Carotid artery free-floating thrombus (FFT) is a rare but clinically significant cause of embolic stroke. Treatment has historically been confined to carotid surgery or best medical therapy, with neither option proved to be superior. However, recent advancements in endovascular interventions have heralded a new age of innovative management strategies for vascular disease. We present three distinct cases of stroke secondary to carotid artery FFT, successfully treated with stent retriever endovascular thrombectomy.
- interventional neuroradiology
- large vessel occlusion
- free floating thrombus
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- interventional neuroradiology
- large vessel occlusion
- free floating thrombus
Carotid artery free-floating thrombus (FFT) is a rare but clinically significant cause of embolic stroke. As endovascular thrombectomy (EVT) establishes itself as the best method of managing proximal anterior circulation acute ischaemic stroke, increasing procedural experience has led to an expansion of its potential applications.1 2 We present a series of cases encountered over 3 months in which stent retriever EVT was used to treat non-occlusive intraluminal carotid artery FFT following acute and subacute embolic stroke presentations
A 54-year-old woman attended the outpatient stroke service with recent cerebral embolic events. Previous medical history included deep vein thrombosis (DVT) and unprovoked pulmonary emboli. The patient was taking rivaroxaban 20 mg daily for recurrent unprovoked pulmonary emboli.
Five months previously, the patient had been admitted with acute stroke. MRI at that time demonstrated multifocal acute embolic infarcts in the left parieto-occipital region and CT angiography (CTA) showed a mural thrombus with a tiny FFT component in the left internal carotid artery (ICA) (figure 1A). A planned carotid endarterectomy was cancelled, pending investigation for coagulopathy. The patient was treated with low molecular weight heparin (LMWH) and aspirin. Repeat carotid Doppler ultrasound and CTA 3 weeks later showed a reduction in thrombus size. The patient was discharged home on day 17 with warfarin in place of preadmission rivaroxaban. No malignancy or thrombophilia was identified.
At outpatient consultation, a 3-week history of progressive dysphasia was noted, and the patient reported an episode of right-sided facial weakness lasting approximately 9 hours. MRI demonstrated new infarcts in the same territory as previously affected, and CTA identified recurrence of left ICA FFT, now 3.2 cm long (figure 1B).
Intravenous unfractionated heparin was started. However, no significant thrombus reduction was shown on follow-up imaging 2 days later and the patient proceeded to undergo EVT (figure 1C and D). An elongated, pale-coloured clot was successfully retrieved (figure 2). Carotid Doppler ultrasound performed 1 week after the intervention demonstrated no residual thrombus. MRI of the brain showed temporal evolution of the known parietotemporal infarct with no interval extension or new infarction. The patient was discharged on day 18, 2 weeks after EVT, with diagnosis of likely seronegative antiphospholipid syndrome. No further events were seen at a 4-month follow-up.
A 39-year-old woman presented with a 9-hour history of left-sided weakness and facial droop. Examination disclosed a left-sided hemi-spatial neglect. National Institute of Health Stroke Scale (NIHSS) score was 8.
The patient was a homeless active intravenous drug user with known HIV and positive for hepatitis C. She had had three previous episodes of lower limb DVT, the most recent diagnosed 7 days previously. Therapeutic LMWH was prescribed, but compliance was poor.
A non-contrast CT brain scan showed a small hypodense focus in the right frontal lobe and established left parietal and left cerebellar infarcts. CTA demonstrated a non-occlusive FFT in the right cervical ICA with mural attachment (figure 3A) but no distal intracranial occlusion.
The patient was outside the therapeutic window for intravenous thrombolysis and underwent EVT, with successful retrieval of thrombus (figure 3B and C). An MRI brain scan performed 1 day after EVT demonstrated an acute right frontal lobe infarct and punctate right occipital infarcts. Echocardiogram showed a patent foramen ovale.
The patient was discharged to a step-down unit 10 days after EVT, with improved left upper limb power.
An 80-year-old man presented with an 8-hour history of dysphasia. Examination yielded global aphasia and right-sided hemispatial neglect. NIHSS score was 6. Relevant medical history included recent colorectal carcinoma, and lower limb DVT 2 months previously, managed with ongoing therapeutic LMWH.
CTA disclosed non-occlusive FFT in the left common carotid artery (figure 4A). Given the occurrence of FFT despite compliance with therapeutic anticoagulation, a decision was made to proceed directly to EVT, and the thrombus was successfully retrieved (figure 4B–D). Aspirin 75 mg was started and therapeutic LMWH continued, with good neurological recovery and a 24-hour NIHSS score of 1.
Follow-up investigation revealed a new diagnosis of transitional cell cancer of the left kidney as the likely aetiology. The patient was subsequently transferred to a urology centre for laparoscopic nephrectomy, with no further ischaemic events.
Through a right common femoral artery approach an 8 Fr balloon guide catheter (MACH1 8Fr, Boston Scientific) was placed in the left common carotid artery (CCA), avoiding contact with the thrombus, the origin of which was proximal in the ICA. An Emboshield filter (Emboshield NAV embolic protection system, Abbott Vascular) was advanced (without balloon inflation) distal to the thrombus so as to prevent distal thrombus migration. A 6×30 stent retriever (CATCH+MAXI, Balt Extrusion) was advanced, deployed distal to the thrombus. With the guide catheter balloon inflated, the stent retriever was withdrawn, using syringe suction to retrieve the thrombus with one pass. We use 2×60 mL luer lock syringes (VacLok pressure syringes, Merit Medical) attached to two three-way stopcocks (Marquis Series stopcock, Merit Medical) on the flush line attached to the rotating haemostatic valve (Stryker Corporation) on the guide catheter as our standard method of aspiration. Selective angiography after stent retrieval demonstrated successful removal of the thrombus with no residual stenosis. There were no immediate complications and the patient was transferred back to the referring hospital on the same day.
