Excimer Laser-assisted Nonocclusive Anastomosis Technique Research Articles

Technical Development of the Sutureless ELANA Clip Anastomosis Device

Abstract A cranial bypass can be a last resort procedure for patients suffering from complex neurovascular pathology. Since the clinically proven excimer laser-assisted nonocclusive anastomosis (ELANA) technique has become available, it is no longer necessary to temporarily close the recipient artery to facilitate an anastomosis. Aiming to simplify and shorten the operation time of the ELANA technique, a sutureless ELANA, the so-called SELANA slide (SEsl) was developed, but it failed during clinical study. We developed an improved device, the SELANA clip (SEcl).We describe the SEcl design and the first in vitro test results. The SEsl design was optimized with a clip at the backside, creating the SEcl which facilitates smooth and friction-free insertion in the recipient artery. Subsequently, the laser catheter was optimized by adding a grid and conus to provide an improved vacuum and flat reaction surface during lasing. We aimed to compare the SEcl to the current ELANA regarding application time difference, anastomosis success (“flap retrieval”) and technical difficulties. Hereto 32 ELANA and 32 SEcl anastomoses were performed on pressurized rabbit arteries in the ELANA practice system. Mean application time difference was 14.0 min (95%CI 13.0–15.0). The flap retrieval rate of the ELANA anastomoses was 94% (30/32) and 100% (32/32) for the SEcl technique. During the experiments no technical difficulties were encountered. The SEcl is technical feasible with promising simplicity and application times. However, extensive in vivo short-term and long-term experiments are indispensable before clinical application.

Vessel wall perforation mechanism of the excimer laser-assisted non-occlusive anastomosis technique.

The excimer laser assisted non-occlusive anastomosis (ELANA) technique is used to make anastomoses on intracerebral arteries. This end-to-side anastomosis is created without temporary occlusion of the recipient artery using a 308-nm excimer laser with a ring-shaped multi-fiber catheter to punch an opening in the arterial wall. Over 500 patients have received an ELANA bypass. However, the vessel wall perforation mechanism of the laser catheter is not known exactly and not 100 % successful. In this study, we aimed to understand the mechanism of ELANA vessel perforation using specialized imaging techniques to ultimately improve its effectiveness. High-speed imaging, high-contrast imaging, and high-sensitivity thermal imaging were used to study the laser wall perforation mechanism and reveal the mechanical and thermal effects involved. In vitro, rabbit arteries were exposed with the special designed laser catheter in a setup representative for the clinical setting, in which blood was replaced with a transparent UV absorbing liquid for visualization. We observed that laser vessel wall perforation was caused by explosive vapor bubbles tearing through the vessel wall, mostly within the first 20 of the total 200 pulses. Thermal effects were minimal. Unsymmetrical tension in the vessel wall inducing migration of the flap during laser exposure was observed in case of unsuccessful wall perforations. The laser wall perforation mechanism in the ELANA technique is primarily mechanical. Symmetric tension in the recipient vessel wall is essential and should be trained by neurosurgeons.

Evaluation of a Novel Laser-assisted Coronary Anastomotic Connector - the Trinity Clip - in a Porcine Off-pump Bypass Model

To simplify and facilitate beating heart (i.e., off-pump), minimally invasive coronary artery bypass surgery, a new coronary anastomotic connector, the Trinity Clip, is developed based on the excimer laser-assisted nonocclusive anastomosis technique. The Trinity Clip connector enables simplified, sutureless, and nonocclusive connection of the graft to the coronary artery, and an excimer laser catheter laser-punches the opening of the anastomosis. Consequently, owing to the complete nonocclusive anastomosis construction, coronary conditioning (i.e., occluding or shunting) is not necessary, in contrast to the conventional anastomotic technique, hence simplifying the off-pump bypass procedure. Prior to clinical application in coronary artery bypass grafting, the safety and quality of this novel connector will be evaluated in a long-term experimental porcine off-pump coronary artery bypass (OPCAB) study. In this paper, we describe how to evaluate the coronary anastomosis in the porcine OPCAB model using various techniques to assess its quality. Representative results are summarized and visually demonstrated.

