Successful treatment of superior vena cava syndrome with mechanical thrombectomy following failed thrombolytic therapy

INTRODUCTION

Superior vena cava syndrome (SVCS) is a symptomatic response to obstruction of blood flow through the superior vena cava (SVC), often caused by thrombus formation. Thrombosis can result from compression of the SVC from a mediastinal mass or iatrogenic causes, including semipermanent intravascular catheters.^[1] Symptoms frequently include swelling of the face and neck, dyspnea, cough, and distended collateral veins in the chest.^[2]

Typical endovascular treatments for SVCS include thrombolysis, venoplasty, or stenting, either independently or in conjunction.^[2] However, these treatment options each have their limitations. Thrombolytics can dissolve fresh thrombus but are less effective on more organized thrombus. They require long infusion times and can carry significant bleeding risks.^[3,4] Conversely, venoplasty and stenting do not remove thrombus but instead force the thrombus aside to create a flow channel. Furthermore, stenting inherently requires the placement of a permanent implant, which may not be suitable in certain veins and can be prone to reocclusion in as many as 10.5% of SVCS patients.^[5] When endovascular therapies fail or are not possible, patients may be relegated to invasive and morbid surgical reconstruction.^[2,6]

A thrombectomy method tailored to extract thrombus of various chronicities could provide an alternative therapeutic approach for SVCS. The InThrill thrombectomy system (Inari Medical, Irvine, CA) is a thrombolytic-free mechanical thrombectomy device designed to capture and remove acute to chronic thrombi from 4 to 10 mm vessels. The 8-French (Fr) system consists of a sheath with a recapturable braided funnel and a thrombectomy catheter with a self-expanding nitinol coring element [Figure 1].

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Figure 1:

Image of the InThrill thrombectomy system. Image courtesy of Inari Medical.

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We present a case of SVCS with extensive, acute on chronic thrombosis of the bilateral brachiocephalic, subclavian, and axillary veins, that was successfully treated with InThrill following inadequate recanalization with thrombolysis and venoplasty.

CASE REPORT

A 58-year-old woman with diabetes mellitus, hypothyroidism, and metastatic breast cancer on chemotherapy presented to the emergency department with 2–3 weeks of progressive face, neck, and upper extremity swelling. She also reported dizziness, shortness of breath, and purple-red discoloration of the face and upper chest. Duplex ultrasound identified acute thrombus in both internal jugular, subclavian, and axillary veins. Computed tomography (CT) ruled out pulmonary embolus but demonstrated bilateral brachiocephalic vein thrombosis as well as thrombus in the SVC associated with the tip of her right chest port catheter.

Initially, the patient began to improve following conservative treatment with chest port removal and anticoagulation. However, 9 days after the presentation, her symptoms began to worsen, and endovascular therapy was pursued.

Venography through bilateral basilic vein access demonstrated occlusion of the SVC as well as the bilateral brachiocephalic and subclavian veins and the left axillary vein [Figures 2a and b]. Catheter-directed thrombolysis (CDT) was initiated with catheters through each access site, both infusing 0.5 mg alteplase/h, with 500 U heparin given/h systemically.

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Figure 2:

A 58-year-old woman with diabetes mellitus, hypothyroidism, and metastatic breast cancer on chemotherapy presented to the emergency department with 2–3 weeks of progressive face, neck, and upper extremity swelling. (a and b) Imaging demonstrated occlusion of the superior vena cava as well as the bilateral brachiocephalic and subclavian veins and the left axillary vein. (c and d) Following overnight catheter-directed thrombolysis, venography demonstrated irregularities indicative of persistent chronic thrombus, including collateral branch filling (black arrow), a distinct shift in contrast opacity to thread-like channels (box), and contrast filling defects (white arrows). (e and f) Post-thrombectomy venography showed significant luminal gain and brisk flow.

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Following overnight thrombolysis, venography demonstrated recanalization of a narrow flow channel on each side, however despite aggressive venoplasty, a significant burden of organized thrombus remained, which severely limited flow [Figures 2c and d]. Given bilateral subclavian involvement precluding stent placement, the decision was made to attempt mechanical thrombectomy.

