Iatrogenic Vertebral Arteriovenous Fistula Involving Brachiocephalic Vein Due to Central Venous Catheterization: A Case Report

Introduction

Vertebral arteriovenous fistula (VAVF) is a rare vascular entity characterized by abnormal connections between the extracranial vertebral artery (VA) or its branches and adjacent veins.^1–11 The most common cause of VAVF is trauma, including iatrogenic injury. Central venous catheterization (CVC) is one of the main causes of iatrogenic trauma, and several cases of iatrogenic VAVF after CVC have been reported.^1–14 CVC-induced VAVF (CIVAVF) often involves the internal jugular vein (IJV) or vertebral vein (VV) and no cases of CIVAVF involving brachiocephalic vein (BCV) have been reported. The most frequent symptom of CIVAVF is pulsatile tinnitus, but it can be complicated by motor and/or sensory paresis due to cervical myelopathy or radiculopathy, depending on the flow velocity of the shunt or venous drainage pattern. No guidelines currently exist for the treatment of CIVAVF. Here, we report a case of CIVAVF involving BCV that showed no symptoms other than a vascular murmur. To the best of our knowledge, this is the first case report of CIVAVF involving BCV.

Case Report

A 79-year-old female was referred for assessment of a VA aneurysm at the V1 segment. She had undergone open-heart surgery 20 years previously, when CVC was performed via the right IJV. Physical examination revealed a vascular murmur on the right side of her neck. No neurological deficits were found. Computed tomography angiography showed a large enhancing structure with abnormal connections with the V1 segment of the right VA and the right BCV in the arterial phase (Figure 1A–D). Right vertebral angiography revealed a high-flow shunt from the V1 segment of the right VA, draining into the right BCV at the C7-Th1 cervical level. The fistula had a single communication between a pseudoaneurysm and large varix (Figure 2A). No retrograde venous drainage was apparent into the right IJV, VV, or subclavian vein. The right VA was dilated, and the flow of the right VA beyond the fistula was antegrade, and no collateral flows had developed. Left vertebral angiography showed no steal flow into the fistula (Figure 2B). We diagnosed a CIVAVF involving the right BCV and performed an endovascular obliteration of the shunt to prevent a variceal rupture.

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Figure 1.

Computed tomography angiography. (A) A pseudoaneurysm (white asterisk) arose from the V1 segment of the right vertebral artery (VA) (white arrow). (B, C, D) A large varix (black asterisk) was located just after the shunt hole (white arrowhead), drained into the right brachiocephalic vein (white dotted arrow) after the junction of the right internal jugular vein (white arrows), and subclavian vein (white dotted arrows).

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Figure 2.

Digital subtraction angiography. (A) Right vertebral angiography showed a pseudoaneurysm (white arrow) arising from the V1 segment of the vertebral artery (VA) and just proximal to the shunt hole (black arrow). A large varix (white asterisk) was just distal to the shunt hole and drained into the right brachiocephalic vein (black asterisk). The distal flow of the VA was not poor, and no collateral flows developed. (B) Left vertebral angiography showed no steal flow into the fistula.

We planned to treat the shunt with selective transarterial and transvenous coil embolization of the pseudoaneurysm under flow control using a balloon catheter. With the patient under local anesthesia, a 7-French guiding catheter was introduced and its tip was navigated into the V1 segment of the right VA via the right femoral artery. A 6-French guiding catheter was then introduced, and its tip was navigated into the varix via the left femoral vein (Figure 3A). Via the arterial 7-French guiding catheter a microcatheter was navigated into the pseudoaneurysm and a balloon catheter was also advanced to the V1 segment of the right VA. Via the venous 6-French guiding catheter, another microcatheter was navigated into the pseudoaneurysm across the shunt hole. (Figure 3B). Under transarterial flow control with balloon inflation, 14 detachable coils were placed in the pseudoaneurysm by transarterial and transvenous approach (Figure 3C). The shunt flow was still apparent but significantly reduced just after the treatment (Figure 3D) and completely resolved the vascular murmur. Postoperative magnetic resonance imaging showed no findings of thromboembolic infarctions, and the patient was discharged 7 days after the endovascular procedure without any neurological deficits. Six months after the embolization, right vertebral angiography showed complete obliteration of the shunt (Figure 3E).

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Figure 3.

Intraoperative and postoperative images. (A) A 7-French guiding catheter was navigated into the V1 segment of the vertebral artery (VA), and a 6-French guiding catheter was navigated into the varix. (B) Coils were placed in the pseudoaneurysm under flow control in VA. (C) The balloon was deflated after the coil placement. (D) The shunt flow was still apparent but significantly reduced just after the treatment. (E) Six months after the treatment, the shunt flow had completely disappeared.

