Femoral Artery Pseudoaneurysm

Femoral artery pseudoaneurysm is a contained collection of blood outside the arterial wall that communicates with the femoral artery lumen. It is the commonest vascular complication of femoral access and can expand, rupture, compress adjacent structures or embolise.

After diagnostic catheterisation it occurs in about 0.05 to 0.5%, and after percutaneous coronary intervention in about 0.5 to 2%. Rates are higher with systematic duplex screening, large sheaths, structural heart and endovascular procedures (up to about 6% with large bore access), and use of anticoagulants and antiplatelets.

Risk factors are a puncture distal to the femoral head (superficial femoral or profunda femoris artery) or proximal to the inguinal ligament, a large sheath, obesity, female sex, older age, hypertension, a calcified artery, peripheral arterial disease, inadequate compression after sheath removal, and drug injection into the groin.

Spontaneous thrombosis occurs in many small pseudoaneurysms, especially those under 2 cm. Infection (mycotic pseudoaneurysm) occurs with groin injection and after prosthetic graft surgery.

Pathophysiology.

Needle or sheath injury leaves a defect in all layers of the arterial wall. Blood escapes and is contained by surrounding tissue and haematoma, forming a cavity in continuity with the artery through a neck.

Pulsatile flow through the neck keeps the sac open. Anticoagulation prevents thrombosis, and the sac expands under arterial pressure, risking skin necrosis, compression of the femoral vein and nerve, retroperitoneal extension and rupture.

Neck length and width decide the success of compression or thrombin injection: a long, narrow neck is favourable, and a short, wide neck predicts failure and risk of thrombin escaping into the artery.

Pain, a tender pulsatile groin mass, a systolic bruit, and a palpable thrill after arterial access, often within hours to days. Expanding haematoma and bruising, leg swelling (venous compression), numbness or weakness (femoral neuropathy), and distal embolisation or ischaemia may be present. Back or flank pain and falling haemoglobin point to retroperitoneal bleeding. Fever, erythema and purulence suggest infection. Rupture causes severe pain and shock.

• Duplex ultrasound is the first test: a hypoechoic cavity with swirling flow ("yin yang" sign), a to-and-fro waveform in the neck, sac size, neck length and width, the relation to the common, superficial and profunda femoral arteries, and the presence of an arteriovenous fistula or haematoma.
• CT angiography when retroperitoneal bleeding, a complex or infected lesion, or vascular disease needs definition, and before surgery or stent graft repair.
• Blood tests: haemoglobin, platelets, coagulation screen, creatinine, group and cross-match when bleeding is suspected. Blood cultures (three sets before antibiotics) and inflammatory markers for suspected infection.
• Ankle brachial index or distal pulses for limb perfusion.

Differential diagnosis.

• Simple groin haematoma, and an arteriovenous fistula at the puncture site.
• True femoral aneurysm, anastomotic pseudoaneurysm after graft surgery.
• Abscess, lymph node, inguinal hernia and lymphocele.
• Retroperitoneal haematoma without pseudoaneurysm.

Emergency (rupture, expanding mass with shock or limb ischaemia, skin necrosis).

• Direct manual pressure proximal to and over the puncture, two large bore intravenous lines, crystalloid or blood by response, group and cross-match, and call the vascular surgeon.
• Reverse anticoagulation when bleeding is life threatening: protamine 1 mg for each 100 units of unfractionated heparin given in the previous 2 to 3 hours (maximum 50 mg, given slowly); for direct oral anticoagulants, use the specific reversal agent or four factor prothrombin complex concentrate 50 units/kg.
• Urgent surgical repair (suture of the artery, patch or interposition graft) or covered stent placement as a bridge. Cefazolin 2 g intravenously within 60 minutes before incision (3 g when weight is over 120 kg).

Non-urgent management by size.

