Doctor Doctor

By: Lucinda Dargavel Date: 24/01/2018

Drum roll please... we have another Dr at PDR.

Research Officer Hanna, a member of PDR's Surgical and Prosthetic Design Team, recently completed her PhD which characterised the properties of coronary arteries that could be used to aid in the development of medical treatments for coronary artery disease. Below is a brief summary of her research. Congratulations Hanna!

The problem

Coronary heart disease (CHD) is the leading cause of mortality worldwide.

CHD is caused when coronary arteries (the arteries that supply oxygenated blood to the tissue of the heart) have restricted blood flow, associated with atherosclerosis – fatty material in blood forming plaque which builds up inside your arteries! If your heart tissue has a restricted blood flow, the tissue can die which could result in a heart attack, and blood will no longer be pumped effectively to the other parts of your body.

There are various options for treatment of CHD. Coronary angioplasty inflates a little balloon at the blockage to open the artery, and a stent (a metallic wire tube) may be inserted to hold the artery open once the balloon is removed. Alternatively, a coronary artery bypass graft may be performed. This requires a donor blood vessel to create a ‘diversion’ around the blocked artery. Treatment of CHD is not always successful, and complications such as restenosis (arteries closing again), or thrombosis (blood clots) can occur.

2D SEM images of coronary artery at (a) 100x, (b) 1000x and (c) 2000x magnification

The research

The aim of the research was to characterise properties of coronary arteries that could be used to aid in the development of medical treatments for coronary artery disease.

This aim was met by measuring the viscoelastic (mechanical) and surface roughness properties coronary arteries:

·      The surface roughness of coronary arteries was quantitatively characterised. Further, surface roughness was investigated at increased magnification in a multi-scale study. A correction factor was presented for changes in surface roughness due to chemical processing of tissue.
·      The dynamic viscoelastic properties of coronary arteries were measured at physiological relevant frequencies.
·      The effect of damage inflicted on coronary artery specimens through chemical fixation and dehydration, and mechanical overloading, was assessed through the change in surface roughness.

2D AFM image of coronary artery

The significance

It is important to consider the physiological loading conditions of biomaterials that are designed to replicate coronary arteries, as storage modulus was noted as frequency-dependent (as your heart beats faster/slower, the mechanical properties change).

Damage can be caused by stretching the artery, as if it were under increased loading conditions, which results in a change in surface roughness. Chemical processing, specifically dehydration, also resulted in a change in surface roughness. Surface roughness affects blood flow, which can influence blood clot formation.

The mechanical and surface roughness properties of coronary arteries, measured in this study, can be applied to device design, disease assessment and computational modelling.