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\begin{document}

\title{Right Anterior Minithoracotomy for Redo Aortic Valve Replacement After
Coronary Artery Bypass Grafting with Bilateral Internal Thoracic Artery:
a Case Report}



\author[1]{Hironobu Nishiori}%
\author[1]{Tomoki Sakata}%
\author[1]{Goro Matsumiya}%
\affil[1]{Chiba Daigaku Igakubu Fuzoku Byoin}%


\vspace{-1em}



  
  \date{May 12, 2024}


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\selectlanguage{english}
\begin{abstract}
A 63-year-old male, with a history of coronary artery bypass grafting
using bilateral internal thoracic artery grafts, underwent surgical
aortic valve replacement. Avoiding the graft injury, we selected the
right anterior mini-thoracotomy approach under cardiac arrest with
systemic hyperkalemia with remaining bilateral internal thoracic artery
grafts open. Deep hypothermia was induced to obtain more reliable
myocardial protection. We believe this strategy can be considered as a
therapeutic option in patients requiring aortic valve replacement but
unsuitable for transcatheter aortic valve replacement.%
\end{abstract}%



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\textbf{Introduction}

The operative risk of aortic valve replacement (AVR) after coronary
artery bypass grafting (CABG) is known to be high because graft may be
injured by median sternotomy, leading to serious myocardial ischemia and
resultant poor prognosis.\textsuperscript{1} Moreover, in some cases,
trans-catheter aortic valve replacement (TAVR) after CABG can not be
selected for various reasons, and surgical AVR must be
performed.\textsuperscript{2} In such situations, myocardial protection
during cardiac surgery is an important point of discussion, and some
unique methods have been reported to avoid graft
damage.\textsuperscript{3} We experienced a case of AVR through right
lateral mini-thoracotomy after CABG with the bilateral internal thoracic
artery (ITA) grafts. As the grafts were patent and native coronary
arteries were totally occluded, systemic hyperkalemia and deep
hypothermia were utilized to induce cardiac arrest and maintain adequate
myocardial protection without touching the bilateral ITA grafts. Herein
is reported the methods and cautions in this strategy. We have obtained
the consent of the patient for publication.

\textbf{Case Description}

A 63-year-old man, who underwent CABG 10 years ago, was admitted to our
hospital with chief complaints of dyspnea and chest pain. The
transthoracic echocardiography showed aortic valve area of 0.66 cm2,
transvalvular peak velocity of 3.4 m/sec, mean transvalvular pressure
gradient of 28 mmHg, and left ventricular ejection fraction of 44\%, and
he was diagnosed as severe aortic valve stenosis. In the previous CABG,
the right and left ITAs were anastomosed to the anterior descending
artery diagonal artery, respectively. The radial artery was utilized as
Y-graft and anastomosed to the posterior lateral and descending branches
sequentially. The computed tomography imaging revealed that right ITA
crossed over the ascending aorta (Fig.1). The right ITA appeared to be
heavily adherent to the sternum (Fig.2). The coronary angiography showed
the native left and right coronary arteries were all occluded proximally
while all grafts were patent. Moreover, the right ventricular branches
were not visualized even from the graft (Fig. 3A, 3B). We decided to do
surgical AVR with right anterior thoracotomy. TAVR was not selected
since the patient was young enough and had a long life expectancy,
surgical AVR seemed appropriate considering the durability of the
prosthetic valve.

A 7-cm skin incision was placed at the third right intercostal space,
and the ascending aorta was exposed. The cardiopulmonary bypass (CPB)
was established between the right axillary artery and the right femoral
vein. The bilateral ITA grafts were neither touched nor clamped. After
ventricular fibrillation induced by systemic cooling, the aorta was
cross clamped. Potassium was administered at the dose of 40 mEq via the
CPB. The potassium level elevated to 8.7 mEq/dL and cardiac arrest was
obtained. We maintained the patient's body temperature deep enough at 19
degrees Celsius. Additional 40 mEq potassium was administered twice,
targeting potassium level 7.0 to 8.0 mEq/dL. A 21 mm Magna Ease (Edwards
Lifescience Corporation, Irvine, CA, USA) was implanted. The potassium
level was normalized with administration of glucose and insulin and
extracorporeal ultrafiltation method during CPB. After rewarming, the
aorta was de-clamped. The CPB was successfully weaned off. The
postoperative course was uneventful and the patient was discharged on
the postoperative Day 18 after rehabilitation. Two years after the
operation, follow-up transthoracic echocardiography showed an improved
ejection fraction of 54\%, and no para-valvular leakage.