Magnetic Resonance Imaging Flow Quantification of Non-Occlusive Excimer Laser-Assisted EC-IC High-Flow Bypass in the Treatment of Complex Intracranial Aneurysms

The patency of a bypass plays an important role in the postoperative recovery of patients especially when dealing with complicated intracranial aneurysms. In this study two-dimensional phase contrast magnetic resonance angiography (PC-MRA) was used to measure cerebral blood flow in 23 patients before extracranial-intracranial high-flow bypass surgery using the excimer laser-assisted non-occlusive anastomosis (ELANA) technique and in 15 patients following surgery. The results showed that PC-MRA is a suitable technique for assessing bypass patency and that with the ELANA technique the bypass has the capability of compensating the blood flow of an occluded internal carotid artery (ACI) in cases of complex aneurysms.

Patency, flow, and endothelialization of the sutureless Excimer Laser Assisted Non-occlusive Anastomosis (ELANA) technique in a pig model

The purpose of this study was to assess flow, patency, and endothelialization of bypasses created with the sutureless Excimer Laser Assisted Non-occlusive Anastomosis (SELANA) technique in a pig model. In 38 pigs, a bypass was made on the left common carotid artery (CCA), using the right CCA as a graft, with 2 SELANAs. Bypass flow was measured using single-vessel flowmetry. The pigs were randomly assigned to 1 of 12 survival groups (1, 2, 3, 4, 5, 6, 7, and 10 days; 2 and 3 weeks; and 3 and 6 months). One extra animal underwent the procedure and then was killed after 1 hour of bypass patency to serve as a control. Angiography was performed just before the animals were killed, to assess bypass patency. Scanning electron microscopy and histological studies were used to evaluate the anastomoses after planned death. The mean SELANA bypass flow was not significantly different from the mean flow in the earlier ELANA (Excimer Laser Assisted Non-occlusive Anastomosis) pig study at opening and follow-up. Overall SELANA bypass patency (87%) was not significantly different from the ELANA patency of 86% in the earlier study. Complete SELANA endothelialization was observed after 2-3 weeks, compared with 2 weeks in the earlier ELANA study. The SELANA technique is not inferior to the current ELANA technique regarding flow, patency, and endothelialization. A pilot study in patients is a logical next step.

The acute effect of increased laser energy during the excimer laser‐assisted non‐occlusive anastomosis procedure on the vessel wall of the recipient artery: A histopathological study

The excimer laser-assisted non-occlusive anastomosis (ELANA) technique is a way of making an anastomosis of vessels without temporal occlusion that is used for cerebral revascularization. Currently, 10 mJ of laser energy is used during the ELANA procedure. We have recently demonstrated that increasing the laser energy may increase flap retrieval rate. The aim of the present study was to study the acute effect of increased laser energy during the ELANA procedure on the recipient vessel wall. The ELANA technique was performed on the abdominal aortas of rabbits under anesthesia using three categories of laser energy (two laser episodes of 10, 13, and 15 mJ, respectively). The rabbits were subsequently sacrificed and the anastomoses were removed. A non-lased rabbit aorta was used as control. Recipient arteries were studied using histopathology and transmission electron microscopy. In all three categories of laser energy and in the control group, the tunica media and adventitia adjacent to the anastomosis were intact, apart from damage caused by sutures. In the control group, the endothelium was fully intact. In the 10 and 13 mJ subgroups, the endothelium was mostly intact [92% (range 85-98) and 87% (range 80-90) for 10 and 13 mJ, respectively]. In the 15 mJ subgroup, most of the endothelium was absent [32% (range 20-40) of endothelium intact], predominantly at the side opposed to the anastomosis. Increasing the laser energy during the ELANA procedure from 10 to 13 mJ does not cause additional acute damage to the vessel wall. Increasing the laser energy from 13 to 15 mJ results in increased acute damage of the endothelium, whereas tunica media and adventitia remain unaffected. Further studies are required to assess the long-term effects of increased laser energy during the ELANA technique.

