Triaxial coil embolization using Guglielmi detachable coils with the voltage-dependent coil-detaching technique

Introduction

A new microcatheter with a 1.9-Fr non-tapered tip has recently become available. It can be inserted into a 2.7-Fr microcatheter, which has a large inner diameter, and is commonly used when a better quality angiogram is desired. The usefulness of this new technique, the triple co-axial (triaxial) system, has been reported in transcatheter arterial chemoembolization (TACE) for hepatocellular carcinoma (HCC) (1,2). We recently began performing coil embolization with the triaxial system; however, the inner diameter of the 1.9-Fr. non-tapered microcatheter was so small that only a 0.012-inch or smaller coil could be inserted. Therefore, we attempted triaxial coil embolization using 0.010-inch Guglielmi detachable coils (GDCs). However, a two-tip marker microcatheter is required to detach a GDC, and the 1.9-Fr non-tapered microcatheter only has a one-tip marker. To solve this problem, we attempted to identify the detaching point by monitoring changes in the voltage of the GDC power supply, which we referred to as the voltage-dependent coil-detaching technique. The aim of this study was to describe this new technique and evaluate its technical feasibility and clinical efficacy.

Material and Methods

This study was approved by the Institutional Review Board, and written informed consent was obtained from each patient before the procedure. The procedure was performed in 20 patients, 15 men and five women, with a median age of 62 years (range, 37–89 years) between June 2011 and January 2013. The diagnoses that necessitated GDC embolization are summarized in Table 1. The indication of the procedure was decided based on computed tomography (CT), magnetic resonance imaging (MRI), endoscopy, and/or clinical findings. Eleven of the 20 procedures were emergency cases, while nine were elective. The hemodynamic situation was stable in 19 of the cases, while the vital signs of one emergency case were in a shock status. Medical records and imaging of the procedures were reviewed, and the technical success rate, clinical success rate, and complications of the procedure were evaluated. Technical success was defined as the successful delivery and detachment of a GDC, and clinical success was defined as the immediate postembolic complete cessation of blood flow confirmed by digital subtraction angiography. Complications associated with the procedure were evaluated with physical examinations and follow-up roentgenograms and/or CT.

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Table 1.

Diseases treated with triaxial coil embolization.

Disease	n
Gastrointestinal bleeding	5
Traumatic bleeding	3
Recanalization of pulmonary AVM	3
Pulmonary AVM	2
Postoperative bleeding	2
Type 2 endoleak after EVAR	2
Lumbar aneurysm	1
Recanalization of splenic aneurysm	1
Tumor-related bleeding	1
Total	20

Results

A total of 140 GDCs were used and 20 arteries were embolized. The diameter of the GDCs used in this procedure was in the range of 2–20 mm (median, 3 mm), and the number of the GDCs was in the range of 1–16 (median, 7) per procedure. The embolized artery was a branch of the gastrointestinal artery in six patients, a branch of the pulmonary artery in five, the feeding artery of a type II endoleak after endovascular abdominal aortic aneurysm repair (EVAR) in two, and other arteries in seven. The procedure was initially attempted with the conventional microcatheter in six patients and failed; therefore, it was exchanged to the triaxial system. Using the conventional microcatheter appeared to be too complicated in 14 patients because contrast-enhanced CT showed that the access route was long and/or tortuous. Therefore, the triaxial system was initially introduced.

Among the 140 GDCs, 131 were successfully delivered and deployed to the aimed position. Therefore, the technical success rate of the procedure was 94% (131/140). However, nine coils could not be successfully delivered. In six of nine failed cases, stacking of GDCs occurred inside the microcatheter, and an incorrect connection of a GDC cable occurred in three of nine failed cases. The complete cessation of blood flow was confirmed by digital subtraction angiography just after embolization in 19 of the 20 cases (Figs. 1 and 2). Thus, the clinical success rate was 95% (19/20). One patient in which the procedure failed was involved in a traffic accident, and had severe damage to the right femur and pelvis. The hemodynamic status of the patient was already in a shock-vital status when coil embolization was started, and the patient died during the procedure because of blood loss in spite of attempts to resuscitate him. The other 19 patients did well without recanalization after transarterial embolization, during a follow-up of 9–28 months (median, 20 months). No complications associated with this procedure, such as ischemia, another bleeding, or coil migration, were noted. OPEN IN VIEWER

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Fig. 2.

