An experimental study on thrombogenicity of various metallic microcoils with or without thrombogenic coatings

RATIONALE AND OBJECTIVES. Various metallic microcoils have been used as effective embolic materials (stainless steel, tungsten, and platinum). It also has been reported in several articles that the thrombogenicity of coils increased after soaking in thrombin solutions. To compare the thrombogenicity, the authors performed in vitro study, measuring whole blood clotting time (WBCT) of the various microcoils with and without coating with thrombin, gelatin, or both gelatin and thrombin. METHODS. Stainless steel, tungsten, and platinum microcoils were used in the study. For thrombin coating, the microcoils were soaked in 4 U/mL thrombin solution for 5 minutes, dried for 30 minutes, then soaked and dried again. For gelatin coating, the microcoils were soaked in 10% gelatin solution for 15 minutes, dried for 30 minutes, then soaked and dried again. For dual coating with both gelatin and thrombin, they were soaked in 10% gelatin solution first for 15 minutes, dried for 45 minutes, and soaked in 4 U/mL thrombin solution for 5 minutes, and dried. The authors introduced 1 mt of fresh blood immediately into the test tube containing the microcoil, and measured the time taken for complete coagulation of the 1 mt blood (WBCT). RESULTS. Untreated stainless steel, tungsten, and platinum microcoils reduced WBCT from 15.76 minutes to 7.15, 5.64, and 7.27 minutes, respectively. Stainless steel microcoils after soaking in thrombin, gelatin, and both gelatin and thrombin solutions showed WBCT of 5.77, 5.82, and 4.44 minutes, respectively. Tungsten microcoils after soaking in thrombin, gelatin, and both gelatin, and thrombin solutions showed WBCT of 3.25, 4.95, and 3.67 minutes, respectively, Platinum microcoils after soaking in thrombin, gelatin, and both gelatin and thrombin solutions showed WBCT of 5.70, 10.01, and 6.27 minutes, respectively. CONCLUSIONS. Untreated tungsten microcoils showed superior clot promoting activity compared with untreated stainless steel and platinum microcoils. Clot promoting activity of microcoils was increased after coating with thrombin, or both gelatin and thrombin compared with untreated microcoils.