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\begin{document}

\title{Intraoperative Epicoronary Ultra-High Frequency Ultrasound in Coronary
Artery Bypass Grafting Surgery}



\author[1]{Ashley Fritz}%
\author[1]{Archer Martin}%
\author[2]{Erol Belli}%
\author[1]{Steven Clendenen}%
\affil[1]{Mayo Clinic}%
\affil[2]{University of South Florida}%


\vspace{-1em}



  
  \date{June 16, 2024}


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\selectlanguage{english}
\begin{abstract}
The use of intraoperative epicardial ultrasound in order to aid
physicians and surgeons in open cardiac surgery has been established for
quite some time. Recently, the development of ultra-high frequency
ultrasound (UFHUS) technology has resulted in high-resolution imaging
capabilities previously unavailable for clinical use. This report is the
first to describe the use of intraoperative UFHUS epicoronary scanning
to assess coronary anatomy and visualize cardioplegia flow within native
coronary vessels.%
\end{abstract}%



\sloppy


\textbf{Case Report:}

The use of intraoperative epicardial ultrasound to scan coronary
arteries in order to assess bypass graft targets and survey efficacy of
surgical re-vascularization is well described within the literature.(1)
Whereas the international Registry for Quality Assessment with
Ultrasound Imaging and TTFM in Cardiac Bypass Surgery (REQUEST) trial
utilized a 15 Mhz probe for scanning, recent literature describes the
use of an ultra-high frequency ultrasound (UHFUS) 70 Mhz probe for
anatomical assessment during non-cardiac surgery.(1, 2) We present a
case of intraoperative UHFUS use for epicoronary scanning in a patient
undergoing coronary artery bypass grafting (CABG) surgery. The patient
gave written permission to publish this case.

A 64 year old male with a past medical history significant for
hypertension and hyperlipidemia was referred to our service for
evaluation of his coronary artery disease. He reported worsening chest
pain with activity over the year prior to referral, and was evaluated
pre-operatively with both non-invasive and invasive cardiac testing.
Transthoracic echocardiography showed concentric left ventricular
hypertrophy with intact biventricular function. Left heart
catheterization showed extensive coronary disease including 95\% left
main coronary occlusion, multiple discrete left anterior descending
(LAD) coronary occlusions ranging from 50\%-100\%, and a 90\% right
coronary artery (RCA) lesion. The patient was scheduled for an on-pump
CABG surgery.

The patient was brought to the operating room where he was placed under
general anesthesia. After median sternotomy was performed, harvesting of
saphenous vein and bilateral mammary arteries commenced without event.
Both antegrade and retrograde cardioplegia were used to ensure
electromechanical silence of the heart during cardiopulmonary bypass. A
70 Mhz UFHUS probe was employed to assess the surface anatomy of the
native, diseased coronary arteries in order to optimize anatomical
planning for graft targets. After being placed in a sterile sleeve, the
probe was used to assess the LAD and posterior descending artery (PDA).
As noted in figure 1 and video 1, both cardioplegia flow and significant
calcifications were seen in the PDA. Figure 2 shows the LAD in short
axis, and calcifications are noted for both their bright echogenicity
and ultrasonic dropout artifact. Coronary grafting commenced and a
Doppler flowmeter was used to confirm patency. The patient had a
successful separation from cardiopulmonary bypass, uneventful
post-operative course, and was discharged on post-operative day seven.

\textbf{Discussion:}

The REQUEST trial reported that the use of high-frequency ultrasound
(HFUS) is not only helpful for evaluating coronary targets, but that
physicians should consider incorporating it into their usual practice
for CABG surgery.(1) Higher frequency probes (55 Mhz) have been used to
examine temporal arteries in the setting of Giant Cell disease, with
greater resolution allowing for accurate assessment of intima layer
thickness that correlated with histological diagnosis.(3)

As the probe frequency increases, image resolution improves while sound
penetration decreases.(2) Therefore, the use of UFHUS for epicoronary
scanning presents a theoretical benefit over lower-frequency probes, yet
no comparison of image quality was performed during this case. While our
probe was rated up to 70 Mhz frequency, a frequency of 50 Mhz was used
in order to achieve appropriate ultrasound penetration depth of 5.5mm
for epicoronary scanning. In our case, the UFHUS allowed for real-time
evaluation of the extensive native coronary calcification during
cardiopulmonary bypass. It can often be challenging to assess this in an
arrested heart, and inadvertent selection of a distal graft site with
heavy calcification requiring endarterectomy may lead to lower long-term
patency. In addition to serving as an imaging aid for selection of
acceptable graft target sites, other potential applications of UFHUS
epicoronary scanning include confirming cardioplegia flow in the setting
of low coronary sinus pressures and appraising distal coronary flow
post-revascularization.

To our knowledge, this is the first report of the use of UFHUS for
epicoronary scanning in CABG surgery. Further study is necessary to
compare the efficacy of UFHUS versus high frequency ultrasound for use
in epicoronary scanning during CABG surgery.

\textbf{Figure Legend:}

\textbf{Figure 1:} Short axis view of the posterior descending artery.
Note the significant calcifications and subsequent acoustic shadowing. A
branch of the middle cardiac vein is present on the right side of the
picture.

\textbf{Video 1:} This video shows the presence of retrograde
cardioplegia flow within the cardiac arterial and venous system during
cardiopulmonary bypass.

\textbf{Figure 2:} Short axis view of the left anterior descending
artery. The arrows points to the presence of calcification.
Additionally, intraluminal irregularities are noted within the artery.

\textbf{References:}

1. Taggart DP, Thuijs D, Di Giammarco G, Puskas JD, Wendt D, Trachiotis
GD, et al. Intraoperative transit-time flow measurement and
high-frequency ultrasound assessment in coronary artery bypass grafting.
J Thorac Cardiovasc Surg. 2019.

2. Boczar D, Forte AJ, Oliver JD, McClain RL, Murray P, Clendenen SR.
Intraoperative evaluation of cervical nerve root avulsion using
ultra-high-frequency ultrasound system. Case Reports Plast Surg Hand
Surg. 2019;6(1):43-6.

3. Sundholm JKM, Paetau A, Alback A, Pettersson T, Sarkola T.
Non-Invasive Vascular Very-High Resolution Ultrasound to Quantify Artery
Intima Layer Thickness: Validation of the Four-Line Pattern. Ultrasound
Med Biol. 2019;45(8):2010-8.\selectlanguage{english}
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\includegraphics[width=0.70\columnwidth]{figures/Image-1/Image-1}

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\includegraphics[width=0.70\columnwidth]{figures/Image-2/Image-2}

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\textbf{Hosted file}

\verb`Video 1.mov`  available at \url{https://authorea.com/users/330544/articles/457294-intraoperative-epicoronary-ultra-high-frequency-ultrasound-in-coronary-artery-bypass-grafting-surgery}

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