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\begin{document}

\title{Routine Pre-operative CT - ready to roll or a step too far?}



\author[1]{Pradeep Narayan}%
\author[2]{Gianni Angelini}%
\affil[1]{Rabindranath Tagore International Institute of Cardiac Sciences}%
\affil[2]{Bristol University}%


\vspace{-1em}



  
  \date{May 23, 2024}


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\selectlanguage{english}
\begin{abstract}
The incidence of stroke after coronary artery bypass grafting (CABG) is
around 1.3\% in the Society of Thoracic Surgeons database but carries a
mortality of almost 20\% (1,2). The stroke rate is even higher with
aortic valve replacements with the Determining Neurologic Outcomes from
Valve Operations (DeNOVO) study reporting stroke rates as high as 17\%
(3). It is also likely that variations in definition of stroke leads to
underreporting of this event. There is thus, no denying that stroke
remains the Achilles heel of cardiac surgery and efforts must be made to
mitigate its occurrence.%
\end{abstract}%



\sloppy


\textbf{Routine Pre-operative CT - ready to roll or a step too far?}

Pradeep Narayan FRCS{[}CTh{]}*, Gianni D Angelini FRCS\^{}

* Rabindranath Tagore International Institute of Cardiac Sciences,
Narayana Health, India

\textbf{Word Count} : 1038

\textbf{Corresponding Author:}

Prof GD Angelini, MD,MCh,FRCS, FMedSci

British Heart Foundation Professor of Cardiac Surgery,

Bristol Heart Institute Bristol Royal Infirmary,

Upper Maudlin Street~BS2 8HW

Bristol, UK

G.D.Angelini@bristol.ac.uk

\textbf{Conflict of Interest} : none

\textbf{Funding:} This work was supported by the British Heart
Foundation and the NIHR Biomedical Research Centre at University
Hospitals Bristol and Weston NHS Foundation Trust and the University of
Bristol.

\textbf{Key words} : Pre-operative CT, Stroke, CABG

The incidence of stroke after coronary artery bypass grafting (CABG) is
around 1.3\% in the Society of Thoracic Surgeons database but carries a
mortality of almost 20\% (1,2). The stroke rate is even higher with
aortic valve replacements with the Determining Neurologic Outcomes from
Valve Operations (DeNOVO) study reporting stroke rates as high as 17\%
(3). It is also likely that variations in definition of stroke leads to
underreporting of this event. There is thus, no denying that stroke
remains the Achilles heel of cardiac surgery and efforts must be made to
mitigate its occurrence.

The case by Osorio-Jaramillo published in this issue of the journal
reignites the discussion on the value of computerised tomographic(CT)
imaging as a routine pre-operative investigation prior to cardiac
surgery (4). The identification of a mass on the ascending aorta led to
a revision in operative strategy whereby along with the initially
planned CABG, concomitant supra-coronary replacement of the ascending
aorta was also performed. It is likely that in the absence of
modification of surgical strategy this unexpected mass in the ascending
aorta may have led to a peri-operative stroke with serious adverse
outcomes.

Atheromatous disease of the aorta not only increases the risk of
perioperative stroke but also impacts upon long term mortality (5--7).
The stroke rate has been shown to be quadrupled in presence of an
atheroma in the proximal aorta (5). Prevention of these adverse outcomes
thus hinges on identification of the atheromatous aorta. While this has
been attempted intra-operatively by manual palpation of the aorta the
reliability with manual palpation is low with the additional risk of
plaque embolization.(7,8) Trans-Esophageal-Echocardiography(TEE) has
also been used to detect atherosclerotic aorta but has limited access to
the ascending aorta and arch and the sensitivity is only marginally
better than manual palpation (9). Epi-aortic ultrasound is significantly
better than both manual palpation and TEE and is recommended for
identification of atheromatous plaques (Class IIa, level of evidence C)
(10) The downside of Epi-aortic ultrasound is it being operator
dependent and more importantly the information is available only after a
sternotomy has been performed. Pre-operative planning and a considered
discussion with the patient is thus not possible. Multidetector computed
tomography (MDCT) is being used increasingly to diagnose the
atheromatous aorta and its superior spatial resolution coupled with 3D
reconstruction capabilities makes it an attractive option in the
pre-operative setting (11).

Preoperative CT has been used in the past predominantly in the
re-operative setting. Studies comparing patients undergoing re-operative
surgery have reported a reduction in stroke rates in patients undergoing
preoperative CT scans (12). Apart from stroke there was also a reduction
in sternotomy-related injury, complication rates (13,14) and this
resulted in improved perioperative outcomes (15). There are
contradictory findings with regards the effect of pre-operative CT scans
on mortality with some studies suggesting improved outcomes(13,15) while
others suggest an increase of mortality in these patients(12). While the
findings of all these studies may be influenced by several factors and
are open to questioning one fact remains indisputable that most studies
report a change in either surgical access, strategy of cannulation or
even operability(16). While the indication for a preoperative CT in
re-operative surgery is essentially to assess the anatomical orientation
of structures and especially the grafts after CABG; its role in primary
cardiac surgery is to evaluate the extent of atherosclerosis of the
ascending aorta and arch (16).