Glue-Enhanced Excimer Laser-Assisted Nonocclusive Anastomosis: A Laboratory Investigation

Background/Aims: The excimer laser-assisted nonocclusive anastomosis (ELANA) technique has been developed as a clinical effective technique to perform intracranial high-flow bypass without temporary occlusion of cerebral vessels in otherwise untreatable or high-risk cerebrovascular diseases. We experimentally tested the application of a nonabsorbable cyanoacrylate-based sealant with the ELANA technique. Methods: Three technical in vitro variations of the ELANA anastomosis technique using Omnex^© glue and expanded polytetrafluoroethylene tube were compared with conventional sutured ELANA bypasses, resulting in 36 bypasses and 72 anastomoses. After that, the best resulting type was tested in 10 rabbits. Results: The ELANA bypass using Omnex and the expanded polytetrafluoroethylene tube technique offers better results in vitro in the retrieval of the arterial wall flap after arteriotomy, is faster, and the tensile strength of the bypasses performed with Omnex is comparable with those performed with conventional sutures. However, in 2 cases, we observed thrombosis of the vessel and considerable stiffness. Conclusions: The combining of the ELANA technique with 2-octyl cyanoacrylate and butyl lactoyl cyanoacrylate experimentally provides some advantages over the conventional ELANA technique. Further experimental studies should be performed in order to improve the safety and applicability of this technique.

Experimental Simplification of the Excimer Laser–Assisted Nonocclusive Anastomosis (ELANA) Technique

The excimer laser-assisted nonocclusive anastomosis (ELANA) technique facilitates the construction of an end-to-side anastomosis between a donor vessel and a recipient artery without the need to temporarily occlude the recipient artery. To test whether the surgically difficult ELANA technique can be simplified. In 42 rabbits, with the aorta as the recipient artery and human saphenous veins as donor grafts, we made 30 conventional ELANAs with 8 microsutures, 90 ELANAs with 4 microsutures (ELANA-4s), 40 ELANAs with 2 microsutures (ELANA-2s), and 90 sutureless ELANAs (SELANAs). SELANA involved a new ring design with 2 pins. ELANA-4, ELANA-2, and SELANA were each combined with 3 different sealants (Bioglue, Tachoseal, and Tisseel) and compared regarding application time, complications, and burst pressure. The conventional ELANA was constructed in a mean of 14.8 +/- 2.6 minutes. All experimental anastomoses were constructed significantly faster; the ELANA-4 in a mean of 10.9 +/- 1.3 minutes, the ELANA-2 in a mean of 5.4 +/- 1.7 minutes, and the SELANA in a mean of 2.5 +/- 1.8 minutes. All ELANA and ELANA-4 anastomoses were sufficiently strong with a burst pressure > 200 mm Hg, except for 1 insufficiently sealed ELANA-4 anastomosis. ELANA-2 was sufficiently strong only with Bioglue, showing a burst pressure > 280 mm Hg. SELANA was sufficiently strong with Bioglue or TachoSil, showing a burst pressure > 260 mm Hg. The ELANA technique can be simplified by reducing or even abandoning microsutures. Of the experimental anastomoses tested, we consider the SELANA technique combined with TachoSil of most potential benefit. Long-term survival studies will be performed in animals before we consider using any of these new techniques in patients.

Revival of extra-intracranial bypass surgery

Extra-intracranial bypass surgery has regained significant relevance over the past years. The aim of this review is to highlight the current indications and recent developments in this field. One main indication today is stroke prevention by flow augmentation in the setting of chronic cerebral hemodynamic ischemia which is defined as a combination of steno-oclusive cerebrovascular disease, inadequate collateralization, and loss of cerebrovascular reserve capacity. Another indication is flow replacement in the context of therapy of complex aneurysms and skull base tumors. The herein proposed revival of bypass surgery is due to the progress in individualized, tailored therapeutic strategies as well as patient selection. Furthermore, we witness a dramatic improvement in the surgical technique as well as the development of a broad armamentarium of different bypass types, which today allow tailored revascularization strategies for our patients. Finally, the revival of bypass surgery is also explained by significant technical progress. One of the major developments within the last years is the Excimer laser-assisted nonocclusive anastomosis technique which allows performance of an anastomosis without the need for temporary clipping, thus dramatically reducing the risk for perioperative ischemia in bypass surgery. Extra-intracranial bypass surgery has become a central part of a highly specialized, interdisciplinary strategy for the therapy of complex aneurysms and skull base tumors.

