Peripheral cannulation, whether femoral or axillary, remains the most commonly used method for establishing cardiopulmonary bypass (CPB) during surgery for acute type A aortic dissection (ATAAD) according to databases like STS. Antegrade arterial perfusion through the axillary artery offers advantages over the retrograde perfusion provided by the femoral artery, as it has proven more effective in preventing malperfusion syndrome and embolism, major contributors to the morbidity and mortality of this condition.

The infrequently used central cannulation of the ascending aorta appears to be gaining more followers due to its convenience and potential advantages over peripheral cannulation. These advantages include the simple and efficient establishment of CPB, avoiding a second incision, antegrade perfusion, and true lumen expansion. However, the widespread adoption of this technique is limited by the lack of solid studies on its outcomes, as only a few retrospective studies with small sample sizes have been conducted to date. Additionally, there remains uncertainty about the safety of this technique, without it leading to an increased risk of rupture or worsening of the dissection.

To address these questions, this observational study included all ATAAD repairs performed at a high-volume hospital in Pittsburgh from 2007 to 2021. Patients were stratified according to the type of aortic cannulation used, whether central, subclavian, or femoral. Survival estimates were made using the Kaplan-Meier method, and a multivariable Cox regression analysis was conducted.

The study population consisted of 577 patients who underwent ATAAD repair. Of these, central cannulation was used in 490 patients (84.9%), subclavian cannulation in 54 patients (9.4%), and femoral cannulation in 33 patients (5.7%). The rates of peripheral vascular disease, moderate or greater aortic insufficiency, and cerebral ischemia differed significantly among the groups, but the baseline characteristics were comparable in other respects. The times for CPB, aortic clamping, and circulatory arrest with antegrade or retrograde cerebral perfusion were significantly shorter in the central cannulation group. There were no differences among the groups in terms of the type of surgery performed on the distal aorta, whether hemiarch replacement, complete arch replacement, or elephant trunk procedure with or without freezing. There were also no differences in the type of proximal aorta reconstruction regarding aortic valve replacement, aortic valve resuspension, or David surgery. Only a higher proportion of Bentall procedures was found in the femoral cannulation group (33.3%) compared to 18% and 13% in the direct aortic and axillary cannulation groups, respectively. Operative mortality was lower in the central cannulation group (9.8%), but this did not significantly differ among the groups. Kaplan-Meier survival estimates were similar among the groups. In the multivariable Cox regression, cannulation strategy was not significantly associated with long-term survival.

The authors conclude that ATAAD repair can be safely performed via central aortic cannulation, with outcomes comparable to those achieved using other methods of peripheral cannulation.

COMMENTARY:

The findings of this study are of utmost importance, as they represent a milestone in comparative research on central aortic cannulation in patients with ATAAD. This study, conducted at a single center, has the largest patient cohort to date, with a total of 490 patients, up to five times the sample size of the next most significant study in this field. Among the most prominent messages and conclusions, we can highlight the following points:

In the majority of ATAAD cases, at least 85%, central aortic cannulation could be performed without difficulty. It emphatically confirms the viability, ease, simplicity, and effectiveness of this technique. It provides a detailed and practical description of the surgical technique, resulting from the extensive knowledge and experience of the research team in this field. The times for CPB, ischemia, and cerebral perfusion during circulatory arrest are significantly shorter with central cannulation than with peripheral. Short-term morbidity and mortality are at least comparable, if not lower, than those observed with peripheral cannulation. The comparison between central arterial and peripheral cannulation in ATAAD has been addressed in several retrospective studies, although all of them had small samples, and none had more than 100 patients in the central cannulation group. Most of these studies showed similar morbidity and mortality results, except for one that demonstrated lower short-term mortality with central cannulation, and another that highlighted the benefits of axillary cannulation. The study led by Kreibich et al., published 5 years ago, had the largest sample size to date. This study compared central with peripheral cannulation and obtained results consistent with the work we are analyzing at this moment, which significantly expands the cohort of patients with central aortic cannulation, nearly multiplying it by five.

