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Calafiore et al. Vessel Plus 2023;7:18 https://dx.doi.org/10.20517/2574-1209.2023.42 Page 11 of 21

quantify, is that CP gradually declines with time and not uniformly within the brain, making certain regions
[76]
more susceptible to ischemia .
Results of ACP with a variety of CA temperatures have been widely explored. The ARCH database was used
by Keeling et al. to report 3,265 patients undergoing total arch replacement (55% electively) with ACP and
DHCA or MHCA . Results were similar in propensity-matched patients (669 in each group), with a NDs
[77]
rate of 17.5% in DHCA (8% permanent, 7.1% temporary, 2.4% SCI) and 18.2% in MHCA (7.8% permanent,
7.1% temporary and 3.3% SCI). The same Authors reported 2,008 cases of elective arch surgery using ACP
[78]
from the same database. Most of the patients were operated on using MHCA and the length of ACP varied
from < 40 min (53.4%) to ≥ 60 min (21.8%) to ≥ 90 min (6.6%). The overall NDs rate was 11.6% (5.1%
permanent, 5.6% temporary and 0.9% SCI), increasing from < 40 min (9.7%) to ≥ 90 min (21.0%).
Multivariate hierarchical regression for moderate hypothermia shows that ACP was safe till 80 min, longer
[49]
than the 65-min CA time demonstrated safe in experiments on pigs .
This concept was questioned by Hughes , who underlined that the lack of clinically evident NDs does not
[79]
reflect the safety of the procedure. The GOT ICE was a randomized study that included detailed
neurocognitive testing and anatomic and functional neuroimaging. It demonstrated that, after total arch
replacement using ACP and three different temperature groups (≤ 20 °C, 20.1-24.0 °C and 24.1-28.9 °C),
there was no difference in clinical outcome. However, cognitive function began to decline when HCA with
ACP lasted > 35 min, suggesting this to be the true safe duration of HCA with ACP. Finally, the study
showed the association of short durations of HCA with significant postoperative reductions in cerebral gray
matter volume, cortical thickness, and regional brain functional connectivity. These findings were
significantly associated with neurocognitive deficits in verbal memory and attention/concentration.
Structural verbal memory showed a significant decline in high MHCA group compared with DHCA group
(P = 0.03).

Anatomy of Willis’ circle
Unilateral perfusion of the brain through the right axillary artery in combination with DHCA or MHCA is a
strategy commonly used in surgical repair of the aortic arch. The contralateral brain is perfused correctly
only if the circle of Willis works well. A study on 250 cadavers and 250 patients undergone brain angio-CT
found that in 58.6% of the cases, there were anatomic conditions for left cerebral hemisphere
[80]
hypoperfusion . As part of the standard preoperative assessment, extracranial and transcranial color-coded
duplex sonography was conducted on 391 patients scheduled for elective arch surgery. UCP could be
defined as safe in 72% of the patients, moderately safe in 18%, and unsafe in 10% . This anatomic aspect
[81]
seems not to translate into a worse cerebral outcome. Two recent pooled analyses, 3,723 patients receiving
[82]
bilateral CP vs. 3,065 patients receiving unilateral CP and 1,894 patients receiving unilateral CP vs. 3,206
patients receiving bilateral CP , showed no difference in the rate of PNDs, in agreement with a recent
[83]
propensity-matched analysis suggesting no neurological benefit of bilateral over unilateral CP in elective
aortic arch surgery . It is possible that bilateral and unilateral CP entail a similar ND rate as the former can
[84]
reduce cerebral damages due to hypoperfusion, but can increase the rate of embolic ND due to epiaortic
vessels manipulation . On the other side, Angeloni et al. observed an increased rate of mortality in UCP
[81]
during circulatory arrest times exceeding 30 min . Jiang et al., in 595 patients with AAD, found that
[82]
patients who received unilateral (n = 276) compared with bilateral CP (n = 319) showed higher rates of NDs
(17.8% vs. 9.4%, P = 0.002), in particular permanent (8.0% vs. 2.8%, P = 0.005) . These findings were not
[85]
confirmed by a meta-analysis from Taosudis et al. and a report by Song et al., who found no difference in
NDs, permanent or temporary, between the two strategies [86,87] . On the contrary, Piperata et al., in patients
operated on for AAD, found a lower rate of permanent NEs where unilateral CP was used (4% vs. 14%,