Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) has become a vital intervention for patients in cardiogenic shock or cardiac arrest who fail to respond to conventional therapies. Traditionally, femoral artery cannulation is the most common approach due to its ease and speed, particularly in emergencies. However, femoral access introduces significant challenges, including limb ischemia, vascular trauma, retrograde flow complications, and the dangerous phenomenon of North–South syndrome, in which poorly oxygenated blood perfuses the upper body while the lower body receives oxygen-rich ECMO blood.
This article, Alternative Arterial Access in Veno-Arterial ECMO: The Role of the Axillary Artery, offers a comprehensive review of the axillary artery as a promising alternative access site. Drawing from over two decades of literature, the authors detail anatomical considerations, surgical and percutaneous techniques, hemodynamic consequences, clinical outcomes, and complication profiles of axillary cannulation.
Anatomical and Technical Considerations
The axillary artery, a continuation of the subclavian artery, is anatomically advantageous for ECMO cannulation. The third segment of the axillary artery is most frequently used, offering a relatively superficial course with reduced risk of displacement and less proximity to major nerve trunks. Right axillary access is preferred due to a more favorable trajectory for cerebral perfusion and fewer surgical risks compared to the left.
Surgically, axillary cannulation often involves a side-graft technique, where an 8–10 mm Dacron graft is sewn end-to-side onto the artery. This preserves antegrade limb flow, minimizes ischemia, and supports reliable ECMO inflow. Alternatively, percutaneous ultrasound-guided cannulation is emerging, using Seldinger’s technique for real-time vessel access. While minimally invasive, percutaneous approaches remain technically demanding and are less established in unstable patients.
Hemodynamic Advantages
Unlike femoral cannulation, which delivers retrograde flow up the descending aorta, axillary cannulation provides antegrade perfusion directly into the aortic arch and supra-aortic vessels. This has multiple benefits:
- Improved cerebral oxygenation: Ensures oxygenated blood supply to the brain and coronary circulation.
- Reduced North–South syndrome: Prevents mixing of desaturated blood ejected from the left ventricle with oxygenated ECMO blood.
- Lower afterload compared to femoral access: Though V-A ECMO inherently increases left ventricular afterload, axillary flow reduces the hemodynamic stress relative to retrograde femoral cannulation.
These physiologic advantages contribute to better myocardial recovery, decreased pulmonary congestion, and more stable cerebral perfusion.
Clinical Evidence and Outcomes
Clinical studies consistently show that axillary cannulation reduces limb ischemia and wound complications compared to femoral access. For instance, Ohira et al. reported significantly fewer vascular complications with axillary access in a cohort of 371 patients, without compromising survival. Similarly, Pisani et al. demonstrated high feasibility with low complication rates in 174 patients, while Radwan et al. observed a one-year survival of over 70% among successfully weaned patients after axillary cannulation.
Hemodynamic studies reveal that femoro-axillary ECMO configurations preserve left ventricular outflow dynamics better than femoro-femoral setups, preventing obstruction from retrograde flows. Simulation models further confirm axillary cannulation delivers adequate cerebral perfusion at lower ECMO flow rates compared to femoral access.
Complications and Limitations
Despite clear advantages, axillary cannulation presents its own risks. Complications include:
- Upper extremity hyperperfusion and edema.
- Bleeding or hematoma formation.
- Brachial plexus injury due to proximity of nerves.
- Rare but catastrophic events such as aortic dissection.
Technical limitations include smaller vessel caliber, restricting flow rates compared to femoral arteries, and the need for surgical decannulation in controlled environments. Furthermore, conflicting reports exist regarding neurologic outcomes, with some studies linking axillary cannulation to higher seizure risk, while others report improved cerebral perfusion.
Indications and Patient Selection
Axillary cannulation is particularly indicated in patients with:
- Severe peripheral arterial disease precluding femoral access.
- Morbid obesity where femoral access is difficult and infection-prone.
- High risk of North–South syndrome.
- Need for preserved cerebral and coronary perfusion.
- Anticipated long-term ECMO support or early mobilization strategies.
Contraindications include local infection, prior vascular interventions, small vessel diameter (<6 mm), and complex aortic arch or subclavian disease. Pre-procedural imaging such as CT angiography and duplex ultrasound is recommended for assessing feasibility and safety.
Future Directions
While evidence supports axillary access as a safe and physiologically favorable alternative, much of the current literature is retrospective, with significant variability in technique. Prospective multicenter studies and standardized protocols are essential to determine the long-term outcomes and refine patient selection. Emerging percutaneous methods hold promise but require further validation.
Conclusion
Axillary artery cannulation for V-A ECMO represents a compelling alternative to femoral access, particularly in high-risk patients. By offering antegrade systemic perfusion, improved cerebral and coronary oxygen delivery, and reduced vascular complications, it enhances physiologic support and long-term management. Nevertheless, technical complexity, risk of limb hyperperfusion, and the need for specialized expertise limit its widespread adoption. Until more robust evidence is available, axillary access should be considered in experienced centers for selected patients where femoral cannulation is suboptimal or contraindicated
