Continuing Education Activity

Pseudoaneurysms are false aneurysms that occur at the site of arterial injury. They are unlike true aneurysms as a layer of the arterial wall does not contain them. Prompt recognition and treatment are required. This activity will cover the epidemiology, pathophysiology, evaluation, and treatment of the most commonly encountered types of pseudoaneurysms, including femoral, visceral, and aortic pseudoaneurysms. These are separate disease entities which occur in a myriad of situations and require specific workup and treatment. This activity reviews the evaluation and treatment of pseudoaneurysms and highlights the role of the interprofessional team in evaluating and treating patients with this condition.

Objectives:

• Review the risk factors for developing pseudoaneurysms, specifically femoral, visceral, and aortic pseudoaneurysms.
• Describe the evaluation of pseudoaneurysms.
• Summarize the treatment and management options available for pseudoaneurysms.
• Outline interprofessional team strategies for improving care coordination and communication and improve outcomes with regard to pseudoaneurysms.

Introduction

An arterial pseudoaneurysm, AKA false aneurysm, is caused by damage to the arterial wall, resulting in locally contained hematoma with turbulent blood flow and a neck that typically does not close spontaneously once past a certain size. Unlike a true aneurysm, a pseudoaneurysm does not contain any layer of the vessel wall.  Instead, there is blood containment by a wall developed with the products of the clotting cascade.  Eventually, a wall forms from fibrin/platelet crosslinks that is ultimately weaker than those of a true aneurysm. The most common clinical presentation of a pseudoaneurysm is a femoral pseudoaneurysm following access for endovascular procedures. Other less common presentations include visceral pseudoaneurysms and aortic pseudoaneurysms.  This article will focus on these three entities.

Etiology

The most common cause of femoral pseudoaneurysm is iatrogenic. 

Iatrogenic causes include:

• Arterial access for endovascular procedures (<1% incidence)
• Anastomotic failure

Non-iatrogenic causes include:

• Trauma
• Infection
• Pancreatitis with pseudocyst/pancreatic fistula 

Visceral artery pseudoaneurysms can occur with catheter-based interventions and are also associated with pancreatitis and pseudocysts. 

Aortic pseudoaneurysms are often the result of blunt or penetrating trauma, infection, atherosclerotic penetrating/degenerative lesions, and at anastomotic sites following vascular bypass or repair.

Epidemiology

Femoral pseudoaneurysms typically result from access for catheter-based interventions and carry an incidence of 0.6 to 4.8%.[1] With the increasing use of ultrasound for access, some society guidelines quote that the acceptable rate of pseudoaneurysm after percutaneous access should be less than 0.2%.[2]

Visceral artery pseudoaneurysms are associated with chronic pancreatitis.[3]  Splenic artery pseudoaneurysms were most common but least likely to rupture. 

Aortic pseudoaneurysms are often the result of trauma or penetrating aortic lesions. Of those with aortic injuries secondary to blunt trauma, an estimated 85% die before reaching medical care.  90% of blunt thoracic aortic injuries occur just distal to the aortic isthmus and are a result of deceleration injury from tethering to the ligamentum arteriosum [4]. Aortic pseudoaneurysm is considered a grade III aortic injury, now most commonly treated with  thoracic endovascular aortic repair (TEVAR) rather than open surgery [5]. Rarely, the cause of thoracic aortic pseudoaneurysms is advanced tuberculosis.[6] Research quotes pseudoaneurysms following aortobifemoral bypass at 3.8% in one 11-year series.[7]

Pathophysiology

Femoral pseudoaneurysms after percutaneous access can occur due to[8]:

• Failures of closure devices
• Laceration of the artery or branches of the common femoral artery by access needle
• Inadequate pressure or length of time holding pressure post-procedure
• Inadvertent access and/or dilation of the artery during venous procedures

Femoral graft anastomosis can also break down over time due to suture failure, or likely more commonly due to infection of the graft material.

