Management of post-catheterisation pseudoaneurysms

Graham John Munneke, Robert Morgan and Anna-Maria Belli
Department of Vascular Radiology, St George’s
Hospital, London, UK
Address for correspondence:
Dr Graham John Munneke, MRCP, FRCR
Department of Vascular Radiology
St George’s Hospital, Blackshaw Road
London SW17 OQT UK
Tel: +44 (0)208 725 3298
Fax: +44 (0)208 725 2936
Email: grahamm@doctors.org.uk


Abstract
Post-catheterisation pseudoaneurysms (PCPA) can develop when there is inadequate haemostasis at an arterial puncture site and occur at a rate of 7.7% following catheterisation. Risk factors for the development of PCPA and subsequent complications are described. Intravascular injection of thrombin has replaced ultrasound-guided compression as treatment for PCPA. Thrombin injection offers advantages including reduced procedure time, no requirement for sedation or local anaesthetic and a high technical success rate. A method is described for the slow injection of thrombin into the periphery of a pseudoaneurysm under continuous ultrasound scanning, which enables resolution with minimal risk of complications. A treatment algorithm for PCPA using thrombin injection is proposed.

Introduction
The exponential rise in the number and complexity of trans-catheter vascular interventional procedures has led to a similar rise in access site complications. A prospective study found the rate of post-catheterisation pseudoaneurysms (PCPA) to be 7.7% [1].

Aetiology
Pseudoaneurysms develop when there is inadequate haemostasis at the arterial puncture site. Blood flows into the perivascular space, forming a pulsatile haematoma contained by surrounding soft tissue, hence the name pseudoaneurysm.

Risk factors for the development of PCPA

  • Interventional procedure or prolonged catheterisation
  • Obesity
  • Anticoagulation or thrombolysis
  • Large sheath size (>7 French)
  • Inadequate compression
  • Faulty puncture technique, e.g. superficial or profunda femoris artery puncture
  • Aberrant anatomy – high branching common femoral artery
  • Calcified artery
  • Hypertension

Figure 1a Figure 1b Figure 1c
Figure 1. (a) Greyscale ultrasound image of the groin at the level of the common femoral artery (CFA). A bi-lobed pseudoaneurysm (PA) is present. The pseudoaneurysm neck is arrowed. (b) Swirling pattern seen on colour Doppler ultrasound. The pseudoaneurysm neck is arrowed. (c) Spectral Doppler trace from the neck of a pseudoaneurysm. Note the characteristic “to and fro” flow pattern.
Diagnosis
PCPA is suspected on clinical grounds when there is a pulsatile mass following recent arterial puncture. The diagnosis is easily confirmed on Doppler ultrasound ( Figure 1).

Complications of PCPA
  • Rupture – risk increases with size
  • Persistent pain
  • Distal embolisation
  • Pressure necrosis of overlying skin
  • Compression of adjacent vascular and neural structures
  • Infection

Figure 2
Figure 2. Suggested treatment algorithm for PCPA.
Treatment Until recently, pseudoaneurysms were treated surgically. In 1991, Fellmeth et al [2] described the technique of ultrasound-guided compression. In this, ultrasound is used to guide compression of the aneurysm neck, thus abolishing flow into the aneurysm leading to thrombosis. In the late 1990s, several papers described the use of percutaneous injection of thrombin to embolise pseudoaneurysms [3-5]. The technique had in fact been reported a decade prior to this by Cope and Zeit [6] but had not gained favour. In recent years, thrombin injection has largely replaced ultrasound-guided compression for the reasons listed in Table 1 [7-9].

Table 1
Table 1. Ultrasound-guided compression vs. thrombin injection for treating pseudoaneurysms

Percutaneous thrombin injection has been used to treat PCPA in other areas such as the brachial and subclavian arteries, in children and in traumatic pseudoaneurysms [10]. Embolisation of pseudoaneurysms with coils or materials such as ethylene vinyl alcohol copolymer (ONYX™) [8,11] has not gained widespread favour as both methods leave a permanent lump in the groin. Others have advocated the use of covered stent grafts to exclude the aneurysms, but these may occlude and make further arterial access at the site difficult [8]. Figure 2 displays a suggested treatment algorithm for PCPA.

Thrombin for PCPA
Figure 3
Figure 3. Ultrasound-guided puncture of pseudoaneurysm.
Thrombin is the active form of prothrombin. Thrombin that inadvertently leaks into the circulation is rapidly diluted and antagonised by the anticoagulant factors thrombomodulin and antithrombin III [12]. After obtaining informed consent, and ensuring there are no contraindications (Table 2), an ultrasound examination is used to define the relationship of pseudoaneurysm, pseudoaneurysm neck and native vessels.

