Application of the Willis covered stent for the management of posttraumatic carotid-cavernous fistulas: An initial clinical study
Aims: To evaluate the feasibility of using the Willis covered stent in the management of patients with traumatic carotid-cavernous fistulas (CCFs). Materials and Methods: Twelve consecutive patients with 14 post-traumatic CCFs referred for treatment with Willis covered stents were enrolled in this prospective study. Data on technical success, initial and final angiographic results, mortality, morbidity and final clinical outcome were collected. Follow- up was at one, three, six, and 12 months, and yearly thereafter. Results: Deployment of covered stents was technically successful in all the patients without complications. One covered stent was placed in eight patients and two covered stents in four. Angiographic results following stent placement showed a complete occlusion in nine patients with 11 CCFs, and an incomplete occlusion in three patients. Angiographic follow-up (mean, 14.00 ± 6.93 months; range, 6-24 months) revealed complete occlusion and no obvious in-stent stenosis in all the patients. Clinical follow-up (mean, 17.75 ± 7.05 months; range, 7-28 months) demonstrated full recovery in 11 patients, and improvement in one. Conclusion: This initial experience indicates that the use of the Willis covered stent is a feasible procedure and may be an alternative treatment option for CCFs.
Keywords: Carotid-cavernous fistulas, covered stents, endovascular treatment, trauma
Traumatic carotid-cavernous fistulae (CCFs) are rare and represent 0.2-0.3% of blunt or penetrating traumatic injuries of the carotid arteries. Surgical repair and detachable balloon (DBs) are the most commonly used treatment options. Direct surgical repair with distal internal carotid artery (ICA) preservation still presents a challenge due to relative inaccessibility.  Although embolization with DBs has been widely accepted as a first-line and classical therapeutic option with reported success rates of 75-88%. ,, Residual or recurrent CCFs, as well as pseudoaneurysm formation, frequently occur due to incomplete occlusion of the orifice, especially in patients with difficult or complex CCFs. Recently, successful use of covered stents in the management of posttraumatic CCFs, has been reported. ,,, This technique not only preserves and reconstructs the pathologic parent vessel to simplify the endovascular procedure, but also shortens the procedure time and reduces the cost by placing the stent across the ostium of the fistula. The purpose of this study was to present our preliminary experience of the evaluation and feasibility of using a Willis covered stent in the treatment of posttraumatic CCFs.
Between June 2009 and September 2011, 12 (eight males and four females; mean age 32.50 ± 10.72 years; range, 15-52 years) consecutive patients with posttraumatic CCFs referred for treatment with a Willis covered stent were enrolled into the study. The study was approved by the institutional review board and written informed consent was obtained from all patients or immediate relatives. The demographics, clinical characteristics, endovascular treatment and follow-up outcomes of the patients are summarized in [Table 1]. Diagnosis of CCF was primarily made from the patient's medical history and cerebral angiograms. A delay in diagnosis and endovascular treatment occurred in all the patients. Clinical symptoms at presentation included pulsating exophthalmos (n=12), retroorbital bruit (n=12), chemosis (n=9), decreased visual acuity (n=4), ophthalmoplegia (n=3), and blindness (n=1). Angiograms of six arteries performed in all patients revealed bilateral CCFs in two patients and unilateral in ten.
Willis covered stent placement
The Willis balloon-expandable covered stent (MicroPort Medical Company, Shanghai, China), has been previously described in detail. ,,, Briefly, the stent consists of three parts: A bare stent, an expandable polytetrafluoroethylene (ePTFE) membrane and a balloon catheter. Willis covered stents 3.5, 4.0, 4.5, and 5.0 mm in diameter and 7, 10, 13, 16, and 19 mm in length are available. The technique of placing the Willis covered stent and peri-procedure management have been previously described. ,,, Briefly, all procedures were performed under general anesthesia. After positioning a 6-F Envoy (Cordis, Miami Lakes, Fla) guiding catheter in the internal carotid artery (ICA), a microguidewire (Transend floppy, Boston Scientific) was navigated into a distal branch of the middle cerebral artery. With roadmap guidance, the Willis covered stent was navigated over the microguidewire, and then bridged the orifice of the fistula. Angiography was performed immediately after balloon deflation to confirm the correct placement of the stent and satisfactory occlusion of the fistula.