Visceral pseudoaneurysms are very rare and are related to iatrogenic injury from surgery or endovascular procedures, or pancreatitis, which typically presents as a splenic artery pseudoaneurysm, which is due to the digestive action of pancreatic enzymes on the artery.[9] Unlike true aneurysms, visceral pseudoaneurysms appear in myriad locations.  One study found the distribution of visceral artery pseudoaneurysms to be: celiac axis and branches 39%, hepatic 39%, splenic 18%, and SMA 4%.[10]

Aortic pseudoaneurysms due to blunt trauma are theorized to be caused in large part by deceleration forces between the relatively free aortic arch against the relatively fixed descending aorta, especially at the point where the ligamentum arteriosum anchors the aorta to the pulmonary artery. This fact, in combination with the pinching effect between the sternum and the spine, and the water hammer effect caused by squeeze forces can cause partial to total rupture of the thoracic aorta.[4]

History and Physical

Typically, an iatrogenic femoral pseudoaneurysm presents as a painful, pulsatile mass.  The mass will frequently exhibit a bruit on auscultation.  If there is an arterio-venous fistula, the bruit may demonstrate a to-and-fro quality.  Enlarging pseudoaneurysms may exhibit pressure on the skin with pain with ultimately skin ischemia, necrosis, and hemorrhage.  Thrombus that forms within the sac may embolize distally.

Most visceral artery pseudoaneurysms (91%) present with symptoms of rupture.[11] Historically this was termed abdominal apoplexy.

Aortic and femoral pseudoaneurysms are rarely spontaneous.  Mycotic pseudoaneurysms are typically the result of repeated IV drug use.[12] Repair of these can be challenging, given the paucity of usable veins for conduit in drug abusers as well as grossly infected fields.

Evaluation

A full history and physical exam are necessary.  Most cases of femoral pseudoaneurysm are iatrogenic.  Physical exam findings of a pulsatile mass in the groin carries a 92% sensitivity and 93% specificity in the diagnosis of a femoral pseudoaneurysm.[13] Duplex ultrasonography remains the gold standard for diagnosis, as it can also evaluate for size, anatomy, and origin of pseudoaneurysms.  A CTA helps define the relation to surrounding structures, though this exam is unnecessary in straight forward cases. Understanding the characteristics of the pseudoaneurysm helps guide treatment

Visceral pseudoaneurysms can present with signs of bleeding and abdominal pain.  CT angiography or conventional angiography can help characterize the lesion. 

The diagnosis of aortic pseudoaneurysms is most commonly via CTA or conventional arteriography. They may have a history of previous open repair of dissection or aneurysm, blunt or penetrating trauma, infection, or genetic disorders which predispose to aneurysmal degeneration of the aorta such as Marfan syndrome or Ehlers-Danlos syndrome.

Treatment / Management

Femoral artery pseudoaneurysms caused by endovascular access used to be treated exclusively by surgical means, but in the last few decades, the paradigm has shifted to less invasive measures. Options for management include observation, ultrasound-guided compression, ultrasound-guided thrombin injection, and surgical repair — the characteristics of the false aneurysm guide treatment choice.

Femoral artery aneurysms less than 2 to 3 cm in diameter may undergo spontaneous thrombosis and regression with observation.  Those that are larger rarely spontaneously thrombose, though this is not an absolute rule.[14]

Ultrasound-guided thrombin injection is a well-established, minimally invasive method for treating pseudoaneurysms that are accessible. Several studies have reported a very high success rate (97% to 100%) for femoral pseudoaneurysms with a single treatment, even while patients are on anticoagulants and/or antiplatelet agents.[15] Risks of the procedure include embolization and PE, with a shorter aneurysm neck length correlating to a higher risk of embolic complication, with those with a less than 2 mm neck being at the highest risk. Overall, complications are very rare.  Ultrasound-guided thrombin injection is not recommended for pseudoaneurysms under 1 cm due to the theoretical risk of arterial embolization, though these can safely undergo an attempt at ultrasound-guided compression.[2]

Surgical management of femoral pseudoaneurysm is reserved for those who fail at least one unsuccessful duplex-guided compression or thrombin injection,[1] or for those with anastomotic disruptions. If surgical repair is required, blood should be typed and crossed, and available as inadvertent entry into the pseudoaneurysm before achieving proximal and distal control can result in massive bleeding.

Visceral artery pseudoaneurysms are typically treated by endovascular means first, with surgery reserved for failure; this is highly effective, with one study reporting a 98% success rate in control of pseudoaneurysms and ruptured true aneurysms.[11] Techniques include coiling, injections of procoagulant materials, and covered stent deployment to seal the origin of the pseudoaneurysm.