While the usefulness of pre-operative CT scan is intuitive, robust data
on improvement with this strategy is sparse, especially in routine or
low-risk patients. In high-risk patients use of pre-operative CT scan in
patients undergoing cardiac surgery has been shown to be associated with
a reduction in stroke rates as well as mortality (17). However, the
groups compared were from two different time periods. Another study that
carried out pre-operative CT scan in patients undergoing CABG except
those who required emergency surgery or had renal failure demonstrated a
change of strategy in nearly half the patients (18). The change in
strategy included avoidance of cannulation and cross-clamping by using
off -pump anaortic techniques, alteration in conduit selection and
grafting strategy, as well as replacement of ascending aorta and
additional procedures on the carotid and renal arteries. Besides,
pre-operative CT identified malignancy in some patients as well.

The concerns with using pre-operative CT scans include radiation
exposure, contrast induced nephropathy, additional cost and utilization
of resources which may be an important consideration in resource
depleted countries and state funded healthcare systems. Even though,
ultra-low-dose CT scanning without contrast enhancement can
satisfactorily identify an atheromatous aorta thus ameliorating some of
the concerns the benefit of pre-operative CT scan is still not
established. Studies which have compared the role of pre-operative CT in
improving outcomes especially in primary surgery are few and suffer from
considerable heterogeneity.

While some of the studies have used contrast enhanced CT scans other use
non-contrast CT for reporting outcomes. Considerable variability also
exists in the case-mix with CABG, valve surgeries and CABG with
concomitant valve surgery being included in varying proportions in
different studies all of which further muddy the water. Mortality has
been defined at 30-day in some and as in-hospital in others making
comparison across studies extremely unreliable. The definition of stroke
in these studies still needs to be standardized. The current definition
of stroke as recommended by the new American Heart Association/American
Stroke Association statement has modified the definition such that in
addition to clinical features of stroke, evidence of cerebral emboli by
diffusion-weighted magnetic resonance imaging also constitutes stroke
(19).

Pre-operative CT scans have shown potential and should not be dismissed
however, large scale randomized studies would be needed to confirm its
place in routine pre-operative evaluation of cardiac surgical
procedures. The results of ``Ultra low-dose chest CT with iterative
reconstructions as an alternative to conventional chest x-ray prior to
heart surgery (CRICKET study)'' are awaited (NCT02173470). The study is
a multi-centric randomized controlled trial comparing pre-operative
Chest X-rays and those undergoing an additional pre-operative
non-contrast-enhanced chest CT among patients undergoing cardiac surgery
(20). The outcomes studied include stroke rate and alteration of
surgical strategy. Until the time more conclusive evidence is available,
routine pre-operative CT scans seems a step too far and can perhaps only
be justified in re-operative surgery and in patients at high risk for
developing a peri-operative neurological event.

References:

1. Gaudino M, Angiolillo DJ, Di Franco A, Capodanno D, Bakaeen F,
Farkouh ME, et al. Stroke After Coronary Artery Bypass Grafting and
Percutaneous Coronary Intervention: Incidence, Pathogenesis, and
Outcomes. Journal of the American Heart Association. 2019 Jul
2;8(13):e013032.

2. O'Brien SM, Feng L, He X, Xian Y, Jacobs JP, Badhwar V, et al. The
Society of Thoracic Surgeons 2018~Adult Cardiac Surgery Risk
Models:~Part~2-Statistical Methods and~Results. Ann Thorac Surg. 2018
May;105(5):1419--28. 1.

3. Mess\selectlanguage{ngerman}é SR, Acker MA, Kasner SE, Fanning M, Giovannetti T, Ratcliffe
SJ, et al. Stroke after aortic valve surgery: results from a prospective
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4 Osorio-Jaramillo E, Strassl A, Kocher A, Laufer G, Haberl T.
Nose-shaped Mass in the Ascending Aorta. J Card Surg. 2022;

5. Roach GW, Kanchuger M, Mangano CM, Newman M, Nussmeier N, Wolman R,
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6. Butler CG, Ho Luxford JM, Huang C-C, Ejiofor JI, Rawn JD, Wilusz K,
et al. Aortic Atheroma Increases the Risk of Long-Term Mortality in
20,000 Patients. Ann Thorac Surg. 2017 Oct;104(4):1325--31.

7. Andersen ND, Hart SA, Devendra GP, Kim ESH, Johnston DR, Schroder JN,
et al. Atheromatous disease of the aorta and perioperative stroke. J
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8. Royse AG, Royse CF. Epiaortic ultrasound assessment of the aorta in
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9. Suvarna S, Smith A, Stygall J, Kolvecar S, Walesby R, Harrison M, et
al. An Intraoperative Assessment of the Ascending Aorta: A Comparison of
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10. Sousa-Uva M, Neumann F-J, Ahlsson A, Alfonso F, Banning AP,
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11. Akhtar NJ, Markowitz AH, Gilkeson RC. Multidetector computed
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13. Aviram G, Mohr R, Sharony R, Medalion B, Kramer A, Uretzky G. Open
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16. den Harder AM, de Heer LM, Meijer RCA, Das M, Krestin GP, Maessen
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18. Park K-H, Lee HY, Lim C, Chung ES, Sung S-W, Choi SI, et al.
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19. Sacco RL, Kasner SE, Broderick JP, Caplan LR, Connors JJB, Culebras
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20. den Harder AM, de Heer LM, Maurovich-Horvat P, Merkely B, de Jong
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