Mechanical embolectomy of a large iliocaval fat embolus

Abstract

While fat emboli are often small and predominantly impact capillary beds, larger fat emboli can pose a substantial risk of pulmonary embolism. This case demonstrates the management of a large iliocaval fat embolus using endovascular mechanical thrombectomy techniques. The Inari Protrieve and RevCore systems were successfully used to extract a large fat embolus in an 87-year-old woman who had undergone a recent hip surgery.

Fat embolism syndrome is a rare but potentially life-threatening clinical diagnosis that can occur in the setting of trauma and after orthopedic operations. Fat globules are commonly detected after femoral fractures,¹ with clinical fat embolism syndrome occurring in approximately one in nine patients with long bone or hip injuries.² Although the pathogenesis is incompletely understood, the mechanical theory proposed by Gauss in 1924 hypothesizes that an increased intramedullary pressure results in adipose tissue extrusion from the marrow into venous structures and then embolizing systemically.³

The endovascular management of fat embolism has been described in the setting of cerebral embolectomy⁴; however, there is a paucity of literature on its management in the systemic circulation. Fat emboli can contain adipose tissue, bone marrow, and inflammatory reactants, in contrast to thrombotic material seen in deep venous thrombosis, which inferior vena cava (IVC) filters and anticoagulation are designed to treat.⁴ Because of this discrepancy, traditional approaches to thromboembolism treatment, such as IVC filter placement, the use of snares, and anticoagulation, are likely inadequate for the treatment of fat embolus. Modern mechanical thrombectomy techniques have expanded at a rapid pace, with newer devices using aspiration and coring for safe endovascular extraction.⁵

Here, we present the case of an 87-year-old woman with a large iliocaval fat embolus after hip surgery, which was managed using modern endovascular techniques.

Case report

An 87-year-old woman presented with abdominal pain, fatigue, and bloody stools 2 weeks after left hip arthroplasty for hip fracture. Computed tomography scan was obtained for workup and incidentally demonstrated a large, hypoattenuating filling defect in the distal IVC, extending into the left common, external, and internal iliac veins (Fig 1).

Fig 1.

Coronal (A) and axial (B) views of the fat embolus on computed tomography scan with the lesion demarcated by white arrows.

The filling defect was suspected to be a fat embolus in the setting of recent hip surgery. Although an incidental finding, because of its large size, location, and risk of further embolization, we recommended urgent embolectomy. The patient’s guardian consented to the usage of her case and images in this report.

Operative technique

The right internal jugular vein was accessed under ultrasound guidance. An Amplatz wire (Boston Scientific) was advanced into the distal IVC, followed by serial dilation and placement of a 20 Fr Protrieve Sheath (Inari Medical). The device’s mesh funnel was then deployed in the IVC for embolic protection. A venogram was performed, confirming the presence of a large, organized lesion in the left iliac veins extending into the distal IVC (Fig 2).

Fig 2.

Intraoperative venogram demonstrating filling defects in the left iliac veins and inferior vena cava (IVC). The Protrieve’s mesh funnel can be seen abutting the IVC walls.

The lesion was crossed with a glidewire and an angled glide catheter. The glidewire was exchanged for an Amplatz wire, and the Triever 20 (Inari Medical) sheath tip was positioned proximal to the embolus. Minimal organized embolus was aspirated, and small, oily-appearing particles were visualized in the aspirated material. Given this finding, the decision was made not to recirculate the aspirated blood through the sheath.

A large filling defect remained on venography. The FlowTriever XL (Inari Medical) catheter was introduced. The discs were passed across the embolus multiple times while aspirating to macerate and mobilize the embolus. A venogram demonstrated moderate reduction in embolus burden, although it appeared as though the majority of the embolus had migrated proximally to the mid segment of the infrarenal IVC. We then used intravascular ultrasound (IVUS) to better characterize the lesion. IVUS demonstrated resolution of the iliac embolus, but an organized embolus was present in the infrarenal IVC, concerning for embolus migration.

