252
A. Totorean et al.
Stent overlap is associated with impaired clinical and angiographic outcomes
at follow-up, regardless of stent type and overlap pattern. Stent thrombosis and
restenosis rates proved to be higher than in the case of single stent implantation
for both bare metal stents (BMS) and drug eluting stents (DES) and studies report
the following mechanisms as major determinants: incomplete or delayed endothelialization, incomplete strut coverage, increased vascular injury and inflammation,
or stent fracture. The impact of these phenomena translates clinically into increased
risk of repeat revascularization, myocardial infarction and even death [1, 2].
Wall Shear Stress (WSS) has been widely recognized as a key factor in both
atherogenesis and thrombosis processes [3]. Regions along the arteries walls associated with low WSS are prone to atherosclerotic plaque formation and neointimal
hyperplasia leading to in-stent restenosis, whereas high WSS seems to modulate
stent thrombosis [3–5].
Investigating the hemodynamic environment within a vascular segment is possible
using computational fluid dynamics (CFD) techniques. These methods permit the
analysis and description of near-wall flow patterns, WSS distribution, recirculation
zones, etc., for either native or stented coronary arteries [3–5].
Previous studies used CFD to investigate the hemodynamics associated with overlapping stents. These studies showed that the regions within the vessel exposed to the
overlapping segments are subjected to development of extended recirculation zones,
which associate increased size areas of low WSS, compared to the proximal or distal
parts of the stents not affected by overlap. These hemodynamic disturbances affect
drug distribution, concentration and drug wall uptake for drug eluting stents, delay
endothelial healing, promote platelet deposition and chronic inflammation regardless of stent type, and lead to increased risk for either stent thrombosis or in-stent
restenosis and lumen loss [6, 7].
The aim of this paper to investigate the near-wall flow behavior in case of
overlapping stents for an idealized 2D stented coronary model by analyzing and
describing the associated WSS distribution and recirculation zones, but also further
hemodynamic parameters like pressure distribution, using CFD.
2 Vascular Model
A 2D idealized coronary artery model was used for the purpose of flow analysis
using CFD techniques. Two adjacent stents of L stent 1 = 22 mm and L stent 2 = 12 mm
in length were inserted within the model, with a region with two overlapped struts
(Fig. 1). The main characteristics of both coronary model and stents were chosen
according to data extracted from the literature.
Details associated with the stent overlapping region are shown in Fig. 2.
The artery diameter D is considered to be 3 mm. The geometrical details associated
to the stents are: strut width w = 100 µm, strut height h = 100 µm and distance
between struts is Linterstrut = 1 mm.
A. Totorean et al.
Stent overlap is associated with impaired clinical and angiographic outcomes
at follow-up, regardless of stent type and overlap pattern. Stent thrombosis and
restenosis rates proved to be higher than in the case of single stent implantation
for both bare metal stents (BMS) and drug eluting stents (DES) and studies report
the following mechanisms as major determinants: incomplete or delayed endothelialization, incomplete strut coverage, increased vascular injury and inflammation,
or stent fracture. The impact of these phenomena translates clinically into increased
risk of repeat revascularization, myocardial infarction and even death [1, 2].
Wall Shear Stress (WSS) has been widely recognized as a key factor in both
atherogenesis and thrombosis processes [3]. Regions along the arteries walls associated with low WSS are prone to atherosclerotic plaque formation and neointimal
hyperplasia leading to in-stent restenosis, whereas high WSS seems to modulate
stent thrombosis [3–5].
Investigating the hemodynamic environment within a vascular segment is possible
using computational fluid dynamics (CFD) techniques. These methods permit the
analysis and description of near-wall flow patterns, WSS distribution, recirculation
zones, etc., for either native or stented coronary arteries [3–5].
Previous studies used CFD to investigate the hemodynamics associated with overlapping stents. These studies showed that the regions within the vessel exposed to the
overlapping segments are subjected to development of extended recirculation zones,
which associate increased size areas of low WSS, compared to the proximal or distal
parts of the stents not affected by overlap. These hemodynamic disturbances affect
drug distribution, concentration and drug wall uptake for drug eluting stents, delay
endothelial healing, promote platelet deposition and chronic inflammation regardless of stent type, and lead to increased risk for either stent thrombosis or in-stent
restenosis and lumen loss [6, 7].
The aim of this paper to investigate the near-wall flow behavior in case of
overlapping stents for an idealized 2D stented coronary model by analyzing and
describing the associated WSS distribution and recirculation zones, but also further
hemodynamic parameters like pressure distribution, using CFD.
2 Vascular Model
A 2D idealized coronary artery model was used for the purpose of flow analysis
using CFD techniques. Two adjacent stents of L stent 1 = 22 mm and L stent 2 = 12 mm
in length were inserted within the model, with a region with two overlapped struts
(Fig. 1). The main characteristics of both coronary model and stents were chosen
according to data extracted from the literature.
Details associated with the stent overlapping region are shown in Fig. 2.
The artery diameter D is considered to be 3 mm. The geometrical details associated
to the stents are: strut width w = 100 µm, strut height h = 100 µm and distance
between struts is Linterstrut = 1 mm.