Neurologic
outcome after aortic arch repair with frozen elephant trunk: The pivotal
role of hypothermic circulatory arrest time
Mostafa
Mousavizadeh1, MD; Mohamad Bashir2*, M.D, Ph.D, MRCS
; Idhrees Mohammed 3, MD; Mahdi
Daliri1, MD; Hadi Abo Aljadayel1,
MD;; Yousef Rezaei1, MD; Saeid
Hosseini1, MD
1Heart
Valve Disease Research Center, Rajaie Cardiovascular Medical and
Research Center, Iran University of Medical Sciences, Tehran, Iran
2Health
Education & Improvement Wales,Wales, UK
3 Institute of Cardiac and Aortic Disorders (ICAD),
SRM Institutes for Medical Science (SIMS Hospital), Chennai, Tamil Nadu,
India
Running title:Frozen
elephant trunk in acute type A dissection
* Corresponding Author:
Mohamad Bashir, MD, PhD, MRCS
Health Education & Improvement Wales,Wales, UK
Email:
drmbashir@gmail.com
Keywords: Aorta, Aortic arch, Dissection, Acute dissection,
Frozen elephant trunk, Meta-analysis
Funding declarations: None to be declared
Conflicts of interest: None to be declared
I have read with great interest, “Neurological complications following
frozen elephant trunk for aortic dissection: What’s truly to blame?”(1)
. Dr. Tan’s comments on our article, “Hypothermic circulatory arrest
time affects neurologic outcomes of frozen elephant trunk for acute type
A aortic dissection: A systematic review and meta-analysis” published
in the Journal of Cardiac Surgery (2).
Frozen Elephant Trunk (FET) was described primarily to treat arch and
proximal descending aorta pathologies in a single-stage approach in
early 2000s (3) and subsequently, evolved with great endeavours through
recent years. The most important advantage of FET is to provide
“hybrid” alternative treatment for complex pathologies which required
two morbid surgeries, formerly. The FET technique has been used in
different aortic pathologies, acute aortic dissection (Stanford Type A
and B, DeBakey I), atherosclerotic arch, descending or thoraco-abdominal
aneurysms and for other pathologies such as penetrating aortic ulcers
(4).
Although outstanding improvements were achieved after introduction of
FET, one of the main serious drawback of this approach is potential
association with neurologic events .The observed discrepancy among rate
of neurologic outcomes including transient or permanent spinal cord
injury (SCI) and stroke after FET deployment in recent reports is
principally attributed to individual cerebral perfusion methods and
cerebral protection techniques. The incidence rate of permanent or
transient ischemic SCI after conventional ET has been reported between
0.4% and 2.8% in previous reports (5). In contrast, the incidence of
SCI after FET ranged between 8% in multicenter studies (6) and 20% in
single-center reports (7). In addition, several contributors (i.e.,
length of the device and distal circulatory arrest time) have been
proposed to explain SCI and stroke observed after FET procedure, mainly
derived from observational studies on patients with diverse aortic
pathologies.
Individual pathologies are inherent with specific risk of post-operative
outcomes after FET procedure, so we decided to adjudicate the pooled
estimated rate of neurologic outcomes in a specific subgroup of patients
diagnosed with acute type A aortic dissection (ATAAD). The present
meta-analysis, including 35 studies with 3211 patients diagnosed with
ATAAD, revealed that the FET procedure in this subset of patients was
associated with 3% (95% CI 2 – 4) and 5% (95% CI 4 – 7) of
postoperative SCI and stroke, respectively. These results are comparable
with recent studies.
Preventza et al explored the role of device length on SCI rate in the
published meta-analysis included all patients who underwent total arch
replacement with FET and concluded that with the extension of stent
beyond T8 is associated with higher risk of SCI (8). In spite of the
fact that surgical methods and stent variations would affect the
outcomes after procedure, intra-operative measures such as HCA time are
of paramount. In a review article, Gupta et al concluded that there are
still debates on the definition of safe HCA time (9). Some endeavors
have been applied to define the type of HCA duration as mild, moderate,
or deep HCA by experts in the field of aortic surgery (9). Future
randomized and prospective studies are required to address this issue
and provide us an appropriate length of HCA for aortic surgeries, and
also show us how we can attenuate neurologic events by some
modifications in surgical modalities, particularly HCA time.
We hypothesized that HCA time is one of major indicator of adverse
neurologic outcomes in FET course of action. The univariate
meta-regression of included patients showed significant relationships
between the HCA time and the development of postoperative stroke (p =
0.04) and SCI (p = 0.05). These findings could be a backbone of future
studies involved in devices’ design and modifications in FET deployment
during surgery. As we revealed in recent meta-analysis that the
anastomosis in Zone 2 was associated with a lower rate of renal failure
compared with Zone 3 (10), this approach might improve neurologic
outcomes by reducing HCA time.
However, the present meta-analysis had several limitations. The studies
analyzed were observational in design, with the inherent bias and the
lack of uniformity in surgical methodology and reporting. The absence of
a standard reporting schema for total arch replacement using FET, some
important data are missing, which incapacitates us to perform subgroup
analysis. Future individual patient’s meta-analysis and/or prospective
randomized reports can help us with the identification of contributors
to the neurologic outcomes and the appraisal of HCA time.