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Abstract
Background Deconstructive approaches may be necessary to treat a variety of neurovascular pathologies. Recently, a new device has become available for endovascular arterial occlusion that may have unique applications in neurovascular disease. The Micro Vascular Plug (MVP, Reverse Medical, Irvine, California, USA) has been designed for vessel occlusion through targeted embolization.
Purpose To report the results from our initial experience with eight consecutive patients in whom the MVP was used to achieve endovascular occlusion of an artery in the head and neck.
Methods Eight consecutive patients treated over a nine-month period were included. The patients’ radiographic and electronic medical records were retrospectively reviewed. Specifically demographic information, clinical indication, site of arterial occlusion, size of MVP, time to vessel occlusion, clinical complications, use of other secondary embolic agents, and clinical outcome were recorded. Follow-up information when available is presented.
Results The MVP was used in eight patients for the treatment of neurovascular disease. Indications for treatment included post-traumatic head/neck bleeding (n=3), carotid–cavernous fistula (1), vertebral–vertebral fistula (1), giant fusiform vertebral aneurysm (1), stump-emboli after carotid dissection (1), and iatrogenic vertebral artery penetrating injury (1). One device was used in five patients, two in two patients, and one patient with extensive vertebral–vertebral venous fistula required three plugs to effectively trap the fistula from proximal and distal aspects. Vessel occlusion was obtained in <2 min in each case and there were no procedural complications. Four patients were followed up and no incidence of plug migration or vessel recanalization was seen.
Conclusions To the best of our knowledge, this is the first series reporting the use of MVP in neurovascular disease. Use of this device may be associated with shorter procedural times and cost savings in comparison with the use of microcoils for vessel occlusion. Our experience shows that MVP can have unique applications in neurovascular pathologies and it complements other occlusive devices.
- Artery
- Device
- Intervention
- Angiography
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Introduction
A deconstructive approach with parent vessel occlusion is necessary for the treatment of a number of neurovascular lesions. These lesions include pseudoaneurysms and giant aneurysms, iatrogenic and penetrating neurovascular injuries, and direct arteriovenous fistulas of the carotid and vertebral arteries, among others. Endovascular devices commonly used for such deconstructive approaches include detachable balloons, microcoils, liquid embolic agents or the AMPLATZER vascular plug (St Jude Medical, St Paul, Minnesota, USA).1–5
A new device for arterial occlusion has been introduced recently that may have unique applications in neurovascular disease. The Micro Vascular Plug (MVP) consists of an electrolytically detachable ovoid Nitinol exoskeleton and its proximal portion is partially covered with polytetrafluoroethylene (PTFE) to ensure prompt cessation of blood flow. The device is resheathable and can be deployed quickly and predictably through a 0.021 inch (for a 3 mm device) or 0.027 inch (for a 5 mm device) microcatheter. In this series, we report the results from our initial experience with eight consecutive patients in whom the MVP was used to achieve endovascular occlusion of an artery in the head and neck.
Methods
Approval for this study was obtained from the University of Maryland institutional review board. From July 2013 to February 2014, eight patients received endovascular vessel occlusion using the MVP. The patients’ radiographic and electronic medical records were reviewed retrospectively. The data were collected consecutively and no patient was excluded. Demographic information, clinical indication, site of arterial occlusion, size of MVP, time to vessel occlusion, clinical complications, use of secondary embolic agents, clinical outcome, and follow-up imaging were recorded.
Device description and vessel occlusion technique
The MVP is a self-expanding occlusive device (figure 1). It has a detachable ovoid-shaped embolic plug made from Nitinol. The proximal portion of the plug is partially covered with a PTFE lining. The device is available in two sizes: 3 mm (MVP-3) and 5 mm (MVP-5).
Unrestrained Micro Vascular Plug-5 device deployed on the procedural table.
Unconstrained, the MVP-3 expands to a maximum diameter of 5.3 mm, and the MVP-5 expands to 6.5 mm. For both the 3 and 5 mm devices, the unconstrained length is 12 mm. The device is soldered to a pusher wire and has an electrolytic detachment mechanism similar to Guglielmi detachable coils. The intended vessel size for an MVP-3 is 1.5–3.0 mm and for the MVP-5, 3.0–5.0 mm.6 To deploy the device it is positioned within the desired vessel and unsheathed through a microcatheter, while the delivery wire is held in a constant position. Once the proximal marker is freely within the vessel and the device is deemed stable, it can be electrolytically detached. The detachment time is typically <1 min.