The peripheral pulses are then documented. Under sterile conditions, a 22-gauge spinal needle is inserted with ultrasound guidance into the periphery of the pseudoaneurysm (Figure 3).

The needle tip should be placed as remote from the pseudoaneurysm neck as possible. Human thrombin at a strength of 1000 units/mL should be injected slowly via a 1 mL syringe. The pseudoaneurysm is scanned continuously and injection terminated when colour flow ceases (Figure 4)
Figure 3A Figure 3B Figure 3C
Figure 4. (a) Colour Doppler image from the same patient as Figure 1a. Blood is seen jetting into the pseudoaneurysm (PA) from the common femoral artery (CFA). (b) The locule furthest away from the neck is punctured under ultrasound guidance. Greyscale imaging is used during puncture, as the needle is most conspicuous in this mode. (c) Colour Doppler image showing thrombosis of the most superficial locule. There is still flow within the deeper locule. This was subsequently punctured and embolised.

Figure 5
Figure 5. Ultrasound scan 24 hours following thrombin injection showing echogenic thrombus within the pseudoaneurysm and absence of flow on colour Doppler.
If there is persistent flow after the first dose, a further dose should be prepared and injected. Many pseudoaneurysms will thrombose with as little as 0.2 mL (200 units) of thrombin. Multilocular pseudoaneurysms may require more than one puncture to thrombose all the locules. If the main pseudoaneurysm has thrombosed but there is still flow in the pseudoaneurysm neck, further thrombin should not be given. This risks distal embolisation of thrombin, and the pseudoaneurysm neck has been shown to spontaneously thrombose soon after the body of the pseudoaneurysm [13]. The peripheral pulses are re-examined at the end of the procedure to exclude distal embolisation. Patients should have 4 hours of bed rest and be re-scanned at 24 hours (Figure 5).

Thrombin preparations
The various thrombin preparations available are not currently licensed for intravascular use and so must be used on a named-patient basis.

Figure 6
Figure 6. The Tisseel™ kit (Baxter, Glendale, CA) contains two components. The human thrombin in the black vial on the right is reconstituted with calcium chloride solution. The blue vials on the left contains a tissue adhesive consisting of other clotting factors that are reconstituted with bovine aprotinin solution. This component should not be used as the thrombin solution provides adequate thrombosis and avoids the use of a bovine product.
Bovine-derived thrombin (1000 units/mL; Johnson & Johnson, Middleton, WI) has been associated with documented allergic [14] and anaphylactic reactions [15]. In addition, there is concern that antibodies produced in response to bovine thrombin can cross-react with their human counterparts and produce haemorrhagic complications [16]. For these reasons it is advisable to use human thrombin preparations - for example, Tisseel™ (Baxter, Glendale, CA) (Figure 6). Autologous thrombin derived from the patient's own blood has been successfully used to treat PCPA [17] and avoids the theoretical risk of transmitting disease, but cannot be harvested from patients on anticoagulants.

Complications
Reported complication rates are less than 5% [8] and many series quote a zero complication rate [7,9,13,18-21]. Complications broadly divide into immune responses and thrombotic events. The use of human thrombin avoids the risk of the former. Native vessel thrombosis has been described. The likely explanation is the injection of relatively large volumes of thrombin into small pseudoaneurysms [22,23]. Injecting 1000 units/mL strength thrombin slowly, via a 1 mL syringe, and ceasing injection immediately when thrombosis occurs minimises this risk. Distal embolisation may occur when the pseudoaneurysm neck is wide. Lennox et al [24]. described thrombosis of the brachial artery following treatment of a pseudoaneurysm whose neck was the same width as the native artery. Inflation of a balloon catheter across the pseudoaneurysm neck during embolisation may prevent this [5]. When it does occur, native vessel thrombosis may resolve spontaneously [12,22] or may require intervention [25].

Acknowledgement
The authors thank Dr Arum Parthipun for supplying artwork for the article.

Key Learning
  • Pseudoaneurysm is an access-site complication following catheterisation
  • Diagnosis can be confirmed by Doppler ultrasound scanning
  • Thrombin injection has replaced ultrasound-guided compression as treatment for post-catheterisation pseudoaneurysm
  • Use of human thrombin preparations avoids allergic and anaphylactic reactions; these preparations must currently be used for intravascular use on a named-patient basis
  • During continuous ultrasound scanning, thrombin is injected slowly into the periphery of the pseudoaneurysm, and injection is terminated when colour flow ceases
  • Complication rates following treatment are 0–5%

References
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December 2004, 1098/OS