TREATMENT OF GIANT MIDDLE CEREBRAL ARTERY ANEURYSMS WITH A FLOW REPLACEMENT BYPASS USING THE EXCIMER LASER-ASSISTED NONOCCLUSIVE ANASTOMOSIS TECHNIQUE

To define the clinical value of the flow replacement bypass using the excimer laser-assisted nonocclusive anastomosis (ELANA) technique in the treatment of patients with a noncoilable, nonclippable giant intracranial aneurysm of the middle cerebral artery (MCA). Between 1999 and 2006, 22 patients with a giant intracranial aneurysm of the MCA were treated in our hospital with an ELANA flow replacement bypass and MCA occlusion. We collected data on patient characteristics, operative aspects, complications, and functional health scores using the modified Rankin Scale. Mean follow-up was 3.6 years (range, 0.2-7.7 yr). We were able to construct a patent bypass in 20 (91%) of 22 patients. All 34 ELANA attempts resulted in a patent anastomosis with a strong backflow directly after ELANA catheter retraction. The patients did not need to undergo temporary occlusion in any of the ELANA constructions. Mean +/- standard deviation intracranial-to-intracranial bypass flow was 53 +/- 13 ml/min. MCA aneurysm treatment was attempted in all 20 patients who had a patent bypass and was successful in 19 of them. There was a fatal hemorrhagic complication in one patient (5%), a nonfatal hemorrhagic complication in three patients (14%), and a nonfatal ischemic complication in six patients (27%). At follow-up, 17 patients (77%) had a functionally favorable outcome (modified Rankin Scale score at follow-up was the same as or less than the preoperative modified Rankin Scale score). All of these patients were independent at follow-up (modified Rankin Scale score < or =2). This study demonstrates satisfactory results in the treatment of giant MCA aneurysms with an ELANA flow replacement bypass, considering the very grave natural history and treatment complexity of these lesions. The ELANA technique is a useful tool in the treatment armamentarium of the vascular neurosurgeon.

TREATMENT OF GIANT AND LARGE INTERNAL CAROTID ARTERY ANEURYSMS WITH A HIGH-FLOW REPLACEMENT BYPASS USING THE EXCIMER LASER-ASSISTED NONOCCLUSIVE ANASTOMOSIS TECHNIQUE

To define the clinical value of the high-flow replacement bypass using the excimer laser-assisted nonocclusive anastomosis technique in the treatment of patients with a noncoilable, nonclippable giant or large intracranial aneurysm of the internal carotid artery (ICA). We studied 34 patients with a giant intracranial aneurysm of the ICA proximal to its bifurcation who were treated with an extracranial-intercranial high-flow replacement bypass in our hospital between 1999 and 2004. We retrospectively collected data for patient characteristics, operative aspects, complications, and functional health scores using the modified Rankin scale. Long-term data were updated by questionnaire and telephone survey. Mean long-term follow-up period was 3.3 years (range, 0.6-5.6 yr). We were able to construct a patent bypass in 33 out of 34 patients (97%). In six patients (17%), we needed two bypass attempts. In one patient (3%), the bypass was technically impossible. After bypass construction, we occluded the ICA during or after surgery in 32 patients (94%), causing aneurysm thrombosis in all of these patients. A fatal complication occurred in two patients (6%) before we could occlude the ICA. A nonfatal complication occurred in seven patients (21%). In the long term, 25 patients (74%) had a favorable outcome and 27 patients (79%) were independent (modified Rankin scale, <3). This study shows that the excimer laser-assisted nonocclusive anastomosis high-flow replacement bypass, which provides maximum brain protection because of its nonocclusive character, is a reliable and effective method to treat these otherwise untreatable patients.