Prior to the procedure, patients received aspirin (100 mg/d) and clopidogrel (75 mg/d) for three consecutive days. Patients received a bolus dose of heparin 5000 IU at the start of the procedure, followed by a continuous infusion of 1000 IU/h, with the aim of maintaining the activated clotting time above 300 sec. Heparin was administered for 48 h after the procedure, and patients were instructed to take aspirin (100 mg/d) and clopidogrel (75 mg/d) orally for six months to avoid thrombosis and in-stent stenosis.
Follow-up and postoperative outcome evaluation
Patients were followed at one, three, six, and 12 months, and thereafter annually and assessment included a clinical and angiographic assessment. Data on technical success, initial and final angiographic results, mortality, morbidity and the final clinical outcome, were retrospectively collected and analyzed by both authors at the time of discharge and at the end of the follow-up period.
The angiographic data was categorized into complete occlusion, with no residual cavity and no endoleak, or incomplete occlusion, with a residual cavity or an endoleak. The clinical follow-up assessment was graded into: Full recovery from the neurologic symptoms, improved neurologic symptoms, unchanged symptoms, or deterioration in neurologic symptoms. ,,,
Primary procedural results
The deployment of the covered stents was technically successful in all the patients. Complete occlusion of the fistulae without endoleak was achieved in eight patients with ten CCFs [Figure 1], and transient endoleaks into the sinus cavernosus were observed in four patients with four CCFs immediately after the deployment of the initial Willis covered stent (Cases 2, 3, 8 and 11). The endoleak was dramatically reduced to a minimal endoleak (a very small endoleak) in two CCFs (Cases 8 and 11) and persisted in two CCFs after balloon reinflation (Cases 2 and 3). Additional covered stent placements at the proximal end of the initial stent were performed for two CCFs with persistent endoleak, which resulted in complete occlusion of one fistula (Case 3) and one minimal endoleak (Case 2). One covered stent was placed in eight patients and two covered stents in four, including two patients with two CCFs. The angiographies obtained at the end of the initial procedure showed that complete occlusion was achieved in nine patients with 11 CCFs (75.0%), and an incomplete occlusion in three (3/12, 25.0%).
There were no adverse events related to navigation of the covered stent in any of the patients. Neurologic examination after the procedure and before discharge exhibited no new neurologic symptoms and no recurrent pulsating exophthalmos or retroorbital bruit in any of the patients.
Follow-up angiographic and clinical results
Angiography follow-up (mean, 14.00 ± 6.93 months; range, 6-24 months) was completed in all patients. All 12 subjects underwent the three and six-month follow- up angiography, while nine underwent the 12-month follow-up angiography, and two patients the 24-month post-procedure angiography. No morbidity or mortality occurred in any of the patients in the follow-up study period.
On the three-month follow-up angiography, in nine patients with 11 CCFs and initial complete exclusion, complete occlusion of the fistula was still observed with reconstruction of the ICA. In three patients with three CCFs with an initial residual minimal endoleak, all three CCFs observed a spontaneous resolution of the endoleak with reconstruction of the ICA. No obvious in-stent stenoses were noted in any of the 12 patients. In the nine patients with a 12-month follow- up angiography, complete occlusion of the fistula and parent artery patency persisted without in-stent stenosis. Angiographies obtained at the final follow-up demonstrated complete occlusion in all 12 patients with 14 CCFs.
Clinical follow-up data was obtained from all the patients between 7 and 28 months post stent placement with a mean of 17.75 ± 7.05 months. Clinical evaluations performed at the final follow-up showed a full recovery in 11 patients, and unchanged clinical status in one patient who was blind. During the available follow- up period, no occurrence of pulsating exophthalmos, retroorbital bruit or chemosis was reported by any of the patients.
