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Troncone et al. Vessel Plus 2023;7:14 https://dx.doi.org/10.20517/2574-1209.2023.08 Page 7 of 15

percutaneous femoral venous cannula; in either situation, they ensured the tip was pointing towards the
[34]
superior vena cava . Using a connecting bridge between the arterial and venous cannulas, once DHCA was
achieved and the aorta transected, they initiated flow from the arterial to venous cannula via the connecting
bridge at a rate of 700-1,000 mL/min targeting a central venous pressure of 15 to 20 mmHg. Returned blood
from the brachiocephalic arch vessels was collected via cardiotomy suctions to maintain retrograde flows
and reservoir volume. They noted a 2.8% stroke rate with retrograde perfusion coupled with DHCA
compared to a 12% stroke rate in the DHCA only cohort, despite the retrograde group having longer DHCA
times. They point towards the ability of retrograde perfusion in flushing out air and debris from the cerebral
vasculature as the likely mechanism of lower stroke rate. There have been other variations of retrograde
flow in the repair of DTA/TAAAs in the literature, including distal aortic clamping and low-flow femoral
arterial perfusion with steep Trendelenburg, allowing passive venous return to the right heart to fill the
cerebral venous system and eventually drain out through the arch vessels. Nevertheless, the utilization of
retrograde cerebral perfusion in the repair of DTA/TAAAs remains an attractive option for the potential
reduction of embolic neurologic complications via the flushing of air and debris. In fact, one may combine
these techniques by providing antegrade cerebral perfusion via selective carotid catheters during the
proximal anastomotic creation, which can be removed, and retrograde cerebral perfusion instituted briefly
to allow flushing of debris just prior to completion of the anastomosis, thereby combining the benefits of
both methods, albeit at the expense of increased technical complexity. All these techniques will require
further study prior to any recommendations being made on any of their superiority over others.

While there are numerous techniques described to improve the safety of DHCA in the repair of DTAs/
TAAAs, it cannot go unstated that the development of newer hybrid surgical grafts will also improve the
outcomes of these complex repairs. Many of the described adjunctive perfusion strategies aimed at reducing
the risk of complications associated with DHCA suffer from both anatomic constraints and overall
unfamiliarity of their execution in the context of a left thoracotomy incision. This has driven the
development of newer hybrid grafts, such as the Terumo Thoraflex Plexus and Ante-Flo grafts, permitting
intervention of DTAs and proximal thoracic aneurysms from a midline sternotomy, simplifying the surgical
exposure as well as permitting the surgeon access to more familiar and facile techniques at cerebral
[29]
protection . Furthermore, these grafts can create a stable proximal landing zone for subsequent
endovascular intervention of the thoracoabdominal aorta or provide a first stage repair that subsequently
facilitates the second stage open thoracoabdominal repair. How these grafts are utilized and consequently
compare in terms of post-operative outcomes and neurologic complications remains to be seen in reference
to standard left thoracotomy approaches with various protection strategies.

DHCA provides acceptable cerebral protection. There is evidence in the literature to support aortic arch
surgery for time periods of up to 40 min [35,36] . Other adjuncts which have been used to provide cerebral
protection, either supplementally to deep hypothermia or with more milder temperatures, include
antegrade and/or retrograde cerebral perfusion. Options for antegrade cerebral perfusion include right
axillary cannulation, in addition to femoral cannulation for DTA and TAAA repair . The benefits of using
[37]
axillary artery perfusion in addition to femoral arterial perfusion are two-fold. Firstly, during cooling and
fibrillation, cerebral blood flow is provided either partially or completely by retrograde femoral perfusion,
which may pose an increased thromboembolic stroke risk, especially given the atheromatous nature of
DTAs and TAAAs . This risk is also manifested after completion of the proximal anastomosis and
[38]
connection of the graft perfusion limb, as well as during re-warming and weaning off CPB, as until the heart
resumes complete hemodynamic function with no venous drainage, a certain proportion of blood flow will
remain retrograde. Secondly, during the proximal open anastomosis for DTAs/TAAAs during period of
circulatory arrest, patients are placed in steep Trendelenburg position and various de-airing maneuvers are