EC-IC Bypass Using ELANA Technique

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14 EC-IC Bypass Using ELANA Technique

Introduction

High-flow EC-IC bypass using transplanted conduits in the form of radial artery and saphenous vein is a high-risk procedure performed infrequently. It is reserved for the treatment of aneurysms emanating from or in tumors in close proximity to large proximal intracranial vessels where vessel sacrifice and cranial blood flow replacement remains the safest treatment option for otherwise highly dangerous pathologies. The operations themselves, however, are also highly morbid in nature due to the risks associated with creating a novel conduit for blood flow from an extracerebral source to an intracerebral target with a transplanted vessel. The risks can be broken down into three categories: graft and attachment, occlusion time and associated maneuvers to protect the brain from ischemia and thrombus, and treatment of the aneurysm or tumor itself. The excimer laser–assisted nonocclusive anastomosis (ELANA) is a device combined with a technique designed to limit the risks associated with the second of these risk categories, or those associated with temporary vessel occlusion.

ELANA represents the results of the ideas and investigation of C. A. F. Tulleken and his group at the University Medical Centre in Utrecht, Holland, and spans a period from 1993 to the present. Their efforts arose partly in response to the EC-IC Bypass Study in the mid-1980s, which had disappointing results regarding the viability of STA-MCA bypasses in treating ischemic patients. Tulleken believed that the results of the study may have been different had the bypasses been more proximal in the circle of Willis with its resultant higher flows. However, making such high-flow bypasses would be problematic in the ischemic patient who was less likely to tolerate the temporary occlusion of the large proximal cerebral arteries while constructing the bypasses. In general, the incidence of perioperative stroke in creating high-flow bypasses is approximately 9.5%.13 Therefore, a nonocclusive method of augmenting flow would be of particular benefit to these patients.

The Utrecht group began to investigate the use of laser technology to develop a nonocclusive method of creating intracranial anastomoses. In the early 1990s, they developed a laser catheter and suction system designed to create a consistent attachment to the artery wall and a more consistent arteriotomy. The addition of a separate small platinum ring that allows the laser catheter to better interface with the recipient wall has led to an efficient system of creating nonocclusive cerebral bypasses. The stages of the development of ELANA have been reviewed in the literature4 with the first human cases performed in 1993. Minor modifications were made between 1993 and 1995 with the current technique and technology remaining quite stable over the past 15 years with minimal substantive change. This technique has similarly been reviewed previously in the literature.4 The ELANA system is currently being utilized in primarily three centers in Europe, one in Canada, and four in the United States. This chapter aims to review the ELANA system and technique, examine the data from clinical studies in human cases, and discuss its benefits along with its disadvantages over conventional high-flow bypass techniques while updating current thinking on its future with an eye toward future modifications that may make the technique even more desirable.

Technique

The ELANA technique is in actuality a simple modification of the steps involved in conventional conduit transplant bypass. The key difference lies in the intracranial arteriotomy step and the method of suturing the distal anastomosis. In conventional technique, temporary occlusion is performed to create an arteriotomy in the recipient vessel, which is then followed by microsurgically suturing the donor and recipient to one another prior to recirculation. The ELANA technique circumvents the temporary occlusion step by having the operator attach the vessels to one another before the arteriotomy step, thus allowing the arteriotomy to be performed after the anastomosis has already been created. In order to create this arteriotomy, a specialized ELANA catheter and a ring device have been developed to not only create the hole but to remove the flap of vessel wall as well. ELANA is not truly an anastomotic device but rather a laser-assisted hole-making system.