A 67-year-old man presented with intraperitoneal bleeding after total gastrectomy with distal pancreatosplenectomy for gastric cancer. (a) Angiography of the celiac artery showed extravasation from the common hepatic artery (arrow). Thus, coil embolization was performed from the distal site of extravasation to the proximal site using a conventional microcatheter, and 0.0135-inch and 0.018-inch coils. (b) Angiography of the celiac artery suggested the disappearance of extravasation. (c) However, angiography of the SMA showed extravasation (large arrow), which appeared to be from anastomosis of the gastroduodenal artery (GDA) (small arrows). Although we decided to perform coil embolization from the anastomosis, it was long and tortuous; therefore, we introduced the triaxial system and 0.010-inch GDCs. (d) Angiography showed the common hepatic artery selected from anastomosis of the GDA for the triaxial system (small arrow, 1.9-Fr. no-taper microcatheter; large arrow, 2.7-Fr. microcatheter). The 1.9-Fr. no-taper microcatheter was then inserted to the inside of the existing coils, and coil embolization was performed using nine GDCs (2 mm–1 cm × 3, 2.5 mm–2 cm × 1, 2.5 mm–3 cm × 3, 3 mm–8 cm × 1, 4 mm–4 cm × 1). (e) Angiography of the GDA after coil embolization showed the complete cessation of bleeding.

Discussion

Coil embolization is frequently performed in interventional radiology for conditions including bleeding, aneurysms, and arteriovenous malformations (AVMs) (3–7). Coil embolization for gastrointestinal bleeding and traumatic vascular lesions, in particular, is an alternative to surgery (8). Superselective catheterization even into small vessels has become possible due to advances in microcatheter technologies (9–12). However, as the aimed vessel may sometimes be too thin and/or tortuous, superselective catheterization can still be difficult to perform safely. The triaxial system was recently shown to contribute largely to superselective TACE for HCC (1,2). It has become easier to advance the 1.9-Fr non-tapered microcatheter to the aimed vessel using this system because the 2.7-Fr microcatheter prevented sagging or jumping by maintaining its position. These findings indicate that the 2.7-Fr microcatheter provides good support for the 1.9-Fr non-tapered microcatheter to advance even into thin tortuous vessels. Furthermore, the tip of the microcatheter is flexible and sometimes cannot be stabilized when coil embolization is performed with a conventional microcatheter; thus, there is a risk of coil misplacement (13). However, the 2.7-Fr microcatheter can keep its position and the 1.9-Fr non-tapered microcatheter can be stabilized with the triaxial system, such that coil embolization can be performed safely. Thus, if the triaxial system can be applied not only to TACE for HCC but also to coil embolization, it could potentially be very useful.

We attempted triaxial coil embolization using 0.010-inch GDCs while monitoring the voltage for detachment. Other small coils could be inserted into the 1.9-Fr non-tapered microcatheter, such as Cerecyte coils (Micrus Endovascular, San Jose, CA, USA) or Trufill Detachable Coil System Orbit coils (Codman Neurovascular, Raynham, MA, USA). If we attempt to use these coils, we believe that they should be detached inside of the microcatheter and then pushed to the outside of the microcatheter. However, when it is difficult to find the tip of the microcatheter because of existing coils, it is impossible to accurately confirm when the coil has dropped out of the microcatheter, which may be dangerous. Because of this, we consider GDCs to be the most appropriate coils for this system.

In this study, we acquired high technical and clinical success rates without complications. We believe that the voltage-dependent coil-detaching technique makes it possible to detach GDCs surely and safely in the triaxial system. However, we failed to deliver GDCs in a few procedures. One reason may have been that insufficient dripping of saline to the inside of the microcatheter caused a thrombus, resulting in the stacking of the GDCs. Therefore, it is very important to pay attention to the dripping of saline during this technique. Another reason may have been the incorrect connection of GDC cables. Therefore, the correct connection of GDC cables must be confirmed before the detaching procedure. Since all detachable coils have been recommended for use with a two-tip marker microcatheter, a trial of this technique should be performed with the personal responsibility of each interventional radiologist.

In conclusion, triaxial coil embolization may be performed safely and effectively using GDCs with the voltage-dependent coil-detaching technique.