Elsevier

Journal of Biomechanics

Volume 47, Issue 2, 22 January 2014, Pages 505-511
Journal of Biomechanics

Hemodynamics in coronary arteries with overlapping stents

https://doi.org/10.1016/j.jbiomech.2013.10.048Get rights and content

Abstract

Coronary artery stenosis is commonly treated by stent placement via percutaneous intervention, at times requiring multiple stents that may overlap. Stent overlap is associated with increased risk of adverse clinical outcome. While changes in local blood flow are suspected to play a role therein, hemodynamics in arteries with overlapping stents remain poorly understood. In this study we analyzed six cases of partially overlapping stents, placed ex vivo in porcine left coronary arteries and compared them to five cases with two non-overlapping stents. The stented vessel geometries were obtained by micro-computed tomography of corrosion casts. Flow and shear stress distribution were calculated using computational fluid dynamics. We observed a significant increase in the relative area exposed to low wall shear stress (WSS<0.5 Pa) in the overlapping stent segments compared both to areas without overlap in the same samples, as well as to non-overlapping stents. We further observed that the configuration of the overlapping stent struts relative to each other influenced the size of the low WSS area: positioning of the struts in the same axial location led to larger areas of low WSS compared to alternating struts. Our results indicate that the overlap geometry is by itself sufficient to cause unfavorable flow conditions that may worsen clinical outcome. While stent overlap cannot always be avoided, improved deployment strategies or stent designs could reduce the low WSS burden.

Introduction

About 30% of patients undergoing percutaneous coronary intervention (PCI) with stent placement are treated with overlapping stents (Holmes et al., 2004, Räber et al., 2010). Stent overlap is associated with increased risk of adverse clinical outcome for both bare metal stents (BMS) and drug eluting stents (DES) (Ellis et al., 1992, Räber et al., 2010). Various studies have investigated clinical results and biological aspects of stent overlap, but the hemodynamics inside arteries with overlapping stents and the associated wall shear stress (WSS) parameters have received much less attention (Balakrishnan et al., 2005, Charonko et al., 2010, Peacock et al., 1995). This can be in part attributed to the lack of suitable methods for acquiring the geometry of arteries containing overlapping stents with sufficient accuracy.

Stent overlap is associated with increased in-stent restenosis and lumen loss due to delayed healing and increased inflammation regardless of stent type (Räber et al., 2010, Wang et al., 2000). While DES may reduce neointimal hyperplasia and restenosis in single stent cases (Moses et al., 2003, Tsagalou et al., 2005), their performance (Finn et al., 2005, Matsumoto et al., 2007) and safety (Moreno et al., 2005) in regions of overlap are a case of debate. Overlapping BMS are associated with worse clinical outcome compared to single BMS (Kastrati et al., 1999, Kereiakes et al., 2006, Serruys et al., 2002). This is attributed primarily to more pronounced arterial injury caused by the expansion of two stents at the same location, leading to increased inflammation. However, the poorer outcome may also be related to severe hemodynamic disturbances introduced by stent malapposition (Charonko et al., 2010) that are inherent in stent overlap but occur infrequently in single stents (Matsumoto et al., 2007).

It is generally accepted that hemodynamics influences vascular health and pathogenesis. WSS as one of the manifestations of blood flow has been shown to be an important factor in atherogenesis (Chatzizisis et al., 2007, Cheng et al., 2006) and in the pathobiology of neointimal hyperplasia, thrombosis and in-stent restenosis (Papafaklis et al., 2010, Wentzel et al., 2008). These latter processes are a concern in percutaneous vascular intervention in general and in stent placement in particular. For example, stent malapposition has been shown to increase thrombogenicity. It is hypothesized that hemodynamics plays a role therein, as adjacent high shear stress areas and recirculation zones caused by malapposed stents may activate platelets and increase local residence times of these thrombocytes (Hathcock, 2006, Kolandaivelu et al., 2011, Peacock et al., 1995). Kolandaivelu and co-workers showed in vitro and in a 2D computational model with idealized domain geometry that flow recirculation between malapposed and overlapping stent struts may modulate stent thrombogenicity (Kolandaivelu et al., 2011).

