 104 STt <75 y CS included <24 h Multicenter GR II After culprit lesion crossed with guidewire 13 (25)... 

Zwolle (30) 1998 227 STt <6 h 6-12 h if ongoing ischemia Single center PS After guidewire or balloon induced reperfusion 15 (13)... 

Borenstein, J. (2000), The Omnimate A Guidewire- and Beacon-Free AGV for Highly Recon-figurable Apphcations, International Journal of Production Research, Vol. 38, No. 9, pp. 1993-2010. 

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