Again, using an 8 Fr balloon guide catheter (Flowgate2 balloon guide catheter, Stryker Corporation) in the right CCA, an Emboshield filter device (Emboshield NAV6 embolic protection system, Abbott Vascular) was positioned beyond the thrombus in the ICA. A 6×30 stent-retriever (CATCH+MAXI, Balt Extrusion) was deployed and the clot was retrieved. The balloon was inflated for clot retrieval as for intracranial thrombectomy and syringe aspiration applied during retrieval. Post-thrombectomy digital subtraction angiography showed persistent sluggish flow in a left M2 middle cerebral artery branch with no new occlusions. There were no immediate complications and total procedure time was 33 min.
Through a standard femoral approach an 8 Fr balloon guide catheter (Flowgate2 balloon guide catheter, Stryker Corporation) was placed proximally in the CCA, which contained the thrombus. The Emboshield filter device (Emboshield NAV6 embolic protection system, Abbott Vascular) was deployed in the proximal ICA. A stent retriever (EmboTrap II 5×33, Neuravi) was deployed and a large volume of thrombus retrieved with the balloon inflated and with syringe aspiration. A second pass was performed with the same technique and a further small clot was retrieved.
Arterial FFT is an uncommon condition, defined as an elongated thrombus attached to an arterial wall, with circumferential blood-flow at its distal end and cyclical motion relating to the cardiac cycle.3 4 Few publications have discussed FFT, with evidence limited to case reports and series.
Overall incidence is estimated to be 0.05–1.5%.3 5–8 FFT typically presents acutely, although subacute presentations have been observed.9 Atherosclerosis is the most commonly associated aetiology,4 10while a relationship to hypercoagulability has also been identified.3
Embolic phenomena are common in cases of FFT, conferring a high risk of recurrent ischaemic events.9 10 This mandates careful consideration of the optimal treatment approach. However, owing to the rarity of such cases, standardised treatments have not been defined. Management is selected on a case-by-case basis, with medical, surgical and endovascular treatments reported.3 Surgical endarterectomy or embolectomy was previously accepted as the definitive management,4 7 11 12 but some technical points should be considered carefully. For example, in case 1, the vascular surgeons considered the risk of embolic complication too high and EVT was preferred.
FFT has also been successfully managed medically, with anticoagulation and/or antiplatelet therapy.10 13 However, given reported patient variation in response to anticoagulation, further intervention may be required.9 14 Medical treatment was unsuccessful for our first case, and the well-organised nature of the clot in this case indicates that certain clots may not fully resolve over time, resulting in persistent risk of embolic events and reduced likelihood of response to tissue plasminogen activator.
Endovascular intervention has recently been shown to be an effective management strategy for FFT.14 15 Previously described endovascular procedures include carotid angioplasty and stenting,16 with EVT reserved for acute ischaemic stroke.2 However, increasing procedural experience and evolution of techniques has established EVT as a potentially effective intervention, with successful case reports described.14 Our cases further highlight the potential for stent retriever EVT in the management of carotid artery FFT, notably in both acute and subacute presentations. In all three of our cases, patients had cerebral embolic events while receiving anticoagulation therapy, demonstrating the potential need to escalate management from medical therapy.
EVT also offers certain advantages over surgery: shorter procedure time and minimal vascular manipulation, while still affording the opportunity for en bloc elimination of the thrombus.14 General anaesthesia is not required and anticoagulation may be continued in the periprocedural period if necessary. Using a combination of techniques which have evolved from other endovascular interventions, such as distal filter device deployment, proximal balloon occlusion and use of stent-retrievers, this option may be considered relatively controlled, minimising the risk of embolic complications. If an embolus or a clot fragment is carried into the intracranial circulation, intracranial EVT may be attempted immediately.
As the role of EVT in managing acute ischaemic stroke has evolved, increasing procedural experience has led to a broadening of its application. We demonstrate that stent retriever EVT is a safe, effective treatment for selected cases of FFT, minimising the risk of devastating embolic consequences.
The author’s wish to thank Sinead Duff, Chloe Carpenter and Nicola Cogan for their contribution to this projectand continued support.
Contributors NF: lead author, collected and reported details of cases 1 and 3, drafted and revised the manuscript, approved submitted version and agrees to be accountable for all aspects of the work. RM: drafted and revised the manuscript, approved submitted version and agrees to be accountable for all aspects of work. BG: collected and reported details of case 2, revised the manuscript, approved submitted version and agrees to be accountable for all aspects of work. SD: performed data analysis, approved submitted version and agrees to be accountable for all aspects of work. SM, DR, PO’B: senior authors, advised on service implementation, advised and revised the manuscript, approved submitted version and agree to be accountable for all aspects of the work. JT: senior author, implemented and directed service, acquired data, advised and revised the manuscript, approved submitted version and agrees to be accountable for all aspects of the work.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests SD’s data collection was partially funded by Neuravi, Ltd, as part of a wider research project with the Galway-Mayo Institute of Technology.
Patient consent Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
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