Excimer laser–assisted nonocclusive anastomosis

Excimer laser-assisted nonocclusive anastomosis (ELANA) has been developed over the past 14 years for assistance in the creation of intracranial bypasses. The ELANA technique allows the creation of intracranial-intracranial and extracranial-intracranial bypasses without the need for temporary occlusion of the recipient artery, avoiding the inherent risk associated with occlusion time. In this review the authors discuss the technique and its indications, while reviewing the clinical results of the procedure. The technique itself is explained using cartoon drawings and intraoperative photographs. Advantages and disadvantages of the technique are also discussed.

Excimer laser–assisted nonocclusive anastomosis

Excimer laser–assisted nonocclusive anastomosis (ELANA) has been developed over the past 14 years for assistance in the creation of intracranial bypasses. The ELANA technique allows the creation of intracranial–intracranial and extracranial–intracranial bypasses without the need for temporary occlusion of the recipient artery, avoiding the inherent risk associated with occlusion time. In this review the authors discuss the technique and its indications, while reviewing the clinical results of the procedure. The technique itself is explained using cartoon drawings and intraoperative photographs. Advantages and disadvantages of the technique are also discussed.

Sutureless nonocclusive bypass surgery in combination with an expanded polytetrafluoroethylene graft

Cerebral aneurysms that cannot be treated by clip or coil placement can be treated with high-flow bypass surgery using techniques such as the excimer laser-assisted nonocclusive anastomosis (ELANA). To simplify the technique, a sutureless ELANA (SELANA) was developed in combination with an expanded polytetrafluoroethylene (ePTFE) graft. In 18 rabbits a bypass was constructed on the abdominal aorta using the SELANA technique with an ePTFE graft, resulting in 18 bypasses and 36 anastomoses. Short-term effects were analyzed in the first 2 weeks and at 2 and 3 months after the procedure. Patency was evaluated using quantitative ultrasound flowmetry. The anastomotic sites were studied using scanning electron microscopy. Construction of the bypass using the SELANA technique was easier and faster (15-25 minutes) compared with bypasses made with the ELANA technique (> 90 minutes). At the end of follow-up, 16 of 18 bypasses were patent. Of 36 SELANA anastomoses, 32 could be completed without short temporary occlusion of the recipient vessel. Scanning electron microscopy showed complete coverage of all anastomoses with neointimal repair tissue after 10 days. The SELANA technique provides further advantages over the conventional ELANA technique in ease of use and shortening of procedure time. The patency rate in this series was 89% and neointima repair tissue at the anastomosis site was complete after 10 days. Further experimental studies of the long-term patency and safety of this technique are necessary before clinical application.

The Use of the Excimer Laser-assisted Anastomosis Technique Alleviates Neuroanesthesia During Cerebral High-flow Revascularization

In patients with complex intracranial aneurysms or skull base tumors, parent vessel occlusion and flow replacement by high-flow bypass surgery is a demanding therapy, both for the neurosurgeon and the neuroanesthesiologist. One reason for this is the need for prolonged temporary occlusion of a major cerebral artery, which carries a high risk of perioperative ischemia and necessitates versatile neuroprotective measures during anesthesia. Recently, a novel excimer laser-assisted nonocclusive anastomosis (ELANA) technique has been introduced, circumventing the need for temporary occlusion of cerebral vessels. We hypothesized that the use of this ELANA technique would facilitate also the neuroanesthesiologic management of these patients. To test this, we reviewed the details of the neuroanesthesiologic management of patients undergoing ELANA high-flow bypass surgery at our institution. Twenty-nine patients with giant aneurysms (n=27) or skull base tumor (n=2) who were undergoing parent vessel occlusion and permanent flow replacement by high-flow bypass surgery using the ELANA technique were investigated retrospectively. The records of the patients were analyzed for induction and maintenance of anesthesia, fluid therapy, transfusion requirements, hemodynamic parameters, and brain protective strategies. Although we are not able to provide a sufficient body of cohort data to compare the neuroanesthesiologic management of patients undergoing the conventional anastomosis technique with management using the ELANA technique, in each of our reported cases the conventional anastomosis technique would have entailed a high probability of prolonged temporary occlusion that would, in turn, have warranted intensive brain-protective strategies. The observation that use of the ELANA technique precluded the necessity of brain-protective strategies without entailing perioperative cerebral infarction suggests that the ELANA technique supports the neurosurgeon in creating difficult permanent intracranial anastomoses and also facilitates neuroanesthesiologic management of patients undergoing cerebral high-flow revascularization procedures.

