Cerebral protection during aortic arch surgery requiring open repair remains crucial for favorable clinical outcomes. Right axillary artery cannulation has been the method of choice for many surgeons to achieve ACP during hypothermic circulatory arrest (HCA) in such procedures; however, consensus on the optimal strategy has yet to be reached.
The aim of this study was to compare the safety and efficacy of innominate trunk cannulation versus axillary artery for providing antegrade cerebral protection during elective proximal aortic arch surgery.
The ACE CardioLink-3 study (The Aortic Surgery Cerebral Protection Evaluation CardioLink-3 trial) is a randomized, multicenter clinical trial that includes patients undergoing elective ascending aorta and proximal aortic arch surgery requiring open distal anastomosis for hemiarch replacement. A total of 111 patients were assigned to either right axillary artery or innominate artery cannulation for ACP infusion during the moderate HCA period (nasopharyngeal temperature 25.7°C). The primary safety outcome was neuroprotection, with postoperative severe ischemic lesions on diffusion magnetic resonance imaging (MRI) occurring in 38.8% of patients in the axillary group versus 34% in the innominate trunk group (p for noninferiority = 0.0009). The primary efficacy outcome was total operative time, with no significant difference observed between both arms. Other secondary outcomes, including 30-day mortality (3.9% in the axillary artery group versus 3.7% in the innominate artery group), stroke/transient ischemic attack (7.1% vs. 3.6%), radiographic or analytical markers, and neurocognitive evaluations between the two different ACP cannulation methods, were similar across both groups.
It was concluded that ACP with direct innominate trunk cannulation is safe and provides neuroprotection similar to axillary cannulation during aortic surgery, though the burden of new neurological lesions (as evaluated by diffusion MRI) is high in both groups.
COMMENTARY
The ACE CardioLink-3 trial is the first rigorously conducted randomized study to provide evidence of the non-inferiority of direct innominate trunk cannulation versus right axillary cannulation for ACP in hemiarch aortic surgery.
The efficacy of cerebral protection measures during aortic arch surgery is the most decisive factor in favorable postoperative neurological outcomes. The results of deep hypothermic circulatory arrest (DHCA) served as a reference for years. However, the limited duration of “safe” cold ischemia without neurological sequelae, along with the deleterious systemic effects of deep hypothermia, prompted surgeons to experiment with circulatory arrest at milder hypothermic levels combined with ACP through the supraaortic trunks or retrograde cerebral perfusion via the superior vena cava. Despite numerous existing studies, most of which are retrospective, it remains unclear which cerebral perfusion method (antegrade or retrograde) is optimal for effective brain protection.
Initially, ACP was directly and simultaneously employed through the ostia of the innominate and left carotid arteries with the aortic arch open during DHCA. One of the major drawbacks of this strategy is the discomfort caused by the perfusion cannulas interfering within a confined surgical field. Consequently, selective ACP through right axillary artery cannulation became prevalent, providing cerebral perfusion via the right carotid artery with excellent clinical results due to the high percentage of patients with an intact circle of Willis. However, axillary artery access requires an additional incision distinct from the sternotomy, partial dissection of the pectoralis major and minor muscles, careful isolation of the brachial plexus, and manipulation of the axillary artery (which has notably fragile walls). This is where direct innominate artery cannulation offers a more robust alternative, as it allows access through the same sternotomy incision (possibly extending it slightly cranially) and a simpler dissection process compared to the axillary approach.
Several studies and a meta-analysis have compared axillary versus innominate artery cannulation results, generally finding no significant differences between the two techniques except for a shorter operative time favoring the innominate approach. This randomized study thus holds significant relevance in providing scientific evidence to support what has been previously suspected.
On the other hand, some surgeons argue that direct innominate artery cannulation, being more proximal than the axillary, could pose a higher risk of embolization through the right common carotid and vertebral arteries. Depending on the surgeon’s preferences, some may contend that there is no justification for a secondary cannulation site when perfusion can be achieved directly through the ostium of the innominate artery (when the arch is open and exposed). Axillary cannulation should remain the preferred choice for total arch surgery, mainly because it leaves the innominate artery free for anastomosis with the branch of a four-branched Dacron graft, and the axillary cannula can be used to resume CPB during the rewarming phase. Axillary cannulation should also be the preferred method for acute type A dissections to avoid cannulating a frequently dissected and friable innominate artery, as recommended by the 2014 European Society of Cardiology guidelines on aortopathies.
In contemporary aortic arch surgery, stroke incidence in elective cases is around 5%, while in emergency contexts, it is approximately 12%. This study, with an average stroke incidence of 5.4%, aligns with previously published data. One limitation of this work was that the neurological damage classification was not performed by a neurologist but by clinical follow-up carried out by the cardiac surgeon, potentially underestimating the incidence of neurological events. On the other hand, a high incidence of new severe silent ischemic lesions was detected via MRI in both groups. It is known that new MRI-detected lesions may often not result in clinically significant neurological deficits in the immediate postoperative period. Still, studies with long-term cognitive assessments are required to understand their true influence on brain function. In fact, studies already exist correlating total infarct volume on MRI with specific levels of cognitive impairment in patients undergoing aortic valve replacement.
To date, the optimal cerebral protection strategy for hemiarch replacement remains undetermined. The next step would involve randomized, prospective studies of cerebral protection strategies that, like this study, incorporate thorough and rigorous neurological evaluation.
REFERENCE
Peterson MD, Garg V, Mazer CD, Chu MWA, Bozinovski J, Dagenais F, et al.; ACE CardioLink-3 Trial Working Group. A randomized trial comparing axillary versus innominate artery cannulation for aortic arch surgery. J Thorac Cardiovasc Surg. 2022 Nov;164(5):1426-1438.e2. doi: 10.1016/j.jtcvs.2020.10.152.