Results
This series of eight patients is described in table 1. Patient ages ranged from 18 to 72. Primary indications included post-traumatic head/neck bleeding (n=3), carotid–cavernous fistula (CCF) (1), vertebral–vertebral fistula (1), giant fusiform vertebral aneurysm (1), stump-emboli after carotid dissection (1), and iatrogenic vertebral artery penetrating injury (1).
Demographics and intraprocedural results
All treatments were technically successful and there was no incidence of maldeployment or failed deployment. One device was used in four patients, two devices in three patients and one patient with extensive vertebral–vertebral venous fistula required three plugs to effectively trap the fistula from both ends. Angiography was performed 1–2 min after MVP plug deployment. Vessel occlusion was obtained in <2 min in each case and there were no procedural complications. Four of the eight patients have undergone follow-up DSA studies and no incidence of plug migration or parent vessel/target lesion recanalization has been seen.
Representative cases
Three representative cases are described in detail below.
Patient 4 is a teenager who had had a gunshot wound to the face. The patient presented after initial resuscitation with continuous hemorrhage from the bullet entry and exit sites. Left facial and lingual artery injuries were diagnosed during angiography. Within the proximal portion of the lingual artery, an MVP-3 was deployed, resulting in immediate cessation of blood flow. The facial artery stump did not demonstrate active extravasation and measured only 8 mm in length, so microcoils were used to occlude the artery. After the procedure, the surgical packing was removed and there was no recurrence of bleeding.
Patient 7 is a middle-aged person who presented with headache, proptosis, and diplopia. A high-flow CCF was diagnosed by MRI and angiography. The internal carotid artery (ICA) defect was deemed to be large and the patient passed a temporary balloon test occlusion. Two separate attempts were made to coil the high-flow CCF and ICA through transvenous and transarterial approaches. After the deployment of 88 coils and dense packing of the cavernous sinus and the cavernous ICA, rapid flow still persisted across the fistula. Two MVP-5 devices were deployed in the precavernous and petrous segments of the ICA. Blood flow through the ICA and the CCF was halted within 3 min of deploying the first device (figure 2). A 3-month follow-up DSA showed complete CCF and ICA occlusion.
(A and B) Case number 7: anteroposterior (A) and lateral (B) views of a high-flow carotid-cavernous fistula (CCF) seen through injection of the left internal carotid artery in a middle-aged patient. (C and D) Persistent flow was seen within the lesion after dense packing (C) of the left internal carotid artery and cavernous sinuses. The first Micro Vascular Plug (MVP) plug is being placed in the precavernous segment (arrow). (E) Stagnant flow seen within the left internal carotid artery (ICA) one minute after placement of two tandem 5 mm MVP devices. (F) Contralateral ICA injection reveals good cross-flow across the anterior communicating artery to the left hemisphere and complete occlusion of the CCF.
Patient 8, a person in the 4th decade of life, had had an iatrogenic right vertebral artery injury during a C5–6 anterior cervical discectomy and fusion. The surgical procedure resulted in brisk intraoperative hemorrhage controlled through surgical packing. A postoperative CT angiogram was consistent with a vertebral artery dissection and pseudoaneurysm. Diagnostic cerebral angiography confirmed a pseudoaneurysm of a congenitally hypoplastic right vertebral artery. The left vertebral artery was patent and in this patient the dominant supply was to the posterior circulation. The lesion was treated with a single MVP-3 device placed in the right vertebral artery. Less than a minute after device release, occlusion of the right vertebral artery occurred (figure 3).
(A) Case number 8: an anteroposterior catheter angiogram of the right subclavian artery demonstrating a V1 segment vertebral pseudoaneurysm (arrow) adjacent to the surgical hardware. (B) Intraprocedural roadmap during Micro Vascular Plug deployment. (C) One minute after deployment the right vertebral angiogram shows complete vessel occlusion.