Computational fluid dynamics (CFD) is the method of choice for assessing shear stress and local hemodynamics in stented arteries. The precise acquisition of the stent struts and arterial geometry is a prerequisite for accurate CFD analysis, but no clinical imaging modality exists that could yield such data with sufficient resolution. Several approaches have been reported in the literature to circumvent this limitation: simulations may be conducted on idealized geometries based on stent CAD data (Gundert et al., 2011), on hybrid domains where the stent free geometry is obtained by CT, digital angiography or MRI and a stent is virtually implanted (De Santis et al., 2010, LaDisa et al., 2006), on ex vivo micro-computed tomography (µCT) data of explanted, stented arteries (Morlacchi et al., 2011) or µCT images of stented in vitro artery models (Benndorf et al., 2009, Connolley et al., 2007). While these methods have their undisputed respective strengths, they have either limited geometric accuracy, limited treatable vascular domain size or incomplete representation of the mechanical interaction between stent and arterial wall.

We have recently introduced a method that allows for precise ex vivo acquisition of arteries stented in vivo or ex vivo, yielding both the macroscopic arterial tree geometry as well as the configuration and morphology of individual stent struts (Rikhtegar et al., 2013). Here we make use of this method to investigate the shear stress distribution and hemodynamics of porcine coronary arteries with overlapping stents. Our goal is to evaluate flow disturbances and consequent shear stress alterations introduced by stent overlap which may contribute to the reported clinical problems associated with overlapping stents.

Section snippets

Methods

A concise description of the utilized methods is given here. We refer the reader to the Supplemental material and Rikhtegar et al. (2013) for a more detailed explanation of the individual process steps.

Results

It has been shown previously that the acquisition method used here can capture single stented arteries accurately at high resolution (Rikhtegar et al., 2013). Fig. 1 illustrates that this method also ensures anatomic fidelity in the case of overlapping stents, showing that it captures regions of prolapse between stent struts (Panel A), axial arterial deformation caused by the stent implantation (Panel B), strut overlap and relative positioning (Panel C), radial arterial deformation (Panel D)

Discussion

It is known that hemodynamics influences atherogenesis (Chatzizisis et al., 2007, Samady et al., 2011), thrombogenesis (Hathcock, 2006), vascular remodeling (Stone et al., 2003), neointimal hyperplasia (Wentzel et al., 2001) and endothelial healing (Franco et al., 2013). It is further known that stent overlap, compared to single stents, increases thrombogenicity (Kolandaivelu et al., 2011, Rogers and Edelman, 1995), may delay the re-endothelization and enhance platelet deposition and thrombus

Conclusion

We have shown that the relative size of low WSS areas is increased significantly in regions of stent overlap compared to non-overlapped regions. Since low WSS is generally accepted as a factor in atherogenesis and thrombogenesis, we conclude that the adverse hemodynamics caused by stent overlap may be responsible in part for the adverse clinical outcome in patients that are treated with overlapping stents. In cases where stent overlap cannot be avoided, new deployment strategies or stent

Conflict of interest statement

We have no conflicts of interest to report.

Acknowledgments

We thank Ryan J. Choo and Gian N. Schädli of ETH Zurich for help with the micro-computed tomography and image segmentation, respectively. This work was partially funded by the Swiss Federal Commission for Technology and Innovation through EnOp, grant 9921.1, and the Swiss National Science Foundation through NCCR Kidney.CH.

References (54)

  • R. Moreno et al.

    Drug-eluting stent thrombosis – results from a pooled analysis including 10 randomized studies

    J. Am. Coll. Cardiol.

    (2005)
  • U. Olgac et al.

    Computed high concentrations of low-density lipoprotein correlate with plaque locations in human coronary arteries

    J. Biomech.

    (2011)
  • J. Pache et al.

    Intracoronary stenting and angiographic results: strut thickness effect on restenosis outcome (ISAR-STEREO-2) trial

    J. Am. Coll. Cardiol.

    (2003)
  • M.I. Papafaklis et al.

    The effect of shear stress on neointimal response following sirolimus- and paclitaxel-eluting stent implantation compared with bare-metal stents in humans

    J. Am. Coll. Cardiol. Cardiovasc. Interv.

    (2010)
  • J. Peacock et al.

    Flow instabilities induced by coronary artery stents: assessment with an in vitro pulse duplicator

    J. Biomech.

    (1995)
  • L. Räber et al.

    Impact of stent overlap on angiographic and long-term clinical outcome in patients undergoing drug-eluting stent implantation

    J. Am. Coll. Cardiol.

    (2010)
  • F. Rikhtegar et al.

    Choosing the optimal wall shear parameter for the prediction of plaque location—a patient-specific computational study in human left coronary arteries

    Atherosclerosis

    (2012)
  • P.W. Serruys et al.