Aortic pseudoaneurysms are now preferably treated with thoracic endovascular aortic repair (TEVAR) or endovascular aneurysm repair (EVAR).[16] Even in cases of mycotic pseudoaneurysm and tuberculous pseudoaneurysm of the aorta, prosthetic stent grafts can be lifesaving and avoid the need for a large open operation in already debilitated patients.[6]

Differential Diagnosis

Differential diagnosis of a femoral pseudoaneurysm includes:

• Hematoma
• Seroma
• Infection/abscess

Prognosis

Conservative management of femoral pseudoaneurysms has higher rates of failure in the setting of dual antiplatelet therapy, but not for those receiving thrombin injection.[1] Ultrasound-guided thrombin injection for femoral pseudoaneurysms caused by vascular access has a high success rate (up to 97% to 100%), even in those taking anticoagulants or antiplatelet agents.  Those that fail can undergo a second attempt, and very few should require surgical correction.[2]

Though not studied well, endovascular repair of visceral pseudoaneurysm carries a high rate of technical success in small series.  Open repair/ligation is considered more durable, however, and may be a better option for younger patients.[3]

Traumatic aortic pseudoaneurysms treated via TEVAR have an excellent technical success rate (100%) with a low rate of device-related complications (2.4%) and conversion to open (2.4%).  Coverage of the left subclavian artery resulted in a 6% rate of delayed revascularization.[17]

Complications

Femoral pseudoaneurysms can rupture into the retroperitoneal space, causing significant bleeding that may not be immediately obvious, which can lead to death.

Complications of ultrasound-guided thrombin injection include distal embolization in up to 2% of patients, though few require any intervention.[18]

Complications of endovascular repair of visceral and aortic pseudoaneurysms are primarily those related to endovascular devices in general and will not be discussed in depth here.

Postoperative and Rehabilitation Care

Open repair of femoral pseudoaneurysms requires no special post-op care above normal care of vascular patients, and the need for rehabilitation is largely predicated on the patient’s overall condition prior to intervention.

Endovascular repair of pseudoaneurysms is generally well-tolerated, and the patient should remain flat for 2 to 4 hours post-procedure with monitoring for the development of subsequent access site pseudoaneurysm.  Repairs that involve the deployment of stent/graft devices will require long term follow-up with a vascular surgeon for surveillance imaging.

Consultations

A vascular surgeon consultation is necessary for all pseudoaneurysms.  A vascular surgeon or interventional radiologist can perform ultrasound-guided compression and thrombin injection, but only a vascular surgeon can treat femoral artery pseudoaneurysms that require surgery.

Deterrence and Patient Education

There are no specific recommendations for deterrence for pseudoaneurysms.  The patient should be made aware of the signs and symptoms of recurrence.

Pearls and Other Issues

Femoral pseudoaneurysm after vascular access is a common problem and are addressable with via less invasive means than open surgery.  Pseudoaneurysms that occur at vascular anastomosis mandate open repair and revision.  Visceral pseudoaneurysms are uncommon, and diagnosis of these is often during an investigation for vague symptoms of abdominal pain, or with CTA imaging with signs of bleeding.  Aortic pseudoaneurysms are rarely spontaneous and result either from infection or trauma.

Enhancing Healthcare Team Outcomes

Management of pseudoaneurysms requires an interprofessional team approach, including physicians, specialists, and specialty-trained nurses all collaborating across disciplines to achieve optimal patient results.

Management of pseudoaneurysm depends on its etiology and location.  Nurses and physicians should routinely palpate the groin area after patients undergo cardiac catheterization, as pseudoaneurysms are not uncommon. A femoral pseudoaneurysm can be treated by the vascular surgeon or by interventional radiology with thrombin injection depending on local practice patterns.  Endovascular repair of visceral artery pseudoaneurysms may be performed by a vascular surgeon or interventional radiologist as well.  Aortic pseudoaneurysms are typically the domain of the vascular surgeon as there is a possible need for open repair and subsequent follow-up. Only the vascular surgeon can perform open repairs of all types of pseudoaneurysms. [Level V]