Concordia Researchers Develop New Method for Evaluating the Health of Artificial Heart Valves



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Researchers at Concordia have developed a technique to detect obstructions in a type of mechanical heart valve that they believe will contribute to safer monitoring methods for cardiologists and their patients.

The team led by Lyes Kadem, a professor in the Department of Mechanical, Industrial and Aerospace Engineering at the School of Engineering and Computer Science Gina Cody, published his findings in the journal Artificial Organs. PhD candidate Ahmed Darwish was the lead author, and Giuseppe Di Labbio, assistant professor Wael Saleh and Othman Smadi of Hashemite University in Jordan contributed.

The researchers used high-tech equipment to analyze the downstream flow of a two-leaf mechanical heart valve (BMHV). The equipment included a dual-activated custom-designed left heart duplicator designed and created in his laboratory by Concordia undergraduates, a high-speed camera and a laser.

Despite its impressive name, the BMHV is a simple ring with an inside diameter of about 2.5 cm. Two carbon-based leaflets inside the ring open and close while the heart pumps blood out of the left ventricle and into the aortic arch, which sends blood to the body.

They replace damaged aortic valves and are installed via open heart surgery. A blocked BMHV can be catastrophic.

Mapping of blood flow

The team's method maps the blood flow patterns that result from six different heart valve blocks. The researchers photographed particles immersed in a fluid that mimicked the blood and pumped fluid through the heart duplicator.

Using a technique called particle image velocimetry, they were able to determine the velocity of the flow. It allowed them to simulate the blood flow with the leaflets completely free of obstruction, when they were partially obstructed and when completely clogged.

"Imagine you're out of a stadium and the crowd is coming out of three gates side by side," says Kadem, president of Concordia Research for Cardiovascular Engineering and Medical Devices.

"If the gates are open, you'll see a uniform distribution of people coming out of all three openings. If a gate is closed, you will see more people coming out of the other two and none of which is closed. Therefore, you will deduce that there is a blockage. "

When applied using magnetic resonance phase contrast (MRI), the method is both non-invasive and radiation free, says Kadem. This means that doctors can use it to detect and monitor BMHV dysfunction.

"Today, ultrasound is the best way to detect valve dysfunction," he says. "The next step is cinefluoroscopy, which uses radiation. You can not use this method as an accompaniment because it exposes the patient to radiation and increases the risk of cancer. "

Darwish and Kadem note that artificial heart valves are generally safe but are not risk free. There are between 0.1% and 6% chance of dysfunctions that can occur between one hour and 20 years after the replacement of the organic valve. These can be fatal, with a mortality rate of 28.6% 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 article: Experimental investigation of the downstream flow of a mechanical dysfunctional double leaflet aortic valve.

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