Discussion

The etiology of VAVF is classified into 2 groups: traumatic and spontaneous.^1–6,10 Traumatic VAVFs are mainly related to blunt traumas, penetrating traumas including stab injuries and gunshot injuries, and iatrogenic injuries.^1–11,13,14 The causes of iatrogenic injuries have often been reported as CVC and surgeries such as fixation of the upper cervical spine.^1–14 A VAVF can develop due to the proximity of the VA to adjacent veins. ⁵ When a VA and adjacent vein are injured simultaneously or a traumatic post-injury VA pseudoaneurysm subsequently ruptures, arterial bleeding from the VA or pseudoaneurysm drains into the nearest lower pressure vein, followed by the formation of an AVF. ⁵

Any traumatic causes of vertebral artery injuries (such as stab wound and arterial puncture due to CVC) can be complicated by VAVF formation. A 3% incidence of arterial puncture during IJV catheterization was described. ¹⁵ We have found no reports concerning the incidence of VA injury due to CVC. Although the actual incidence of CIVAVF is unclear, there are likely many cases, as these types of fistulae are sometimes asymptomatic and remain undiagnosed.^{3,4,7,8,10,12–14} Traumatic VAVF often occurs above the V2 segment of the VA,^2,3 whereas CIVAVF often occurs in the V1 segment of the VA.^5–7,12 In part since the site of the lesion in CIVAVF cases has been often identified and since our patient had no history of trauma other than the CVC, we were able to diagnose her CIVAVF involving a BCV.

Approximately 30% of patients with VAVF are asymptomatic. ³ Tinnitus is the most common symptom of a VAVF. In some patients, the VAVF may cause heart failure because of an increased preload volume.^4,5,7,14 Neurological symptoms are often associated with the velocity of the shunt flow and the venous drainage pattern. ³ High-flow shunts increase the blood volume through the fistula and lead secondarily to arterial steal, resulting in vertebrobasilar insufficiency.^4,7

High-flow shunts can also cause retrograde venous drainage (RVD). RVD into the IJV sometimes causes a reduction in the returning venous circulation from the brain, followed by intracranial hypertension. When RVD into the VV or vertebral venous plexus (VVP) occurs in VAVF cases, the VVP or epidural vein can become dilated, followed by venous hypertension or cervical myelopathy.^4,5,7 Dilated epidural veins can mechanically compress the radicular nerves, leading to cervical radiculopathy.^4,5,7 Our patient’s case involved a high-flow shunt but no arterial steal or RVD, and she had presented with no neurological symptoms or other symptoms. It is essential to note that a VAVF with RVD into the VV or VVP can be diagnosed at an early stage due to neurological manifestations of the cervical cord or nerve root. However, a VAVF without RVD is often asymptomatic and likely to be undiagnosed for a long period, as in our case.

The VAVF in the present patient also contained a large pseudoaneurysm and varix between the right VA and BCV across a shunt hole. Pseudoaneurysms are often caused by direct injury due to penetrating trauma or by arterial dissection due to mechanical or iatrogenic trauma. A VAVF sometimes occurs concomitantly with venous varices or ectasia of the affected veins, especially when the velocity of the shunt flow is high and the shunt causes RVD.^7,10 However, the pathophysiology of variceal formation is unclear. It is possible that in our patient, the chronicity of the lesion concomitant with the high-flow shunt was associated with a gradual enlargement of the pseudoaneurysm and varix and a subsequently increasing rate of secondary rupture. More studies are needed to establish the natural history, pathophysiology, and angioarchitecture of CIVAVFs involving a BCV.

No guidelines are currently available for the treatment indications for VAVF. Because of the high risk of surgical complications, surgical treatment is rarely indicated. Endovascular treatment is less invasive than surgery (due to the endovascular devices and techniques) and is considered a safe and reliable method.^8,11 We selected an endovascular treatment for our patient, to obliterate the shunt for the prevention of variceal rupture.

In endovascular treatments of VAVF, constructive treatment is generally recommended rather than deconstructive treatment in case in which the parent artery can be preserved. When a high-flow fistula lacks sufficient space to contain embolic agents, or when the parent artery has unfavorable anatomy (ie, it is small, diseased, or tortuous), constructive therapy is often difficult. ⁷ In such situations, deconstructive treatment can be selected, even if not recommended. However, if the contralateral VA is hypoplastic or exhibits reduced flow, deconstructive therapy is not possible. ⁹ Recent studies have reported that endovascular treatment using a covered stent is effective for a VAVF because it allows preservation of the parent artery.^7,13,14 However, covered stents are not approved for neuroendovascular interventions in Japan, and this treatment requires antiplatelet therapy. Our patient’s pseudoaneurysm developed sufficiently and we were able to successfully obliterate the fistula and preserve the right VA by the selective embolization of the pseudoaneurysm under flow control, without the use of any antiplatelet drugs. This case demonstrates that endovascular treatment can be feasible and effective for a CIVAVF involving a BCV.

Conclusion

A CIVAVF involving a BCV is extremely rare. Since it does not involve arterial steal or RVD, it can manifest no neurological and other symptoms and can be undiagnosed for a long period. Although the long-term outcome of such case is unclear, selective embolization of the shunt can be a feasible and useful option for the management of a CIVAVF involving a BCV.