Overview
Definition:
Axillary-axillary bypass is a surgical procedure involving the creation of a vascular conduit between the two axillary arteries
This technique is primarily utilized in thoracic surgery to revascularize the head and neck vessels when direct cannulation or repair of the proximal great vessels (subclavian, innominate, or common carotid arteries) is challenging or impossible.
Epidemiology:
The incidence of conditions requiring axillary-axillary bypass is relatively low, typically associated with complex aortic arch pathologies, traumatic injuries to the great vessels, or as part of complex reconstructive procedures like those for thoracoabdominal aneurysms or congenital anomalies
Specific epidemiological data is scarce due to its specialized nature.
Clinical Significance:
This bypass technique is crucial for maintaining adequate cerebral and upper extremity perfusion during extended aortic arch procedures or when the origin of the brachiocephalic trunk, left common carotid artery, or left subclavian artery is compromised
It provides a vital source of blood flow to the brain and upper limbs, preventing ischemic complications
Proficiency in this technique is essential for cardiothoracic and vascular surgeons managing complex pathologies involving the aortic arch and its branches.
Indications
Absolute Indications:
Dissection or occlusion of the innominate artery and left common carotid artery
Severe atherosclerotic disease involving multiple origins of the great vessels
Traumatic transection or injury to the innominate or subclavian arteries requiring proximal control
As a component of extended aortic arch or ascending aorta repair where direct cannulation is unsafe.
Relative Indications:
Need for antegrade cerebral perfusion during aortic arch surgery when standard methods are not feasible
Previous interventions on the great vessels that compromise access
Complex congenital heart disease with aberrant great vessel anatomy.
Contraindications:
Severe ipsilateral axillary artery occlusive disease
Significant aortoiliac occlusive disease if femoral access is also required
Patient with extremely poor physiological reserve where prolonged cardiopulmonary bypass is not tolerated
Active infection at the axillary artery or groin sites.
Preoperative Preparation
Patient Assessment:
Thorough cardiovascular assessment, including evaluation of coronary artery disease, valvular heart disease, and peripheral vascular disease
Detailed neurological assessment to establish a baseline
Evaluation of pulmonary function and renal function.
Imaging Studies:
Computed tomography angiography (CTA) of the chest, abdomen, and pelvis to delineate the extent of aortic disease and assess the anatomy of the great vessels, including the axillary arteries
Transesophageal echocardiography (TEE) for intraoperative assessment of cardiac function and aortic pathology
Magnetic resonance angiography (MRA) may be used in select cases.
Blood Product Preparation:
Availability of adequate cross-matched blood products is essential, given the potential for significant blood loss during aortic and vascular procedures
Typically, 4-6 units of packed red blood cells, fresh frozen plasma, and platelets are prepared.
Anticoagulation Strategy:
Heparinization will be required during bypass
Preoperative medications should be reviewed, and anticoagulants or antiplatelet agents managed according to established protocols.
Procedure Steps
Exposure And Access:
Bilateral axillary artery exposure is performed, usually through supraclavicular and deltopectoral incisions
The axillary arteries are carefully dissected free from surrounding tissues, ensuring preservation of the brachial plexus and surrounding nerves
Careful attention is paid to control of the thoracoacromial and lateral thoracic arteries to minimize bleeding.
Graft Selection And Preparation:
A synthetic graft (e.g., Dacron or PTFE) is typically used
The graft length is determined by the distance between the selected cannulation sites on both axillary arteries
The graft is pre-clotted if a woven Dacron graft is used.
Anastomosis Technique:
Continuous or interrupted sutures (e.g., polypropylene) are used for end-to-side anastomoses
The proximal anastomosis is usually performed on the less diseased axillary artery
The distal anastomosis is performed on the contralateral axillary artery
Careful attention is paid to achieving a leak-free anastomosis and avoiding kinking or tension on the graft.