Unlike most centers, where peripheral cannulation (axillary or femoral) is the preferred technique, at the Heart and Vascular Institute in Pittsburgh, central cannulation is the preferred option whenever feasible. The article provides useful tips for carrying out this technique. Mainly, cannulation was performed in the distal portion of the ascending aorta, with the caution of not performing it extremely distally to ensure sufficient aortic remnant after resection, necessary for subsequent arch reconstruction. The importance of coordination with the anesthesiologist, who by TEE, confirms the correct position of the guide in the true lumen after its insertion using the Seldinger technique, is highlighted. The cannulas used were of the femoral type, with a caliber of 18-20 Fr.

At the Complexo Hospitalario Universitario de A Coruña (CHUAC), we have experienced a change in our cannulation policy for treating ATAAD in recent years. Currently, direct aortic cannulation has become our preferred choice in most cases of ATAAD. The results obtained and our impressions in this regard have been very satisfactory. In relation to the technique, I would like to share some practical tips derived from our experience that can contribute to carrying out this cannulation with greater precision and safety. Firstly, it is crucial to perform a thorough evaluation of the angio-CT of the aorta. This not only allows us to determine the suitability and feasibility of the procedure but also provides us an understanding of the trajectory and location of the true lumen in the vicinity of the intended cannulation area. In most cases, the true lumen is found near the minor curvature of the aortic arch. Although occasionally its diameter may seem small and much smaller compared to the false lumen, it is important to note that the actual size is usually larger, as the angio-CT, being performed in the diastolic phase, always reduces its apparent size. This means that, when performing the cannulation in the distal ascending aorta, near the pulmonary artery, the depth at which we find the true lumen may vary depending on the case, but almost always we will find it there. To facilitate the puncture using the Seldinger technique, described in the article, we also use epiaortic ultrasound. This provides us a clear depth at which the true lumen is located, allowing us to visualize in real-time the puncture and insertion of the guide. Once inside, we advance towards the descending aorta. At this stage, TEE comes into play, confirming precisely that the guide is inside the true lumen. At this point, we proceed to the cannulation with a cannula, in our case of the EOPA type from Medtronic® of 18-20Fr. However, instead of inserting just 2 cm, we advance it 3 to 5 cm and fix it to the skin or cloth to avoid unintentional decannulation during the cooling process in the CPB.

In their article, Yousef et al. describe that the only contraindications for carrying out central aortic cannulation, based on safety issues, were cases of rupture and tear (primary or secondary) in the arch, as well as circumferential dissection of the same. These situations represented only 15% of the dissections intervened. However, in our experience, even in these cases, it would be feasible to perform central cannulation.

Evidently, the main limitation of this study lies in its retrospective and observational design. Moreover, surgeons had the freedom to choose between central and peripheral cannulation, depending on their preferences and the patient’s anatomy. Although confounding factors were controlled through multivariate analysis, patients undergoing peripheral cannulation, whether axillary or femoral, generally represented cohorts with higher surgical risk and underwent more complex procedures. The small sample size of the group of patients cannulated peripherally is a limitation in itself due to its lower statistical power and the impossibility of conducting a propensity analysis. Lastly, the fact that the study was conducted at a single high-volume center, with extensive experience in central cannulation, raises questions about the generalizability of these results to other institutions.

As Henry Ford once said: “if you always do what you’ve always done, you’ll always get what you’ve always got.” Counterintuitively, some surgical techniques in cardiac surgery, such as transcatheter aortic valve replacement through a transcarotid approach, are proving to be equally valid or even superior options to those traditionally considered of choice. Similarly, in the case of ATAAD, central aortic cannulation, at first glance and without knowledge of these studies, might not seem the most logical option due to the risk of a definitive rupture of an already compromised aorta. However, studies like the one conducted by Yousef et al., which demonstrate that central aortic cannulation offers results at least comparable and can be performed safely, support the idea of adopting it as the technique of choice in most cases of ATAAD, or at least considering it as an available option if necessary.

REFERENCE:

Yousef S, Brown JA, Serna-Gallegos D, Navid F, Zhu J, Thoma FW, et al. Central versus peripheral cannulation for acute type A aortic dissection. J Thorac Cardiovasc Surg. 2024 Feb;167(2):588-595. doi: 10.1016/j.jtcvs.2022.04.055.