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Researchers at Concordia have devised a technique to detect obstructions in a type of mechanical heart valve they believe will contribute to safer follow-up methods for cardiologists and their patients.
The team led by Lyes Kadem, Professor in the Department of Mechanical, Industrial and Aerospace Engineering at the Gina Cody School of Engineering and Computer Science, published their findings in the journal Artificial Organs. PhD candidate Ahmed Darwish was lead author, and Giuseppe Di Labbio, badistant professor Wael Saleh and Othman Smadi of Hashemite University in Jordan contributed.
The researchers used high-tech equipment to look at the flow of a bi-leaflet mechanical heart valve (BMHV). The equipment included a custom-made dual-activation left-brain duplicator designed and created in their lab by Concordia undergraduate students, a high-speed camera and a laser.
Despite the impressive name, the BMHV is a simple ring with an inner diameter of about 2.5 cm. Two carbon-based leaflets inside the ring and close to the heart pumps blood out of the left ventricle and into the aortic arch, which sends the blood out into the body.
They replace damaged valves, and are installed via open-heart surgery. An obstructed BMHV can be catastrophic.
Blood flow mapping
The method the team designed maps simulated blood flow patterns that result from six different heart valve blockages. The researchers photographed particles immersed in a fluid that mimics blood and pumped the fluid through the heart duplicator.
Using a technique called particle image velocimetry, they were able to determine the flow velocity. It was obvious that they would be completely obstructed when fully obstructed.
"Kadem, the Concordia Research Chair for Cardiovascular Engineering and Medical Devices, says:" Imagine you're outside of the stadium and the crowd.
"If the gates are open, you will see a uniform distribution of people leaving all three openings. If one gate is closed, you will see more people leaving the others, and no one is closed. Therefore, you will be sure that there is a blockage. "
When applied using phase-contrast magnetic resonance imaging (MRI), the method is both non-invasive and radiation-free, says Kadem. That means doctors can use it for BMHV dysfunction detection and follow-up.
"Currently, ultrasound is the best way to detect valve dysfunction," he says. "The next step is cinefluoroscopy, which uses radiation. You can use this method as a follow-up because it exposes the patient to radiation and increases their risk of cancer. "
Darwish and Kadem notes that artificial heart valves are generally safe but not risk-free. There is between 0.1 per cent and 6 per cent chance of dysfunction that can occur between one and two years after they replace the organic valve. These can be fatal, with a 28.6 percent mortality rate when a dysfunction results in an emergency.
This research is supported by a grant from the Natural Sciences and Engineering Research Council of Canada.
Read the cited paper: Experimental investigation of the flow of a dysfunctional bileaflet mechanical aortic valve.
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