Pujith Vijayaratnam LinkedIn
Research Associate, University of New South Wales, Australia.
"Computational and experimental investigation of myocardial bridging"
"Alleviating the adverse haemodynamics of arteries treated with drug-eluting stents without compromising drug uptake"
Research interests: CFD, blood flow, laser-induced fluorescence, drug-eluting stents, myocardial bridging
Current project: Myocardial bridging
One of our main areas of research is to investigate the mechanism of myocardial bridging, a congenital condition that is of interest to our partners at Concord Hospital. This condition occurs when part of a coronary artery is embedded within the heart muscle. The rhythmic squeezing of the artery by the surrounding heart muscle can result in the periodic narrowing of the artery during each cardiac cycle. Although this condition is usually benign, its presence has been linked to ischemic chest pain, depressed ventricular function, arrythmia and sudden death. In my research, an experimental model is being developed to study the fluid dynamics associated with this condition. It is hoped that the data obtained can be used to validate computational models and to help explain how the fluid dynamics associated with myocardial bridging can give rise to the aforementioned diseases. It is also hoped that the results can be used to assist in clinical decision making.
PhD: Drug eluting stents
Drug-eluting stents are small, metallic, wire-mesh tubes that are implanted into occluded arteries that have been restored to their original patency through the expansion of a balloon catheter. The stent acts as a mechanical scaffold that minimises the risk of arterial collapse, whilst a drug coating on the stent surfaces reduces smooth muscle cell proliferation at the arterial injury sites. However, in-stent restenosis – defined as the reduction in diameter of a stented vessel by more than 50% - persists in up to 20% of drug-eluting stent patients. Furthermore, blood clots persist in up to 0.8% of patients after more than 30 days have passed since stent implantation. This condition, known as late stent thrombosis, is associated with a 45% mortality rate.
The primary aim of my thesis was to use computational fluid dynamics simulations to identify methods of attenuating the stent-induced haemodynamic disturbances that give rise to these diseases, without compromising drug transport into the arterial tissue. The haemodynamic and drug transport behaviour of stented arteries were also characterised in these simulations and the drug transport behaviour was validated using in-vitro experiments. The results obtained showed that the non-Newtonian properties of blood, its complex near-wall behaviour, and the pulsatility of its flow each have minimal impact on the drug transport behaviour from stents into arterial tissue. This was found to be because the surfaces of the stents that are exposed to arterial blood flow are much more rapidly depleted of drug than the surfaces that directly contact arterial tissue. We also found that the drug that is transported from these non-contacting surfaces is not significantly taken up by the arterial tissue but is instead lost to the surrounding blood flow. Hence, the overall drug uptake is driven primarily by this direct contact whilst flow-mediated drug transport is negligible.
It was therefore concluded that drug transport can be enhanced in stented arteries by extending the region of contact between the drug coating and the arterial tissue. We also showed that this extended contact region can be used in conjunction with streamlined stent strut geometries to alleviate the adverse haemodynamics of stented vessels without compromising drug uptake.
2017-present Research Associate, UNSW, Sydney
2013-2017 PhD Mechanical Engineering (CFD), UNSW, Sydney
2009-2012 BEng Honours Class 1 (Mechanical Engineering), UNSW, Sydney
Vijayaratnam, P.R., O’Brien, C.C., Reizes, J.A., Barber, T.J. and Edelman, E.R., 2015. The impact of blood rheology on drug transport in stented arteries: Steady simulations. PloS one, 10(6), p.e0128178.
Paterson, S., Vijayaratnam, P., Perera, C. and Doig, G., 2016. Design and development of the Sunswift eVe solar vehicle: a record-breaking electric car. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 230(14), pp.1972-1986.
Vijayaratnam, P.R.S., Barber, T.J. and Reizes, J.A., 2017. The Localized Hemodynamics of Drug-Eluting Stents Are Not Improved by the Presence of Magnetic Struts. Journal of biomechanical engineering, 139(1), p.014502.
Vijayaratnam, P.R.S., Barber, T.J. and Reizes, J.A., 2014, January. Using Magnetic Struts to Alleviate Adverse Haemodynamic Flow Effects around Drug-Eluting Stents. In Cardiology (Vol. 128, pp. 340-340). Allschwilerstrasse 10, Ch-4009 Basel, Switzerland: Karger.