Optimal bypass graft design for left anterior descending and diagonal territory in multivessel coronary disease
Sachi Koyama
2
4
Keiichi Itatani
3
4
Tadashi Yamamoto
0
Shohei Miyazaki
3
Tadashi Kitamura
4
Tuyoshi Taketani
1
Minoru Ono
2
Kagami Miyaji
4
0
Department of Cardiology, Hokkaido Cardiovascular Hospital
, Hokkaido,
Japan
1
Department of Cardiovascular Surgery, Mitsui Memorial Hospital
, Chiyoda,
Tokyo, Japan
2
Department of Cardiac Surgery, Graduate School of Medicine, The University of Tokyo
, Bunkyo,
Tokyo, Japan
3
Department of Hemodynamic Analysis, Kitasato University School of Medicine
, Sagamihara, Kanagawa,
Japan
4
Department of Cardiovascular Surgery, Kitasato University School of Medicine
, Sagamihara, Kanagawa,
Japan
OBJECTIVES: Coronary artery bypass grafting for multivessel disease requires an appropriate graft design to avoid the competition of flow between the graft and the native vessel in order to achieve a sufficient coronary flow and durable graft patency. METHODS: Three-dimensional computational models of the left coronary artery were created based on the angiographic data. Three stenosis patterns of 75 and 90% combinations were created in the left anterior descending artery (LAD), the diagonal branch (Dx) and the circumflex artery (LCx). The left internal thoracic artery (LITA) was anastomosed to the LAD, and separate saphenous vein grafts (SVGs) were anastomosed to the Dx and the LCx in the 'Independent' model. The 'Sequential' model included sequential SVG anastomoses to the Dx and the LCx with a left internal thoracic artery-left anterior descending artery bypass, and Y-composite arterial grafts to LAD and Dx were created in the 'Composite' model. RESULTS: The 'Independent' model had high reverse flow from the Dx to the LAD in systole, resulting in decreased LITA flow when Dx stenosis was mild. The 'Sequential' model also had reverse flow in diastole, resulting in additional LAD flow. The 'Composite' model distributed increased flow to the Dx when Dx stenosis was severe, resulting in decreased flow to the LAD. CONCLUSIONS: Systematic flow evaluation is beneficial for determining the optimal bypass graft arrangement in patients with multivessel disease. Individual SVG anastomoses to the Dx and the LCx are not desirable when Dx stenosis is not severe and a Y-composite arterial graft to the LAD and the Dx is not desirable when Dx stenosis is severe.
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The increase in life expectancy has confronted cardiac surgery
with a rapidly growing population of elderly patients requiring
surgical myocardial revascularization [1]. A fundamental aim of
coronary surgery is to fashion a perfect anastomosis to deliver
blood flow to the ischaemic territories of the myocardium with
durable graft patency [2]. However, the ideal designing of coronary
revascularization is uncertain, especially in cases with multivessel
disease because the competitive flow between the graft and the
native vessels, which is closely related to long-term graft patency
[3], is difficult to predict. The blood flow distribution from each
graft needs to be taken into consideration to provide adequate
blood supply to the ischaemic territory.
Recently, several attempts have been made to evaluate coronary
artery diseases using computational fluid dynamics (CFD), which is
considered to be a novel method that can predict blood flow and
pressure from the cardiovascular system [4]. The CFD method
enables the quantitative evaluation of the severity of coronary
ischaemia based both on the anatomical features of the disease site
and on the myocardial reserve of the perfused lesion in each branch.
Taylor et al. developed the fractional flow reserve derived from
coronary computed tomography (CT) angiography, a noninvasive
method for identifying ischaemia-causing stenosis [5], and Samady
et al. calculated the wall shear stress in the disease site to evaluate
the risk of plaque rupture and progression [6]. This method has the
potential to provide a systematic evaluation of complicated
cardiovascular diseases, and can facilitate graft design definition for treating
multivessel disease.
The objective of this study was to establish the optimal graft
arrangement for the left anterior descending and the diagonal
territory in multivessel disease. To fulfil this objective, we
developed idealized 3D CFD models that enable the systematic
evaluation of blood flow and pressure distribution of each native
The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
branch and grafted vessel in various types of coronary artery
bypass grafting (CABG).
The present study was based on CFD models with basic idealized
geometry to examine the details of the haemodynamics in
patients with coronary artery disease before and after bypass
graft procedures. The analysis involved the following three steps:
firstly, 3D coronary arterial models were constructed using the
computer-assisted design (CAD) technique. Models of three types
of coronary artery disease and three types of bypass gr (...truncated)