K.E.M. Radiology

Video 1: Saccular outpouching arising from the superficial femoral artery with yin yang turbulent flow.

CT lower limb angiography was performed. This demonstrated a saccular pseudoaneurysm from the superficial femoral artery with a narrow neck of of about 2 mm.  (Image 1,2). 

Figure 1: Axial CT angiogram image demonstrating a large pseudoaneurysm from the superficial femoral artery with a narrow neck. There is no thrombus within sac.

Figure 2: Sagittal reformatted CT angiogram i image demonstrating the pseudoaneurysm arising from the superficial femoral artery with compression of SFA. The SFA is well opacified, throughout its course.

Digital subtraction angiography of right lower limb was performed (Image 3, Video 2).

Figure 3:  DSA of the right lower limb demonstrating a Superficial femoral artery pseudoaneurysm with a narrow neck -approximately 2 cm distal to CFA bifurcation 

Video 2: DSA demonstrating jet of contrast filling the pseudoaneurysm via the SFA. 

INTERVENTION TECHNIQUE:

A decision was taken to proceed with ultrasound guided thrombin injection into the pseudoaneurysm. After adequate pre-procedural patient and relative counselling, an informed consent was obtained.

With all aseptic precautions TISSEEL lyophilized fibrin sealant reconstituted (Image 4).

Figure 4:  Fibrin sealant powder and solvent kit. Reconstitution is performed according to colour coding.  Freeze dried sealer protein concentrate in powder form (Blue) to be reconstituted with Fibrinolysis inhibitor solution – aprotinin (Blue).Calcium chloride solution (Black) reconstituted into Freeze dried thrombin powder (Black).

Separate syringes and needles were used for reconstituting sealer protein and thrombin solution. Using blue scaled syringes provided in the kit, fibrinolysis inhibitor solution was transferred into the vial containing freeze dried sealer protein concentrate. The  vial was swirled to ensure freeze dried material is fully soaked. Using black scaled syringes, calcium chloride solution transferred into the vial containing freeze dried thrombin. After the components are fully dissolved , the duploject system pack was opened. Blue scaled and black scaled syringes with needles were assembled. With sterile precautions, sealer protein solution (Blue) and thrombin solution (Black) were aspirated into the respective syringes. The affected site was prepared in a sterile fashion, and local anaesthesia was applied with 2% lignocaine infiltrated into the skin. Under ultrasound guidance, the neck of the pseudoaneurysm was localized and firm compression applied to obliterate the neck. 4 ml of reconstituted sealer protein and thrombin solution was injected into the pseudoaneurysm (Video 3). Persistent flow was observed within the sac after few seconds, hence additional 2 ml reconstituted thrombin injected into the residual sac (Video 4).

Video 3: Ultrasound guided injection of reconstituted thrombin into the pseudoaneurysm. 

Video 4  Additional 2 ml reconstituted thrombin injection injected into the residual sac to achieve complete thrombosis.

Completion ultrasound was performed to confirm the obliteration of flow within the pseudoaneurysm and patent native artery (Image 5, Video 5). 

Figure 5:  Post procedure complete thrombosis of pseudoaneurysm sac.

Video 5  Immediate post procedure complete thrombosis of pseudoaneurysm sac with no flow on colour doppler

After the procedure, 4-6 hrs of bedrest was advised. Follow up ultrasonogram performed after 24 hrs demonstrated complete obliteration of flow within the pseudoaneurysm and patent native superficial femoral artery (Image 6, 7 and 8).

Figure 6:  Follow up ultrasound 24 hrs post procedure showing complete thrombosis of pseudoaneurysm sac.

Figure 7,8:  Follow up ultrasound after 24 hrs post procedure shows complete of obliteration of flow within the sac with patent native superficial femoral artery at and distal to the level of pseudoaneurysm. 

Discussion:

A pseudoaneurysm consists of an outpouching of one ot two vessel wall layers. On the   other hand, a true aneurysm involves all three layers, including the intima, media, and adventitia.