Expanded polytetrafluoroethylene graft for bypass surgery using the excimer laser–assisted nonocclusive anastomosis technique

Patients with complex craniocerebral pathophysiologies such as giant cerebral aneurysms, skull base tumors, and/or carotid artery occlusive disease are candidates for a revascularization procedure to augment or preserve cerebral blood flow. However, the brain is susceptible to ischemia, and therefore the excimer laser-assisted nonocclusive anastomosis (ELANA) technique has been developed to overcome temporary occlusion. Harvesting autologous vessels of reasonable quality, which is necessary for this technique, may at times be problematic or impossible due to the underlying systemic vascular disease. The use of artificial vessels is therefore an alternative graft for revascularization. Note, however, that it is unknown to what degree these grafts are subject to occlusion using the ELANA anastomosis technique. Therefore, the authors studied the ELANA technique in combination with an expanded polytetrafluoroethylene (ePTFE) graft. The experimental surgeries involved bypassing the abdominal aorta in the rabbit. Ten rabbits were subjected to operations representing 20 ePTFE graft-ELANA end-to-side anastomoses. Intraoperative blood flow, followup angiograms, and long-term histological characteristics were assessed 75, 125, and 180 days postoperatively. Angiography results proved long-term patency of ePTFE grafts in all animals at all time points studied. Data from the histological analysis showed minimal intimal reaction at the anastomosis site up to 180 days postoperatively. Endothelialization of the ePTFE graft was progressive over time. The ELANA technique in combination with the ePTFE graft seems to have favorable attributes for end-to-side anastomoses and may be suitable for bypass procedures.

Treatment of Giant and Large Internal Carotid Artery Aneurysms With a High-Flow Replacement Bypass Using the Excimer Laser-Assisted Nonocclusive Anastomosis Technique

To define the clinical value of the high-flow replacement bypass using the excimer laser-assisted nonocclusive anastomosis technique in the treatment of patients with a noncoilable, nonclippable giant or large intracranial aneurysm of the internal carotid artery (ICA). We studied 34 patients with a giant intracranial aneurysm of the ICA proximal to its bifurcation who were treated with an extracranial-intercranial high-flow replacement bypass in our hospital between 1999 and 2004. We retrospectively collected data for patient characteristics, operative aspects, complications, and functional health scores using the modified Rankin scale. Long-term data were updated by questionnaire and telephone survey. Mean long-term follow-up period was 3.3 years (range, 0.6-5.6 yr). We were able to construct a patent bypass in 33 out of 34 patients (97%). In six patients (17%), we needed two bypass attempts. In one patient (3%), the bypass was technically impossible. After bypass construction, we occluded the ICA during or after surgery in 32 patients (94%), causing aneurysm thrombosis in all of these patients. A fatal complication occurred in two patients (6%) before we could occlude the ICA. A nonfatal complication occurred in seven patients (21%). In the long term, 25 patients (74%) had a favorable outcome and 27 patients (79%) were independent (modified Rankin scale, <3). This study shows that the excimer laser-assisted nonocclusive anastomosis high-flow replacement bypass, which provides maximum brain protection because of its nonocclusive character, is a reliable and effective method to treat these otherwise untreatable patients.