Discussion
A number of products are available for endovascular occlusion of vessels. These include liquid embolic agents, microcoils, and plug devices such as the AMPLATZER vascular plug and the MVP. Each of these products has its own unique advantages and limitations. No single method of vessel occlusion is universally applicable and some of these agents are complementary.
Liquid embolic agents, including Onyx and N-butyl cyanoacrylate, are widely used for vessel embolization and have Food and Drug Administration approval for brain arteriovenous malformations. These products have been used for parent vessel occlusion, either by themselves or as adjuncts to other devices.7 Liquid embolic agents are typically not as controllable as detachable devices like coils, balloons, or plugs. Distal extension or migration of the liquid embolic agents during vessel occlusion can be dangerous when these agents are used in the cerebral circulation or other anatomic sites where distal anastomotic capillary beds must be preserved and protected.
Microcoils and their variations with biological activity, including fibered coils and hydrocoils, can be used for parent vessel occlusion. Coil embolization is a useful technique because it can create targeted and controlled vessel occlusion. However, when occluding larger arteries, such as an ICA or a vertebral artery, the use of numerous coils is often necessary. The problem is compounded when there is high flow through these vessels as seen in the presence of high-flow post-traumatic/iatrogenic fistulas and pseudoaneurysms. The need to deploy multiple coils increases procedure and anesthetic time. Furthermore, the use of multiple coils can quickly escalate the procedural cost, such as in our case number 7. Additionally, an important procedural risk is created by coil embolization that cannot be overlooked. The stepwise progression of vessel occlusion over a long period of time allows slow blood flow through the coil mass interstices. This phenomenon may result in thrombus formation and distal emboli, unless a proximal flow control device such as a temporary balloon is used.
The procedural risk associated with slower and/or stepwise vessel occlusion through coil embolization may possibly be avoided with devices like the AMPLATZER plug or the MVP. The AMPLATZER plug is a resheathable, detachable device designed for precise targeted vessel occlusion and has been used with success.8 However, its use is limited to proximal cervical vessels owing to its slightly stiffer design and inability to track into smaller and tortuous branch vessels. The smallest AMPLATZER vascular plug measures 4 mm in unconstrained device diameter, and requires a minimum of a 4 French system for successful placement. This limits the operator's ability to deploy the device successfully in the intracranial vessels and small head and neck branch arteries.
The MVP complements the available occlusive devices and has many of the benefits provided by the AMPLATZER plug. It has the advantage of being deliverable through a 0.021 or 0.027 in microcatheter. Both of these devices allow for occlusion with a single device that can be resheathed and repositioned as necessary. In our case series, we were able to navigate into small vessels like the proximal sphenopalatine artery (patient 2) or precavernous ICA (patient 7) to deploy the MVP and obtain immediate vessel occlusion. In one case (patient 5), a 0.021 Headway catheter was navigated in a retrograde fashion across the vertebrobasilar junction and down the contralateral vertebral artery to deploy a MVP-3 device to stop retrograde filling of a vertebral artery fistula. In two of our cases (patients 6 and 7), coils were placed distally to the MVP device to avoid anterograde migration. This was done because, at that time, only the 3 mm plug was commercially available and the parent vessel diameter was bigger than the expanded size of the 3 mm plug. The distal coils anchored the MVP. In both cases, the coil mass did not occlude flow and the cessation of flow was only achieved after the MVP was deployed.
To our knowledge, this is the first report documenting the use of the MVP in neurovascular disease. The limitations of this study include its retrospective design, possible selection bias, small population size, and limited long-term follow-up data. However, it illustrates the potential usefulness of this new device and demonstrates early experience with its safety and efficacy in neurovascular applications in appropriately selected patients.
Conclusion
The MVP is a resheathable detachable, PTFE-lined vessel occlusion device that allows for precise placement through a microcatheter. This is the first clinical experience documenting the safety and efficacy of the device in the treatment of neurovascular disease.
Footnotes
Contributors All three authors contributed to writing and editing the manuscript. DG and NBB designed the figures and table. DG and GJ were the primary patient care providers for all patients in this study.
Competing interests GJ and DG have consulting agreements with Reverse Medical.
Ethics approval University of Maryland institutional review board.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Additional patient information may be requested from the senior author, DG, by emailing dgandhi@umm.edu.