Cannulation And Flow:
Once the anastomoses are complete, the graft is flushed and the distal anastomosis is partially occluded
Heparin is administered systemically
The graft is then fully connected to the contralateral axillary artery, and flow is restored
Hemostasis is meticulously achieved at all suture lines
If used for cerebral perfusion, the graft may be selectively cannulated to allow antegrade flow.
Graft Traversal And Closure:
The graft is tunneled in the subcutaneous or pre-pectoral plane
Meticulous hemostasis is achieved throughout the dissection
Drains are typically placed in the axillary wounds
The incisions are closed in layers.
Postoperative Care
Hemodynamic Monitoring:
Close monitoring of blood pressure, heart rate, and oxygen saturation is critical
Vasopressors or inotropes may be required to maintain adequate perfusion
Central venous pressure monitoring is often employed.
Neurological Monitoring:
Frequent neurological assessments to detect any signs of cerebral ischemia, such as altered mental status, focal neurological deficits, or seizures
Transcranial Doppler or somatosensory evoked potentials may be used for continuous monitoring of cerebral blood flow.
Anticoagulation Management:
Postoperative anticoagulation is typically managed with unfractionated heparin or low-molecular-weight heparin (LMWH), with careful monitoring of activated partial thromboplastin time (aPTT) or anti-Factor Xa levels
Duration and intensity of anticoagulation depend on the overall clinical context and risk of thrombosis.
Wound Care And Drainage:
Routine wound care to prevent infection
Drains are monitored for output and removed when appropriate
Edema in the upper extremities should be monitored.
Complications
Early Complications:
Graft thrombosis, leading to limb or cerebral ischemia
Hemorrhage from anastomotic sites or surrounding tissues
Neurological deficits (stroke, transient ischemic attack)
Lymphocele or seroma formation
Wound infection
Air embolism.
Late Complications:
Graft pseudoaneurysm formation
Graft occlusion
Distal embolization
Chronic limb ischemia
Graft infection
Stenosis at the anastomotic sites.
Prevention Strategies:
Meticulous surgical technique to ensure adequate anastomic flow and hemostasis
Careful graft selection and handling
Adequate heparinization
Judicious use of intraoperative neuromonitoring
Prophylactic antibiotics
Close postoperative surveillance for neurological and vascular compromise.
Prognosis
Factors Affecting Prognosis:
The success of axillary-axillary bypass is closely linked to the patient's underlying pathology and overall physiological status
Factors influencing outcome include the indication for the bypass (e.g., elective repair vs
emergent trauma), the presence of comorbidities, the technical success of the anastomosis, and the adequacy of postoperative perfusion.
Outcomes:
When performed electively in carefully selected patients with appropriate technique, axillary-axillary bypass can provide durable revascularization, preventing catastrophic ischemic events
However, the morbidity and mortality rates are related to the complexity of the underlying aortic or great vessel disease
Long-term patency rates for synthetic grafts in this setting vary but are generally acceptable when used for limb salvage or cerebral protection.
Follow Up:
Long-term follow-up with regular clinical examinations and vascular imaging (e.g., duplex ultrasound, CTA) is recommended to monitor graft patency and detect any late complications such as stenosis or pseudoaneurysm formation
Patients are also monitored for signs of distal embolization or recurrent ischemic events.
Key Points
Exam Focus:
Understand the indications for axillary-axillary bypass, particularly in the context of aortic arch surgery
Recognize the key steps of the procedure, including exposure, graft choice, and anastomosis technique
Be aware of the critical postoperative monitoring for neurological and vascular complications.
Clinical Pearls:
Ensure meticulous dissection of the axillary arteries to avoid injury to adjacent nerves and vessels
Use appropriately sized grafts to prevent anastomotic tension or stenosis
Always ensure adequate heparinization before initiating bypass
Perform thorough intraoperative imaging to confirm graft patency and exclude complications before closure.
Common Mistakes:
Inadequate proximal control of the axillary artery
Suboptimal anastomotic technique leading to leaks or stenosis
Insufficient heparinization, increasing the risk of graft thrombosis
Failure to adequately monitor cerebral perfusion during the procedure
Overlooking or underestimating the risk of distal embolization.