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\begin{document}

\title{Central shunt for tetralogy of Fallot after original Blalock--Tasussig
shunt in a 34-year-old woman}



\author[1]{Keisuke Nakanishi}%
\author[1]{Shiori Kawasaki}%
\author[1]{Atsushi Amano}%
\author[1]{Minoru Tabata}%
\affil[1]{Juntendo Daigaku}%


\vspace{-1em}



  
  \date{May 11, 2024}


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\selectlanguage{english}
\begin{abstract}
A 34-year-old woman presented with original Blalock Taussig shunt and
tetralogy of Fallot. The anastomosis site of the original
Blalock--Taussig shunt revealed stenosis and severe cyanosis. A central
shunt was performed with 6mm artificial vessel, not a radical operation.
After surgery, the cyanosis improved as intended.%
\end{abstract}%



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\textbf{Introduction}

The Blalock--Taussig (BT) shunt in the tetralogy of Fallot was first
performed in 1946. {[}1{]} It has been improved to create a short
circuit in the pulmonary artery by using an artificial blood vessel.
Spontaneous prognosis after only this surgery is poor, and radical
surgery is necessary to improve the long-term prognosis. However, for
various reasons, some patients have only undergone surgery and not any
therapeutic intervention. In this report, we describe a case of central
shunt surgery to improve cyanosis in a patient who had been followed-up
for a long time without radical surgery after an original BT shunt.

\textbf{Case report}

The patient was a 34-year-old woman (weight, 38.3 kg; height, 150 cm;
BSA, 1.29) who had been diagnosed at birth with tetralogy of Fallot on
the basis of severe cyanosis. The original m-BT shunt on the left was
performed at the age of 2 years. During outpatient follow-up, the
patient fell down the stairs and suffered a cervical spinal injury.
Recently, however, cyanosis has progressed rapidly during physical
movement, and we decided to treat her with surgery. The patient's
physical activities of daily living had decreased significantly, and
there was concern about pulmonary artery hypoplasia; therefore, it was
thought that the patient would not tolerate radical surgery.
Preoperative contrast-enhanced computed tomography (CT) revealed
stenosis of the subclavian artery at the anastomosis to the pulmonary
artery and complete occlusion of the right ventricular outflow tract.
(Figure 1 a) In surgery, dissection was performed through a midline
incision approach as usual, and after establishing an artificial
heart-lung machine with ascending aortic blood supply and right atrial
debridement, a short circuit was created from the ascending aorta to the
main pulmonary artery using a 6 mm artificial vessel. (Figure 2) The
patient was easily weaned from cardiopulmonary bypass and had a good
course of postoperative ICU management. The patient was weaned from the
ventilator on the first postoperative day, and subsequent rehabilitation
progressed smoothly despite the paralysis. Postoperatively, her SpO2
increased to 80\% and her preoperative symptoms, such as decreased SpO2
with light exertion, improved. Postoperative contrast-enhanced CT showed
that blood flow to the shunt and pulmonary artery was maintained.
(Figure 1 b)

Discussion

The BT shunt was originally designed and performed to improve cyanosis
in the tetralogy of Fallot, but it is not curative, and the pulmonary
artery blood flow rate decreases as the body grows. In fact, the
survival rate at 25 years after surgery of patients with tetralogy of
Fallot who underwent palliative surgery only is approximately 50\%.
{[}2{]} There have been almost no case reports of palliative central
shunting in adulthood, {[}3{]} and we report here another case in which
cyanosis was improved in adulthood after central shunting.

The concerns in this case were the development of postoperative
congestive heart failure and hypercapnic lung injury. {[}4{]} Shunt
reduces blood flow to the body and increases pulmonary blood flow,
thereby increasing Qp/Qs as a surgical procedure. Although it is
difficult to accurately evaluate preoperatively whether the patient's
heart tolerates congestive heart failure, the 6 mm artificial vessel
used in this study did not progress to heart failure due to low blood
flow, although the postoperative lungs showed temporary lung damage due
to high pulmonary blood flow.

The second concern is the patency of artificial blood vessels. In
general, there are many reports on the patency of artificial vessels in
FP bypass, but there are no reports on the patency of the central shunts
in adulthood. The shorter distance of the artificial vessel and its
higher blood flow rate in this procedure may be expected to result in a
higher patency rate than that of FP bypass; however, this has not been
clearly confirmed.

Central shunting was effective in improving SpO2 in adult patients;
however, there are many uncertainties regarding postoperative
hemodynamics.

\textbf{List of Abbreviations}

BT, Blalock---Tasussig

CT, computed tomography

\textbf{DeclarationsEthics and Consent to Participate}The study was
approved by the ethics review board of our institution, and the patient
provided written informed consent for the publication of this
case.\textbf{Consent for Publication}Not applicable\textbf{Data
Availability Statement}Not applicable\textbf{Conflicts of
Interest}None.\textbf{Financial Support}This research received no
specific grants from any funding agency, commercial, or not-for-profit
sectors.\textbf{Authors' Contributions}Conception and design of study:
KN, SK; Drafting the manuscript: KN revising the manuscript critically
for important intellectual content: KN, SK, AA Approval of the version
of the manuscript to be published: AA, MT



\textbf{References}

\begin{enumerate}
\tightlist
\item
  Blalock A. The Surgical Treatment of Congenital Pulmonic Stenosis.
  Annals of Surgery. 1946;124;879-885.
\item
  Presbitero P, D'Antonio P, Brusca A, Mores M. Prognosis of Fallot's
  Tetralogy after Palliative Operations : 10-25 Year Follow-up. Ped
  Cardiol. 1983;4:175-182.
\item
  Peries A, Al-Hay AAA, Shinebourne EA. Outcome of the construction of a
  Blalock--Taussig shunt in adolescents and adults. Cardiol Young
  2005;15:368--372
\item
  Yang J, He BC, Chen JM, Cen JZ, Wen SS, Xu G, et al. Results of
  surgery on adults with functional single ventricle without prior
  cardiac surgery in childhood. J Card Surg. 2019;34:1556--1562.
\end{enumerate}

\textbf{Figure legends}

\textbf{Figure 1}

a: Subclavian artery stenosis at the anastomosis to the pulmonary artery
and complete occlusion of the right ventricular outflow tract. b: Blood
flow to the shunt and pulmonary artery was preserved.

\textbf{Figure 2}

a systemic pulmonary shunt was created from the ascending aorta to the
main pulmonary artery using a 6 mm artificial vessel.\selectlanguage{english}
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\includegraphics[width=0.70\columnwidth]{figures/Figure-2/Figure-2}

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