In vitro and in vivo Studies of the Extent of Electrothrombotic Deposition of Blood Elements on the Surface of Electrolytically Detachable Coils

Abstract

<jats:p> Endovascular treatment of intracranial aneurysms with electrolytically detachable coils is often claimed to be based on electrothrombosis, i.e. intra-aneurysmal thrombus formation through applied direct current. Despite the fact that this concept was described more than a century ago, the significance of electrothrombosis in the endovascular treatment of aneurysms remains debatable. Apart from electrothrombosis, mechanical obliteration of the aneurysmal lumen might be one of the many possible mechanisms to explain why and how detachable coils are effective in preventing aneurysms from (re-)rupture. The purpose of this experimental study was to investigate to what extent direct current comparable to that used for coil detachment would influence the adhesion of cellular and liquid blood components to the surface of electrolytically detachable platinum coils. </jats:p><jats:p> For the in vitro study, electrolytically detachable platinum coils of various types were exposed to stagnant heparinised blood for a total of 16 h, without or with applied direct current for 30 or 90 s (1 mA, 4–6 V, coil as anode). For the in vivo study, electrolytically detachable platinum coils were exposed to flowing blood for 180 s, without or with applied direct current (2 mA, 4–6 V, coil as either anode or cathode), without anti-coagulation and after intravenous administration of 5000 U Heparin and again after the intravenous administration of 500 mg Aspisol in addition to Heparin. After exposure to blood according to these different experimental protocols, the coils were fixed in formalin solution, gold coated and examined by scanning electron microscopy. </jats:p><jats:p> Thrombus formation on the surface of all unfibred coils was thin and highly variable both from coil to coil, and on different areas of any given coil. The application of direct current minimally enhanced thrombus formation in stagnant blood in vitro, but not in vivo. The cellular and fibrin adhesions on the coil surfaces without and with applied current did not effectively increase the diameter or volume of unfibred coils. Coils with attached nylon fibres, however, proved to be highly thrombogenic without or with application of current. In fibred coils, surface adhesions without and with applied current were voluminous enough to effectively increase the diameter of the coil, potentially important for the process of endosaccular aneurysm occlusion. </jats:p><jats:p> Electrothrombosis plays no role in the endovascular treatment of intracranial aneurysms with electrolytically detachable coils. This explains why platinum coils with non-electrolytic detachment mechanisms show a similar efficiency and recurrence rate. </jats:p>

In-vitro Assessments of Clot Elicitation by Thrombogenic Fibers vs. Embolization Coils

“…The metal spire serves as a support structure for the fibered material with no or insignificant effect on blood clotting. 28–31 Scanning Electron Microscopy image analyses (Figure 1) showed that the FDC used in this study bear multi-filament fibers in 30 localized clusters (plumes) of 24 to 27 individual filaments, with each individual filament presenting a length of 2375 ± 154 µm.…”

A review of technological innovations leading to modern endovascular brain aneurysm treatment

“…Later study would confirm that the therapeutic benefit of coiling was achieved due to the space-filling of coils as platinum coils with non-electrolytic detachment had similar rates of efficacy and recurrence (24). Potential mechanisms for preventing aneurysm rupture include slowing flow of blood in and out of the aneurysm to promote clot formation and subsequent intimal growth, as well as other mechanical effects such as flow diversion or biological interaction of the coils with the aneurysm wall.…”

Anticoagulation in Neurointerventions

“…electrothrombosis, which is no longer thought to be a relevant therapeutic contribution during detachment of Guglielmi detachable coils (GDC), can produce small thrombi which adhere to the coil, pusher or microcatheter and may be the source of a significant thrombus [22]. the surgical microscope images documented by Han et al [22] are striking although the significance of the phenomenon has been called into question by other authors [23]. in the last few years a variety of different coil detachment systems has been established in which electrothrombosis does not occur, such as electrical detachment in the case of the new target coils from Stryker (Boston Scientific Fremont, CA, USa) or the v-trak system of Microvention (Microvention, Tustin, CA, USA) and mechanical detachment of ev3 Axium (ev3, Irvine, CA, USA) coils.…”