In vivo degradation of tungsten embolisation coils

It has been suggested that tungsten embolisation coils in intracranial aneurysms may dissolve in situ. These coils are also used, in much larger quantities, for the occlusion of larger vessels outside the cranium. This study was performed to investigate whether tungsten embolisation coils may become degraded in vivo and to examine whether this is radiographically evident on medium-term follow-up. 10 patients who had undergone aortic stent-graft repair of an abdominal aortic aneurysm (8 male and 2 female, mean age 69.7 years) and 10 age- and sex-matched controls were studied. The study group had also received an average of 64 cm of tungsten coil either to prevent or to treat an endoleak. Whole blood, serum and urine tungsten levels were assayed. Immediate post-operative and follow-up abdominal radiographs were reviewed by two consultant vascular radiologists to detect visible changes in the coils. Whole blood, serum and urine levels of tungsten were highly and significantly elevated (p < 0.001) in the study group compared with the controls. No radiographic changes in the coils were seen at an average of 16.7 months. In conclusion, tungsten embolisation coils dissolve in humans but radiographic changes are not apparent on medium-term follow-up. The clinical significance of these findings is uncertain but long-term follow-up is needed.