\textbf{Comment}

The number of patients who require aortic valve replacement (AVR) for
severe aortic stenosis (AS) has been increasing.\textsuperscript{1} When
performing re-do AVR after CABG, clamping bypass grafts through median
sternotomy used to be performed for sufficient myocardial protection.
However, this measure imposes high risk due to severe adhesion of the
patent grafts, and graft injury occurs in 5 to 50\% of cases, which
leads to a poor prognosis.\textsuperscript{2.4} This makes redo-AVR
challenging, with a surgical mortality rate of
6-16\%.\textsuperscript{2.5} Kaneko et al.\textsuperscript{3} introduced
the right intercostal approach for re-do AVR after CABG with the patent
left ITA. Cardioplegia was not used to avoid incomplete cardiac arrest
due to washout from patent ITAs. The blood supply was completely
graft-dependent and the native coronary arteries were totally occluded,
therefore, it was theoretically possible to operate under beating
condition. However, considering the impaired ejection fraction due to
coronary arterial disease, cardiac arrest was chosen, which provides
more reliable myocardial protection. In addition, as the right
ventricular branch was not adequately contrasted in the preoperative
coronary angiography, deep hypothermia was induced at 19\selectlanguage{ngerman}°C to minimize
myocardial oxygen consumption in case of poor right ventricular
perfusion. Deep hypothermia at 19 °C can achieve reduced myocardial
oxygen consumption by 45\% compared to at 28°C.\textsuperscript{7}

TAVR might be an alternative option in patients with a history of CABG.
However, the long-term results and the durability of the valve remains
unclear. Surgical AVR is required after TAVR in some situations
including structural valve degeneration, para-valvular leakage, and
complications of TAVR. Fukuhara and his
colleagues\textsuperscript{2}reported that 1\% of patients required TAVR
explantation within eight years after TAVR, more than the number of
patients who had redo TAVR. Therefore, we believe it is essential for
surgeons to understand the strategy for surgical AVR as a therapeutic
option in post CABG patients.

\textbf{References}

1. Byrne JG, Karavas AN, Filsoufi F, et al. Aortic valve surgery after
previous coronary artery bypass grafting with functioning internal
mammary artery grafts. Ann Thorac Surg. 2002;73:779--784.

2. Fukuhara S, Brescia AA, Shiomi S, et al. Surgical explantation of
transcatheter aortic bioprostheses: Results and clinical implications. J
Thorac Cardiovasc Surg. 2021;162(2):539-547.e1.

3. Kaneko T, Nauta F, Borstlap W, McGurk S, Rawn JD, Cohn LH. The
''no-dissection'' technique is safe for r eoperative~aortic
valve~replacement~with a patent left internal thoracic artery graft. J
Thorac Cardiovasc Surg 2012;144:1036-1040.

4. Masaki N, Ogasawara T, Kawarai S, Matsuki K. Aortic valve replacement
for patients with functioning internal mammalian artery grafts. Ann
Thorac Cardiovasc Surg. 2018;24:103-105.

5. Nishi H, Mitsuno M, Yamamura M, et al. Safe approach for redo
coronary artery bypass grafting-preventing injury to the patent graft to
the left anterior descending artery. Ann Thorac Cardiovasc Surg.
2010;16:253-258.

6. Odell JA, Mullany CJ, Schaff HV, et al. Aortic valve replacement
after previous coronary artery bypass grafting. Ann Thorac Surg 1996;
62: 1424-1430.

7. Rousou JH, Engelman RM, Dobbs WA, et al. The optimal potassium
concentration in cardioplegic solutions. Ann Thorac Surg. 1981;32:75-79.

\textbf{Figure legends}

Fig. 1 Preoperative computed tomography image showing LITA and RITA
runing just under the sternal midline and appear to be adherent to the
sternum. (yellow arrows)

LITA: left internal thoracic artery RITA: right internal thoracic artery

Fig. 2 Preoperative computed tomography image showing that RITA run
across the ascending aorta (arrow)

RITA: right internal thoracic artery

Fig. 3 Preoperative coronary angiography showing RITA anastomosed to LAD
(A), LITA and RA were composed as Y-graft, with LITA anastomosed to Dx,
and RA to PL and PD sequentially. The right ventricular branches are not
adequately contrasted, which compromise the right ventricular myocardial
perfusion if cardioplegia is used. (B)

Dx: diagonal branch \begin{CJK}{UTF8}{gbsn}　 \end{CJK}\selectlanguage{english}LAD: left anterior descending LITA: left internal
thoracic artery\begin{CJK}{UTF8}{gbsn}　 \end{CJK}\selectlanguage{english}PD: posterior descending branch\begin{CJK}{UTF8}{gbsn}　　\end{CJK}\selectlanguage{english}PD: posterior
descending branch\begin{CJK}{UTF8}{gbsn}　 \end{CJK}\selectlanguage{english}PL: posterior lateral \begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}RA: radial artery \begin{CJK}{UTF8}{gbsn}　\end{CJK}\selectlanguage{english}RITA:
right internal thoracic artery\selectlanguage{english}
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