The RevCore thrombectomy catheter (Inari Medical) was then introduced. The RevCore coring element was advanced distal to the embolus and retracted through it while rotating to core the lesion (Fig 3).

Fig 3.

RevCore coring element used to mobilize the embolus.

After using the RevCore, IVUS confirmed a large amount of embolus seated at the Protrieve sheath’s mesh funnel. Under IVUS visualization, the embolus was aspirated into the sheath. Completion venogram and repeat IVUS demonstrated a widely patent IVC and iliac system (Fig 4).

Fig 4.

Completion venogram demonstrating patent distal inferior vena cava (IVC) and left iliac veins.

On the backtable, the Protrieve sheath was flushed, producing a large, organized embolus (Fig 5). Histopathology confirmed a fat embolus with organized changes. The access site was closed with the FlowStasis (Inari Medical) retention device. The patient tolerated the procedure well, with an estimated 250 mL total blood loss as the fat-containing blood was not recirculated. She had an unremarkable postoperative recovery. Her abdominal pain and bloody stools resolved, and she was discharged on postoperative day 2 with outpatient gastroenterology referral for further workup. She was continued on a 4-week course of subcutaneous heparin for prolonged immobilization after orthopedic surgery. At 1-month follow-up, duplex ultrasound demonstrated patent IVC and iliac veins with phasic flow and no evidence of residual filling defect.

Fig 5.

A large, organized fat embolus aspirated from the Inari Protrieve sheath.

Discussion

Fat emboli are a common finding after major orthopedic surgeries and trauma.⁶ Although no formal treatment guidelines exist for organized macro fat emboli management, treatment options include albumin infusion for intravascular free fatty acid binding and IVC filter placement.⁷ Anticoagulation with heparin has been proposed, given its ability to stimulate lipase activity, but is not used in clinical practice due to increased risk of bleeding with no obvious benefit.⁸ These are all reasonable options in a patient of this age, but given the recency of the inciting event, the radiographic appearance, and concern for possible further embolism, we recommended intervention to attempt emboli retrieval. In addition, given the obvious fatty aspirate and pathology consistent with fatty emboli, we opted to postoperatively continue the patient’s deep venous thrombosis prophylaxis rather than anticoagulate the patient for this pathology.

Organized IVC fat embolism is rare, with only one case reported in the past decade.⁹ In contrast to their approach, which used an IVC filter and snare to capture embolic material, we used the Protrieve sheath, which offers both working access and embolic protection.¹⁰ The sheath’s mesh funnel effectively trapped large fatty particles, and smaller fragments were captured during aspiration. Given the inflammatory potential of fat microemboli,¹¹ minimizing their release is critical, and IVC filters may not be sufficient. Although the embolus was adherent to the cava wall, aspiration attempts near the embolus yielded fatty-appearing particulate, which is concerning for microembolism from the lesion. Given the oily appearance of aspirated blood, we recommend against reinfusion because of theoretical concern for systemic inflammatory response.¹

The technical challenge of managing a fat embolus became immediately apparent upon engaging the Inari FlowTriever’s discs. The FlowTriever’s discs had limited effect, deforming around the embolus with minimal mobilization. The RevCore’s technical success was likely due to its larger, stiffer coring element.¹² Future cases may benefit from starting with stiffer thrombectomy devices.

An additional technical pearl of this case includes the use of IVUS. IVUS allowed for clear delineation of the embolus extent and characterization of its morphology, and enabled direct visualization of the embolus extraction. This is in alignment with its reported benefits in the management of venous thromboembolism.¹³

Conclusion

This case illustrates the successful use of current generation thrombectomy devices, including the Protrieve sheath and RevCore, for removing an organized fat embolus. Early use of IVUS is critical. Modern thrombectomy technology offers an effective option for managing this rare pathology.

Funding

None.

Disclosures

None.

From the Society for Vascular Surgery