The Excimer Laser-Assisted Nonocclusive Anastomosis Practice Model: Development and Application of a tool for Practicing Microvascular Anastomosis Techniques

To practice microsurgical skills, several experimental models are available that diminish the need for experimental animals. We defined criteria with which such models should comply, and we tested whether the models described in literature, as well as our own practice model, comply with these criteria. We defined the criteria to which these models should comply, and we performed a literature search on microvascular practice models. During the development of the Excimer laser-assisted nonocclusive anastomosis technique, we designed our own Excimer laser-assisted nonocclusive anastomosis Practice Model (EPM) according to those criteria, and we compared that model with the models described in the literature. All practice models could be categorized into three groups: beginner, moderate, and advanced. Our EPM complies with almost all criteria defined in the beginner and moderate groups and has much in common with the models that are categorized in the advanced group. In consideration of the methods to learn microvascular surgical techniques, the EPM can be used for a very long time before the need for living animals arises. This last aspect remains an inescapable condition for practicing microsurgical skills. However, with use of the EPM or another practice model, the amount of experimental animals can be drastically reduced.

Long-term reendothelialization of excimer laser—assisted nonocclusive anastomoses compared with conventionally sutured anastomoses in pigs

In contrast to conventional anastomosis methods, the excimer laser-assisted nonocclusive anastomosis (ELANA) technique involves a platinum ring and intima-adventitia apposition with a rim of medial and adventitial layers exposed to the bloodstream. The authors assessed the reendothelialization of porcine carotid arteries through ELANA compared with conventional anastomosis by using scanning electron microscopy. In 28 pigs a bypass with one ELANA and one conventional anastomosis was made on the left common carotid artery. All patent anastomoses were evaluated intraoperatively with the aid of an ultrasonographic flowmeter and postoperatively by using scanning electron microscopy at 2 weeks, 2 months, 3 months, and 6 months thereafter. Twenty-four of 28 bypasses (48 of 56 end-to-side anastomoses) were fully patent at the time of evaluation. On scanning electron microscopic evaluation of the bypasses, all 48 patent anastomoses showed complete reendothelialization, including all 24 ELANAs in which the endothelium covered the rim and the laser-ablated edge completely. No endothelial difference was observed between conventional anastomoses and ELANAs, aside from the obvious anatomical differences like the platinum ring, which had been completely covered with endothelium. At 6 months postsurgery, remodeling of the ELANA was observed, leaving the ring covered with a layer of endothelium as the most narrow part of the anastomosis. In long-term experiments, ELANA allows reendothelialization comparable to that achieved with conventional anastomosis. Considering its nonocclusive and high-flow characteristics, the ELANA technique is preferable in cerebral revascularization procedures.

Flow quantification of the non-occlusive excimer laser-assisted EC-IC bypass.

For six years, we used the Excimer laser-assisted nonocclusive anastomosis technique for high-flow revascularization of the brain in patients with either nonclippable and noncoilable giant aneurysms of the internal carotid or basilar artery or progressive stroke associated with occlusive disease of the internal carotid artery. The aim of this study is to assess the blood flow capacity of this type of Extra-Intracranial bypass and its haemodynamic behaviour over time. Twenty-six patients with a giant aneurysms and 8 patients with occlusive disease of the internal carotid artery were treated with the nonocclusive Excimer laser assisted EC-IC bypass. intra-operatively, direct measurements of flow in the EC-IC bypass were performed in all patients (Transonic Systems, Inc., Ithaca. NY). Postoperatively, follow up measurements of flow were performed with MR angiography in 14 patients with a giant aneurysm after occluding the internal carotid artery, and 7 patients with occlusive carotid disease. The mean flow in the laser assisted bypasses in the group of patients with a giant aneurysm was 158 ml/min after ligation or balloon occlusion of the ICA. The mean flow of the laser assisted bypass in the group of patients with ICA occlusive disease was 130 ml/min. A comparison with data on flow capacity of conventional EC IC bypasses is made. A demonstrated increase of flow in the bypass during follow up is discussed from a haemodynamic point of view. The results of this study demonstrate that the flow capacity of the nonoccluding excimer laser assisted bypass is much higher than the capacity of the conventional, more peripherally located conventional EC IC bypass, and should therefore be denoted as High-Flow EC IC bypass. Consequently, this type of bypass can be a powerful and safe tool in new revascularization strategies.