Clinically, it may present with pulsatile hematoma, pain, ecchymosis, or active extravasation. In chronic scenarios, once a fibrous capsule has been formed, it may present with a persistent flow communicating with the arterial lumen. Pseudoaneurysm clinical progression varies; its complications depend on the size, mechanism of injury, duration, patient comorbidities, and neck diameter. Potential complications include expansion, rupture, embolization, extravasation with arterial wall compression, and ischemia. Clinical examination should raise a high index of suspicion   once a pulsatile mass can be felt, especially when a patient reports a recent intervention (3,4,5).

Traditionally, iatrogenic femoral artery pseudoaneurysms caused by endovascular access were treated exclusively by surgical means, but in the last few decades, the paradigm has shifted to less invasive measures. Options for the management of uncomplicated pseudoaneurysms include observation, ultrasound-guided compression, ultrasound-guided thrombin injection, covered stent graft placement and surgical repair. 

Uncomplicated femoral artery pseudoaneurysms less than 2 to 3 cm in diameter may undergo spontaneous thrombosis and regression with observation alone with interval screening, or they can be managed with ultrasound-guided treatments.

Ultrasound guided compression is the initial mode of treatment for femoral pseudoaneurysms. A drawback of this technique is high recurrence rate, studies have shown a recurrence rate of 30% and as high as 41% to 89% in patients receiving anticoagulation therapy. Ultrasound-guided compression has been shown to be less successful in patients with large femoral pseudoaneurysms (> 3 cm in diameter) and who require anticoagulation therapy (6,7).

Indications for percutaneous thrombin injection:

Percutaneous thrombin injection for the management of pseudoaneurysm is indicated when the neck is narrow and failure to achieve haemostasis with ultrasound guided compression.

Contraindications of UGTI included the following:

(1) Patients with known allergy to bovine-derived products

(2) Pseudoaneurysm with rupture, skin necrosis, infection or arteriovenous fistula

(3) Pseudoaneurysm that has already thrombosed

(4) Pseudoaneurysm in which the size of the arterial defect was thought to be larger than the diameter of the affected artery.

Percutaneous thrombin injection for the treatment of post intervention pseudoaneurysm was first reported in 1986 (8). This method was originally performed under angiographic guidance and was later modified to utilize ultrasound guidance as we do today (9,10) and it has become increasingly popular. According to a study of 1,329 cases of UGTI, the primary success rate is very high at 91%–100% (97.5% on average). Although there is a recurrence rate of 0%–9% (3.3% on average), recurrent PSAs can be also treated with a second injection with excellent results. In our case we had two options for the management, one was ultrasound guided thrombin injection and other was graft placement. In this case the neck of pseudoaneurysm was narrow hence ultrasound guided thrombin injection was preferred over graft placement. The graft placement requires additional puncture with subsequent risk of puncture site complications. Another disadvantage with graft placement is need of lifelong anticoagulation.

The overall complication rate from UGTI is 1.3%, including distal embolization, arterial thrombosis, and allergic reactions. Embolization and arterial thrombosis are mostly due to inadvertent puncture of the artery or vein or injection into the neck of the PSA. In this procedure, distal embolization is unlikely to happen. This is because thrombosis only occurs when a high concentration of thrombin mixes with relatively stagnant blood and thrombin at the PSA site, and if thrombin were somehow to leak into the artery, it would be effectively diluted in the circulating blood and neutralized by the anticoagulant factors such as antithrombin III and thrombomodulin (11). However, this is not the case when a large volume of thrombin is administered rapidly into the native artery. Therefore, precise placement and constant visualization of the tip of the needle, slow and incremental injection of thrombin, and avoiding excessive dosage amounts are indispensable. Severe allergic reaction after thrombin injection is extremely rare (12).

Balloon inflation at the site of the neck of a PSA in order to prevent leakage of thrombin into the artery has also been described (13), an additional puncture is necessary to do this, and we generally avoid this to limit the risk of further bleeding complications.

Conclusion: 

Ultrasound guided thrombin injection for femoral pseudoaneurysm can be considered as quick and effective treatment option. It is simple and has lesser complications as compared to surgical treatment. Wherever feasible, US guided thrombin injection can be considered as the treatment of choice for femoral pseudoaneurysms.

References:

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