Posttraumatic CCF is an infrequent complication resulting from craniomaxillofacial injuries or basal skull fracture. The optimal treatment is exclusion of the fistula from the circulation while preserving ICA patency. Transarterial balloon occlusion of CCFs has been widely accepted and used in many centers the world over, as it is relatively easy and inexpensive, and in addition, it is associated with high rates of fistula occlusion and preservation of the ICA. ,,,, However, residual or recurrent CCF, as well as pseudoaneurysm formation, have often been major problems in balloon occlusion of the fistula, due to incomplete occlusion of the orifice with DBs. Although coil embolization is another relatively easy and widely used approach for the treatment of posttraumatic CCFs, ,,,,,, especially for recurrent or complex CCFs, it is expensive, and not always safe or effective for large or high-flow fistulas, and is associated with sacrifice of the ICA in certain instances. ,,
Of late, the covered stent has been successfully used for the treatment of aneurysms, pseudoaneurysms, dissections, and CCFs, with promising results achieved. ,,,,,,, Using a covered stent, closure of the CCF orifice is potentially quick and relatively straightforward, and without the occurrence of endoleaks. The drawbacks are residual or recurrence of the CCFs, as well pseudoaneurysm formation does not occur once the orifice of the CCF is completely occluded. In this study, placement of the Willis covered stent was technically successful in all the patients with no procedure-related complications, and complete occlusion of the fistula was achieved in all patients without the occurrence of recanalization and obvious stenosis on final angiograms. The significant improvement in complete occlusion rates observed during the angiographic follow-up period seemed to be predominantly attributable to occlusion of the orifice of the fistula. These results indicate that the use of the Willis covered stent was a feasible approach for the treatment of CCFs.
Recently, small series of ICA aneurysm or CCF successfully treated with Jostent have been reported. ,, The Jostent covered stent, which is dedicated for use in coronary artery disease, is a composite balloon-expandable stent with an ultrathin layer of ePTFE sandwiched between two stainless steel stents, and this device is manually compressed over a conventional angioplasty balloon. , Compared with the Jostent covered stent, the Willis covered stent is specifically designed for use in the intracranial vasculature and is also a composite balloon-expandable stent with an ultrathin layer of ePTFE (30-50 μm) glued outside the length of the stent.,,, The Willis covered stent is mounted on a deflated balloon catheter with an outside diameter of 3.8 Fr (1.27 mm). ,,, Therefore, the Willis covered stent is easier than that of the Jostent covered stent to negotiate tortuous vascular segments at the skull base due to its monolayer thin stent and delivery system. Compared with the established embolization technique with coils, a covered stent has the following advantages: 1) a relatively simple and rapid performance; 2) no coil herniation, delayed migration, and coil loop protrusion; 3) disappearance or reduction of mass effects in large CCFs; and 4) no residual or recurrent CCFs as well as pseudoaneurysm formation.
Our results have potentially important clinical implications. The use of a covered stent rather than detachable balloons or coils in patients with CCFs will substantially increase the complete occlusion and anatomic cure rates, and eliminate recanalization and mass effect. In addition, considerable savings can be achieved by avoiding the costs of repeated coiling, as well as the costs of treating recurrent CCFs. In this study, one patient with blindness prior to stent placement remained blind in the follow-up, this was due to delayed diagnosis and treatment. Although the covered stent has potentially important clinical implications, we must highlight the importance of an urgent ophthalmologic exam for early and accurately diagnosis of the CCFs and determine the urgency of treatment for these patients with CCFs to avoid the occurrence of delayed complications, such as decreases visual acuity or blindness.
The present study has some limitations. The number of patients treated is small. Thus, expanded clinical trials are required to determine the long-term outcomes. Secondly, in-stent stenosis might occur in patients who do not receive regular anticoagulation medication after stent placement. We emphasize that all patients must comply with standard anticoagulant and antiplatelet therapy (aspirin 100 mg/d and clopidogrel 75 mg/d orally) for six months after stent placement. In conclusion, our initial results indicate that the use of the Willis covered stent is a feasible procedure, and may serve as an alternative treatment for CCFs. Longer term follow-up and expanded clinical trials are needed.