Two unique steps are necessary to create an ELANA anastomosis. First, a platinum ring of 2.6 to 2.8 mm in diameter is attached to the distal part of the donor vessel at a side table by flipping the distal end of the donor around the ring and microsurgically suturing using 4-8 😯 nylon sutures to secure it in place. Second, following microsurgically attaching the donor/ring construct to the recipient using 8-10 😯 prolene sutures and after the proximal anastomosis has been created, the ELANA catheter is used to create the arteriotomy using an excimer laser energy source with removal of the arterial “flap” using vacuum suction within the catheter (Figures 14–1 and 14–2). The laser catheter is composed of an outer array of laser fibers representing the “cutting” element surrounding an inner core of central suction (see Figure 14–2). The ELANA catheter is passed through the open end of the donor vessel or through a side slit of the donor to the recipient outer wall (Figure 14–3) and after 2 minutes of suction activation, the laser is activated for two to three 10-second bursts to create the arteriotomy. After the arteriotomy has been made, the catheter is withdrawn with the arterial flap attached to the central suction core (Figure 14–4).

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Figure 14–2 A, Computer-generated drawing of the donor/ring complex following anastomosis to recipient artery. B to D, Intraoperative photographs showing the ring/graft complex being sewn to the ICA wall with eight interrupted microsutures.

(From Langer DJ, Van Der Zwan A, Vajkoczy P, et al., Excimer laser-assisted nonocclusive anastomosis. An emerging technology for use in the creation of intracranial-intracranial and extracranial-intracranial cerebral bypass, Neurosurg Focus 2008;24(2):E6.)

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Figure 14–3 Photograph showing the ELANA catheter tip. Note inner suction surrounded by outer laser array.

(From Langer DJ, Van Der Zwan A, Vajkoczy P, et al., Excimer laser-assisted nonocclusive anastomosis. An emerging technology for use in the creation of intracranial-intracranial and extracranial-intracranial cerebral bypass, Neurosurg Focus 2008;24(2):E6.)

Once the laser step has been completed, a temporary clip is placed just proximal to the anastomosis on the donor side. This prevents back bleeding through the proximal open end of the donor graft or through the side slit (Figure 14–5). Bypasses can be created in a single-piece or two-piece fashion. A one-piece graft is the same as conventional except for the creation of a temporary side slit in the donor to allow catheter access to the anastomosis. A two-piece graft can also be performed with the distal portion of the donor sewn to the proximal portion, which is attached to an extracranial carotid source (Figures 14–6 and 14–7). ELANA can also be used to create novel IC-IC bypasses where the proximal donor source is an intracranial vessel such as A1, M1, or the internal carotid, and the distal target is to nearly any target vessel of sufficient caliber. The proximal arteriotomy is made using ELANA, while the distal arteriotomy is created using ELANA or conventional technique.

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Figure 14–5 A, Computer-generated drawing of the retrieved arteriotomy flap at the tip of the laser catheter. Intraoperative photographs showing the arterial wall flap, which is seen attached to the catheter tip (B) and removed (C).

(From Langer DJ, Van Der Zwan A, Vajkoczy P, et al., Excimer laser-assisted nonocclusive anastomosis. An emerging technology for use in the creation of intracranial-intracranial and extracranial-intracranial cerebral bypass, Neurosurg Focus 2008;24(2):E6.)

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Figure 14–7 Intraoperative photograph taken after the side slit of the vein graft has been closed with a continuous suture, the temporary clips are removed, and the bypass is opened. The proximal anastomosis in the ECA has been completed before the lasering step is performed.

(From Langer DJ, Van Der Zwan A, Vajkoczy P, et al. Excimer laser-assisted nonocclusive anastomosis. An emerging technology for use in the creation of intracranial-intracranial and extracranial-intracranial cerebral bypass, Neurosurg Focus 2008;24(2):E6.)

The ELANA technique thus allows creation of an EC-IC or novel IC-IC bypass throughout the cerebral vasculature in a nonocclusive fashion. The nonocclusive nature of ELANA allows conventional types of bypasses to be performed without flow arrest, arguably improving safety while also offering options in cases too high risk to bypass using conventional occlusive techniques due to concerns regarding temporary occlusion time.

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