Coil

2. device originally designed by Gianturco and Wallace (Gianturco - Wallace coils, GWC) for permanent occlusion of major arteries. The devices have been used mainly for preoperative embolization of renal cell carcinomas and bleeding tumours. To increase thrombogenicity dacron fibres have been attached to the coils inducing a more rapid thrombosis (Fig.1). The principle indications for these spring coils are obliteration of large arteriovenous fistulae, occlusion of medium sized and large vessels after trauma, preoperative embolization of hypervascular tumours (renal cell carcinoma), aneurysms, pulmonary arteriovenous malformations, and obliteration of oesophageal varices. The GWC-coils are usually made from stainless steel and come in sizes of 320 mm. They may be introduced through standard angiographic catheters with a 0.035 or 0.038 inch inner lumen and are pushed through the delivery catheter by means of a guide wire.

For more peripheral and particularly super-selective embolization, microcoils made from platinum wire have been developed (Fig.2). They can be pushed through 2.2F coaxial catheters. Platinum wires are highly thrombogenic, radiopaque and biocompatible. They come in simple and complex shapes with and without silk or synthetic fibres to increase their thrombogenicity. They are nonferromagnetic and therefore do not disturb magnetic resonance investigations. Platinum microcoils are available commercially in straight, curled and complex helical forms. The non-neuroradiological indications for these platinum microcoils are growing, particularly for small peripheral arteriovenous fistulae and gastrointestinal bleeding.

To overcome the disadvantage that with conventional pushing technique for coil delivery only forward movement is possible, new delivery systems with detachable coils have been proposed. In the Jackson system (Cook Inc.) coils with synthetic fibres are connected to the delivery wire by a special spiral junction which can be loosened by turning the wire with a handle. Other systems using electrolysis or a laserbeam for coil detachment have been tried mainly in embolization of cerebral aneurysms.

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