    A randomized comparison of the value of additional stenting after optimal balloon angioplasty for long coronary lesions: final results of the additional value of NIR stents for treatment of long coronary lesions (ADVANCE) study

    J. Am. Coll. Cardiol.

    (2002)
  • E. Tsagalou et al.

    Multiple overlapping drug-eluting stents to treat diffuse disease of the left anterior descending coronary artery

    J. Am. Coll. Cardiol.

    (2005)
  • A.G. van der Giessen et al.

    The influence of boundary conditions on wall shear stress distribution in patients specific coronary trees

    J. Biomech.

    (2011)
  • R.-J. van Geuns et al.

    Self-expanding versus balloon-expandable stents in acute myocardial infarction: results from the APPOSITION II study: self-expanding stents in ST-segment elevation myocardial infarction

    J. Am. Coll. Cardiol. Cardiovasc. Interv.

    (2012)
  • D.R. Wells et al.

    Effect of carotid artery geometry on the magnitude and distribution of wall shear stress gradients

    J. Vasc. Surg.

    (1996)
  • B. Balakrishnan et al.

    Strut position, blood flow, and drug deposition: implications for single and overlapping drug-eluting stents

    Circulation

    (2005)
  • G. Benndorf et al.

    Wall shear stress in intracranial self-expanding stents studied using ultra-high-resolution 3D reconstructions

    Am. J. Neuroradiol.

    (2009)
  • R.M. Berne et al.

    Cardiovascular Physiology

    (1986)
  • J. Charonko et al.

    In vitro comparison of the effect of stent configuration on wall shear stress using time-resolved particle image velocimetry

    Ann. Biomed. Eng.

    (2010)
  • H.Y. Chen et al.

    Mis-sizing of stent promotes intimal hyperplasia: impact of endothelial shear and intramural stress

    Am. J. Physiol. Heart Circ. Physiol.

    (2011)
  • Cited by (51)

    • Superficial femoral artery stenting: Impact of stent design and overlapping on the local hemodynamics

      2022, Computers in Biology and Medicine
      Citation Excerpt :

      The findings of the work showed that the presence of stent overlapping provokes an abrupt alteration in the WSS-based descriptors. In particular, lower median values of TAWSS were found at the overlapping region, in agreement with previous investigations on overlapped coronary stents [29–31]. Moreover, the overlapping region exhibited lower median values of transWSS, and higher median values of OSI and WSSRATIO than the stented regions upstream and downstream from the overlapping.

    • Is stent Overlap Still an Achilles' Heel of Drug-Eluting Stents?

      2020, Cardiovascular Revascularization Medicine
    • Comparison of Morphological Patterns Between In-Stent Restenosis Lesions of Overlapping and Non-Overlapping Second- and Third-Generation Stents Using Optical Frequency Domain Imaging

      2020, Cardiovascular Revascularization Medicine
      Citation Excerpt :

      The hemodynamic effect of overlap is dependent on overlapping strut configuration and stent structural characteristics. The vessel wall area in the overlapped segments is exposed to an overall lower shear stress compared with the adjacent areas covered by a single stent [14]. In particular, low wall shear stress has been identified as an important factor impacting atherogenesis, neointimal growth, ISR, and stent thrombosis [15–17].

    • Numerical simulation of magnetic nanoparticle-based drug delivery in presence of atherosclerotic plaques and under the effects of magnetic field

      2020, Powder Technology
      Citation Excerpt :

      Applications of these materials include increasing the quality of the image in Magnetic Resonance Imaging (MRI), drug delivery to cancerous tissues, hyperthermia, and manipulating cell membranes. With the help of Drug-Eluting Stents (DESs), MNPs have recently been used for treating restenosis in the artery [1,10,11]. The effect of particle size, blood flow velocity, magnetic field strength, and injection time on the distribution of MNPs concentration were numerically studied in some recently published papers [12–14].

    • Feasibility of Implanting 50–60 mm-Tapered Drug Eluting Stents in Chronic Total Occlusions

      2019, Cardiovascular Revascularization Medicine
      Citation Excerpt :

      This increased risk could be explained by local hypersensitivity reaction to a specific polymer or drug [18], persistent inflammation [19], stent thrombosis and in-stent restenosis because of increased arterial injury, poor endothelization, and delayed healing [18–20]. In addition, the overlap geometry has been described to cause, by itself, unfavorable flow conditions that may worsen clinical outcome [21]. Moreover, the use of several overlapped segments leads to engagement of secondary branches due to the presence of a physical double layer of stent struts [22].

    View all citing articles on Scopus
    View full text