• Under 2 cm (up to 3 cm if asymptomatic, not enlarging, and anticoagulation can be held): observation with duplex at 1 to 2 weeks. About half thrombose spontaneously within 2 to 4 weeks. Continue aspirin 75 to 100 mg daily when indicated, and avoid unnecessary anticoagulation.
• Symptomatic, enlarging, over 2 to 3 cm, or persisting: intervene with one of the following.

Ultrasound directed thrombin injection (first choice for most).

• Under duplex control, inject thrombin 1000 units/mL slowly in 0.1 mL aliquots into the sac, away from the neck, until flow stops (usual total 100 to 1000 units). Success is 90 to 98%, and works despite anticoagulation. Check distal pulses and duplex flow immediately and at 24 hours, and again at 1 to 2 weeks.
• Use human or recombinant thrombin where available, because bovine thrombin can cause antibody formation and, rarely, anaphylaxis. Have resuscitation equipment ready.
• Avoid or use caution with a short (under 1 cm) or wide neck, infection, a very large sac, local skin compromise, or limb ischaemia. Complications are distal embolisation or arterial thrombosis (under 2%), treated with heparin 80 units/kg intravenous bolus then 18 units/kg/h, catheter directed thrombolysis or thrombectomy.

Ultrasound directed compression.

• Apply probe pressure to occlude the neck while preserving arterial flow, for 10 minutes at a time, to a total of 30 to 60 minutes, with analgesia and sedation as needed. Success is about 60 to 90%, lower with anticoagulation, large size and obesity. It is painful and time consuming, so it is used when thrombin is unavailable or unsuitable. Bed rest for 6 hours afterwards, then repeat duplex.

Surgical repair for failed minimally invasive therapy, infection, rupture, skin necrosis, nerve compression, associated arteriovenous fistula that needs repair, a short or wide neck, or a large sac. Technique is direct suture or patch angioplasty of the arterial defect, or interposition graft in a diseased vessel, with evacuation of the haematoma. Heparin 70 to 100 units/kg intravenously before clamping, with protamine 1 mg for each 100 units of heparin given in the previous 2 to 3 hours (maximum 50 mg, given slowly) when reversal is needed.

Covered stent placement for selected high risk patients, preferring the common femoral artery only when there is no overlap of the profunda origin and with awareness of kinking and fracture at the hip. After stenting: aspirin 75 to 100 mg and clopidogrel 75 mg daily for 3 months, then aspirin alone.

Infected pseudoaneurysm. Draw cultures first. Vancomycin 25 mg/kg intravenously as a loading dose, then 15 to 20 mg/kg every 8 to 12 hours (trough 15 to 20 mg/L), with piperacillin and tazobactam 4.5 g intravenously every 6 hours, adjusted to cultures. Excision with debridement and reconstruction using autologous vein or extra-anatomical bypass, and at least 6 weeks of antibiotics after source control. Do not use thrombin or covered stents for active infection, except as a bridge.

Prevention at access. Ultrasound directed puncture of the common femoral artery over the femoral head, micropuncture technique, smallest suitable sheath, correct use of closure devices, and careful manual pressure for 10 to 20 minutes after sheath removal (longer with anticoagulation).

Monitoring. Duplex 24 hours after treatment and at 1 to 2 weeks (a recurrence can appear days later). Haemoglobin and distal pulses daily while in hospital. Review for groin symptoms at 1 month.

Referral and escalation. Refer every pseudoaneurysm for vascular review within 24 hours, and immediately for expansion, rupture, ischaemia, infection or retroperitoneal bleeding.

Special groups.

• Pregnancy: rare; thrombin injection and compression are used, with left lateral tilt and obstetric input.
• People who inject drugs: expect infection, so take cultures and cover for Staphylococcus aureus including MRSA; address drug use and test for HIV, hepatitis B and C.
• Kidney impairment: limit contrast volume; adjust enoxaparin and direct oral anticoagulants by creatinine clearance.
• Older adults: favour minimally invasive therapy.