Engineering medical advances
This article is part of a special issue from the Concordia Journal entitled: "The heart -- it beats, it pumps, it bleeds, it leaps -- it knows what it wants".
As an engineering undergraduate, Lyes Kadem was not sure he wanted to pursue research in biomechanics. Seeing the beneficiaries of his research at the children’s hospital in Quebec City during a recent meeting with two cardiologists, he was reminded why he made his choice.
“It’s encouraging to look around and recognize that you’re doing something really useful.”
Kadem joined Concordia's faculty in Mechanical and Industrial Engineering four years ago and now runs the Laboratory of Cardiovascular Fluid Dynamics (LCFD) where graduate and undergraduate students can test possible solutions to common problems in heart health and function. It’s clear that he sees medical problems in mechanical terms.
Picking up a small plaster model in the lab (one he jokingly adds, his students refer to as his ‘Dollarama heart’) he uses it to illustrate the heart’s ideal function and potential blockages.
“The left side of the heart handles 10 times more pressure than the right side,” he explains, pointing at the model. “The valve leading to the aorta is like an exhaust valve in an internal combustion engine and the ventricle plays the role of the piston working up and down.”
Mixing his disciplinary metaphors is actually at the heart (ahem) of Kadem’s research. “A lot of the problems they are identifying in medicine actually are classical problems in fluid mechanics.” Researchers in the LCFD are applying the solutions to cardiovascular complications with the heart as ‘internal combustion engine’ runs less efficiently due to congenital factors, age or diet.
The valve that allows oxygenated blood to flow through the aorta is trileaflet (having three flaps that open and close in unison) and can be damaged by congenital, dietary or agerelated causes. Replacement valves have to be non thrombogenic (unlikely to contribute to blood clots) and long-lasting. Given that there are currently a quarter million heart valve replacements required annually around the world, the mechanism also must be reliable, and easily produced.
Currently, replacement heart valves tend to be trileaflet, if biologically adapted (with parts from other animals) or bileaflet, if mechanically developed. The two options have pros and cons in terms of longevity, adaptability and purpose. The research projects in the LCFD focus on improving options in replacement technology, and increasing information about when and how that type of surgery yields the best, long-term results.
The room in the sub-basement of the EV Building has two different Doppler echocardiographic machines to record the function of the various mechanical simulators. Some of the simulators use different experimental heart valve technologies, others modify the heart’s function in other ways. “If we are going to determine the parameters of heart function effectively, we need to use the same tools as doctors,” explains Kadem.
Meanwhile, he is working with a team of students testing prosthetic heart valves introduced in a procedure less than a decade ago. So far, results of the new process are promising, but the system is still too new to gauge long-term performance. The students have created a simulated heart using the system that beats 60 times the normal rate of about 70 beats a minute. In other words, the machine compresses a minute of normal use into one second, vastly speeding up the process. The team can extrapolate how recently introduced treatment innovations, involving materials used to construct artificial valves, will react to extended wear and tear. Potential long-term problems can be identified before they are experienced by patients who have undergone the procedures.
Kadem has supervised teams of students addressing some questions raised by biomechanical heart interventions as part of their final capstone projects (engineering students in all disciplines work together to complete a year-long project as final ‘cap’ on their degree requirements.) Two years in a row, teams working in his lab have won the award for the best mechanical project.
One capstone team developed a mechanical trileaflet valve. Another award-winning team analysed a weak aspect of the aortic structure that can lead to fatality in highimpact situations like car crashes. Design of an experimental setup for the evaluation of blunt traumatic aortic rupture sends an elastic model of the heart on a trolley along a track the length of the lab, barrelling towards a shock absorber. Photos record the specifics of the impact, allowing for improved airbag or seatbelt design.
This year’s team is working on the simulation project speeding up the rate of a mechanical heart to determine what potential weaknesses may become apparent with prolonged use of the valve structure introduced a decade ago.
This article is part of a special Heart issue from the Concordia Journal, which includes these other stories:
• PERFORM Centre on track
• Engineering researcher develops touching technology
• Athlete moves to exercise science
• Intensive exercise science course challenges graduate students
• Concordia ♥ Michael Di Grappa
• Write now: Putting her heart on the shelf
Related links:
• Graduate program in Mechanical and Industrial Engineering
• Capstone projects site in the Faculty of Engineering and Computer Science