Pseudoaneurysms are a well-known iatrogenic complication of arterial catheterization (Esposito et al. 2006). The pathogenesis originates from inadequate thrombus formation after the catheter or sheath is removed, thus causing a hematoma between the tunica media and tunica adventitia which communicates with the arterial lumen. It is estimated that pseudoaneurysms occur in .2% to 3% of femoral artery catheterizations (Stone et al. 2014). The incidence is much more rare for radial artery catheterization and is estimated at 0.009% (Tatli et al. 2015). The prevalence of radial artery pseudoaneurysm (RAP) is likely to increase in the future as radial access continues to grow in popularity.
The diagnosis of RAP is usually based on a high degree of clinical suspicion and often followed by a doppler ultrasound. Several other imaging modalities can also be used, though angiography remains the gold standard for diagnosis (Mohan et al. 2017).
The potential risks associated with RAP can be significant due to the artery’s proximity to the palmar arch as well as its superficial location within a highly mobile region of the wrist. These risks include distal thromboembolism, digital ischemia, hemarthrosis, parasthesias, rupture, skin ulceration, and secondary infection thus prompting timely intervention (Luzzani et al. 2006; Gabriel et al. 2008). Though no report exist to date, these risks may be higher in cases such as the one described in which the radial artery pseudoaneurysm is located at the anatomical snuffbox.
Several treatment options exist in managing RAP including compression management, ultrasound-guided thrombin injection, and surgical excision with or without radial artery ligation (Nassiri et al. 2016).
While it is the least invasive option, ultrasound-guided compression therapy has a high failure rate and usually requires for the pseudoaneurysm to be located superficially within muscle compartments. (Mohan et al. 2017; Eisenberg et al. 1999). This method is even less successful in patient on anticoagulation (Chandradev and Ateesh 2014).
Similarly, percutaneous thrombin injection can be severely limited by pseudoaneurysm characteristics, namely pseudoaneurysm base morphology and neck length In cases in which the pseudoaneurysm has a broad base and a short neck, there is a high risk of distal digital ischemia from non-target embolization. Thus, assessing a patient’s candidacy for percutaneous thrombin injection requires careful evaluation and scrutiny of the pseudoaneurysm morphology on duplex ultrasonography (Nassiri et al. 2016). Finally, surgery is the most invasive option and may not be an option for patients with multiple comorbidities such as the one described.
In the case described, the embolic agent of choice was ONYX™ liquid embolic system (Medtronic, Irvine, CA) (Ling et al. 2006). To our knowledge, no cases of Onyx™ injection for the treatment of radial artery pseudoaneurysms have been published. Onyx™ is becoming more widespread among interventional radiologists in the treatment of peripheral lesions. It has been used for several years in the treatment of arteriovenous malformations (AVMs) and more recently for filling endoleaks and in peripheral AVMs (Kolber et al. 2015; Guimaraes and Wooster 2011; Urbano et al. 2014; Numan et al. 2004; Abularrage et al. 2011). The material is comprised of EVOH (ethylene vinyl alcohol) copolymer dissolved in DMSO (dimethyl sulfoxide), and suspended micronized tantalum powder to provide contrast for visualization under fluoroscopy. It is available in two formulations: Onyx®-18 (6% EVOH), which was used in the case described, and Onyx®-34 (8% EVOH).
Several characteristics of Onyx allow it to achieve controlled, deliberate, and predictable thrombosis. Onyx has a high viscosity and long polymerization time which allows for slow administration. Unlike glue, Onyx only precipitates in the absence of DMSO. Therefore, preloading microcatheters with DMSO prevents cementing of the catheter tip. This allows the operator to pause and resume injection while leaving the catheter in place. Once it comes in contact with blood, Onyx forms a soft spongy polymer cast. This process begins at the surface while the core remains liquid. This quality of the material creates a smooth flow pattern without any fragmentation during injection and reduces the risk of non-target embolization (Weber et al. 2007).