An 8 Fr InThrill sheath was exchanged into the left basilic access site, and the InThrill catheter was advanced into the right atrium. After careful unsheathing of the coring element precisely at the superior cavoatrial junction, two passes with the device removed thrombus from the left upper extremity and central veins. The InThrill sheath and catheter were then transferred to the contralateral side, and in a similar fashion, three passes returned an organized thrombus from the right upper extremity and central veins. Post-thrombectomy venography showed significant improvement in thrombus burden, and following prolonged venoplasty, there was significant luminal gain and brisk flow without requiring stents [Figures 2e and f]. Extracted thrombus following one pass with the InThrill catheter is shown in Figure 3. The patient tolerated the uncomplicated procedure and continued therapeutic anticoagulation immediately. She experienced rapid improvement in symptoms and was discharged 3 days following thrombectomy on enoxaparin, which was later transitioned to apixaban. She continues to do well at 15 months of follow-up.

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Figure 3:

Image of the InThrill coring element with thrombus following one pass through the occluded segment. Additional extirpated material was not photographed.

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DISCUSSION

This is the first reported use of InThrill for treating SVCS, a debilitating condition with a challenging treatment algorithm. While this patient’s symptoms developed insidiously, SVCS often presents acutely, rendering it a medical emergency due to its associated morbidity and mortality. Given the patient’s relatively mild symptoms at presentation, she was treated conservatively with anticoagulation therapy and chemotherapy chest port removal. Hypercoagulability from malignancy combined with the presence of a chest port likely instigated thrombosis. Conservative management resulted in initial symptom improvement. When symptoms worsened 9 days following symptomatic presentation, primarily acute thrombus was expected, prompting the use of thrombolytic therapy. However, CDT resulted in only partial restoration of flow despite overnight infusion and revealed the presence of a significant organized thrombus, which was resistant to aggressive venoplasty. These findings align with the observation that venous thrombus is often more chronic than predicted by symptom duration alone.^[7] Unsuccessful CDT for SVCS is not uncommon; a retrospective study reported a <25% success rate when CDT was performed more than 5 days after symptom onset.^[8]

When endovascular therapies prove unsuccessful or unviable, patients may face invasive surgical reconstruction procedures.^[2,6] In the case presented here, despite employing anticoagulation, CDT, and aggressive venoplasty, only partial restoration of flow was achieved due to the presence of an organized thrombus. In addition, stent placement was not a viable option due to bilateral subclavian involvement, thus exhausting conventional endovascular options. Residual vein obstruction following treatment is a known risk factor for rethrombosis, underscoring the importance of complete thrombus removal.^[9] The addition of novel tools to the endovascular armamentarium that can remove acute to chronic thrombus may provide additional minimally invasive treatment methods for SVCS before resorting to surgical interventions.

InThrill is indicated for the removal of thrombi and emboli from peripheral vessels from 4 to 10 mm in diameter and is commonly used for dialysis access management.^[10-12] In this case, it was the mechanical thrombectomy device of choice due to its favorable size, which allowed for easy basilic vein access to treat all thrombosed segments, as well as the device’s ability to engage organized thrombus. While the ClotTriever and FlowTriever thrombectomy systems (Inari Medical, Irvine, CA) have been successful in treating thrombosis of the SVC, they are not optimally sized for basilic vein access and thrombectomy of the axillary veins required in this case due to the small vessel anatomy and extent of thrombosis.^[13,14]

Thrombectomy with InThrill efficiently removed acute to chronic thrombus with negligible blood loss, no complications, and no additional thrombolytics. The complete restoration of flow through this non-invasive method obviated the need for surgical intervention. Uninterrupted flow and complete symptom relief were maintained through 15-month follow-up.

While the outcome of this case is promising [Figure 2], the use of intravascular ultrasound and vessel pressure measurements pre- and post-procedure may have provided further insight into the effectiveness of intervention with InThrill. Although a post-procedural CT of the pulmonary arteries is not standard practice when symptomatic pulmonary embolism is not observed, as in our case, it could have verified the absence of embolization following mechanical thrombectomy.

CONCLUSION

This case highlights a new use of the novel InThrill thrombectomy system for the treatment of SVCS. Maintained patency and symptom resolution through 15-month follow-up was achieved through thrombectomy of organized thrombus following failed thrombolytic therapy. With further study, single-session mechanical thrombectomy may prove to be a first-line treatment option for SVCS.