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Michel Labrosse interview: New framework helps cardiac surgeons plan aortic and mitral valve repair procedures

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Michel Labrosse Ph.D., P.Eng

 

Michel Labrosse Ph.D., P.Eng. is the Vice-Dean (Interim), Graduate Studies, and Associate Professor, Department of Mechanical Engineering, University of Ottawa, Canada.  His team utilizes ViVitro Labs equipment in their research and cites it in research publications.  Rob Fraser, Lab Manager at ViVitro Labs, recently spoke with Dr. Labrosse to learn more.

A native from France, Professor Labrosse received his Diplôme d’Ingénieur from the École Centrale de Nantes in 1993, with a specialization in structural engineering. He obtained a Ph.D. in Mechanical Engineering from the same institution in 1998, and pursued his research work on the finite element modelling of wire ropes and cord-rubber materials during a post-doc at the University of Akron, Ohio, in the United States.

Labrosse then spent 5.5 years with the Heineman Medical Research Laboratory at the Carolinas Medical Center in Charlotte, North Carolina, working on various problems in cardiovascular mechanics related to clinical topics.

Professor Labrosse joined the Department of Mechanical Engineering at the University of Ottawa in 2005. His research interests revolve around theoretical and computational structural analysis and its applications to the diagnosis and surgical treatment of cardiovascular diseases.

Rob Fraser:  Please tell us about your current work:

Professor Labrosse:   I collaborate with several clinicians at the University of Ottawa Heart Institute.  The objective of my lab is to improve basic science in cardiovascular mechanics.  For example, the description and understanding of soft tissue mechanics, cardiac valve geometry and function, as well as cell mechano-biology.  We’d like to combine this knowledge with the development of new computational tools for use by the medical community.  For instance we are developing a framework to help cardiac surgeons with the planning of repair procedures on the aortic and mitral valves.  That’s basically the bulk of what we are doing right now, and it goes in so many directions.

We need to develop our own tools—for instance, to process medical imaging data.  We’re also developing a new shell finite element specific to soft tissues and dynamics.  But the clinical input is very important for us to stay relevant.    We want our simulations to be as clinically meaningful as possible, and this forces us to carry out experiments as well, to validate our simulations.  For example, we’ve run lots of experiments on the human aorta and on the aortic valve.  We test the aortic valve in the ViVitro system.    We want to see if what we see in the machine is comparable to what we are able to simulate in our finite element models.

Rob Fraser: How is the work going?

Professor Labrosse: We’re pushing the limits.  We’ve been able to develop tools to use images from 3D ultrasound.  We can now build finite element models of parts that actually are in patients or subjects.  We want to reproduce their function as faithfully as possible.  The geometries you see in vivo are pressurized, but if you are interested in stress and strain computations, you actually need to start from the unpressurized geometries. This comes with many technical challenges that we’ve recently started to overcome.

We’ve been successful in normal human valves, now we’re moving to diseased human valves and it’s another ballgame altogether because the material properties are potentially very different from the normal ones and they are difficult to figure out.

At the same time, with my clinician colleagues, we are interested in modelling the different procedures that are used to repair aortic valves.  We can do that on a computer relatively easily, but we also need to get input from experimental work.  Again, it’s done in the ViVitro system.   For example, a cardiac resident runs a pig valve where a leaflet has been removed; we look at the AI, and then fix the leaflet according to different surgically relevant techniques, and we finally test how the valve is performing.  From the ViVitro machine, we get information about cardiac output, leaflet dynamics, left ventricular work,  speed of opening and closing of the leaflets, maximum effective orifice area—things like that.  And from our simulations, we can get access to stress levels in the leaflets, etc.  Of course, we check if the simulations are telling similar things to what we see in the experiments.

Rob Fraser:  What are the reactions to this work?

Professor Labrosse:  The clinicians are keen.  They want the simulations done yesterday.  Because we are getting there for the aortic valve, now we have to move toward the same things in the mitral valve.  And the ViVitro machine should be able to help us there as well.

Rob Fraser:  What are your plans for the future?

Professor Labrosse: We are pushing hard toward the modelling of the diseased aortic valves, whether they are dilated by an aneurysm or bicuspid valves.  We want to simulate them properly and give advice to surgeons as to what procedures should work best for removing the AI.   That’s a big goal we have.  We are also planning to do similar work on the mitral valve. Our expectations from experiments have been growing, so now, we’re also very interested in an ex-vivo model to get better images. Right now, the ViVitro is working just fine for us, but when we try to image the valves that are running on the machine using the usual clinical imaging methods like 3D transesophageal echography, we don’t see the valves so well because there is interference with plastic objects and things like that.   We’re really hoping that we can get better imaging from an ex vivo model, so that we could process the data in a completely similar way to what we do with human data.  We have data coming from humans and we can simulate things from them.  To close the loop, we’d like to have the same type of data coming from the lab as well so that we can control conditions much better and try out surgical things that wouldn’t be done on humans yet.

Rob Fraser:  What has been the most exciting moment in your career to date?

Professor Labrosse:  When I learned it was possible to extract data out of medical imaging machines.  For years I had been getting information by making measurements off of monitors on heart valves. All of a sudden, in 2010, I could get access to the raw data when Philips opened up its equipment to the research community. The heavy work started there as well.  I needed to create my own way of processing the data towards the goals I had.  It has panned out beautifully, but it’s only the beginning.  There’s so much more we can do with the data.  It’s been super-exciting.

Rob Fraser:  How has ViVitro helped in your work?

Professor Labrosse:  It really is like an industry standard.  I love the machine. The first time I saw the machine in action was at the Heineman Medical Research Laboratory in Charlotte where I was working with Dr. Mano Thubrikar—a pioneer in aortic valve research. I saw there that it was a fantastic machine.  When I became an associate professor at U of Ottawa in 2005, the first thing I did was write a proposal to try and get that machine.  I was lucky enough to get it in 2006.  It’s really a fundamental tool for validation of whatever I’m doing in terms of simulation.  That’s big.

Rob Fraser:  Do you have advice for our readers in cardiovascular research working with clinicians?

Professor Labrosse: It’s very challenging, but you want to stick to what’s clinically relevant.  Automatically, you will end up with beautiful, fundamental questions from that.  If you don’t have the clinician teams excited about what you’re doing, they will lose interest and the collaboration will fizzle out fairly rapidly.  It’s a win-win situation when you are trying to solve something that’s useful for the clinicians.  Unfortunately for them, it takes a lot more time to solve than what they would like. But that’s the way research is.

Rob Fraser:  How do you help set the expectation that this will take time?

Professor Labrosse:  That’s a challenge but clinicians know they too can’t always get what they want.  They are very busy in the clinic and they have night calls and things like that.  They realize I may have limiting factors as well because of the admin work and the teaching I am doing and so on.  We’re all just humans!  It’s a bitter pill to swallow for everyone, so at the end of the day, we need to work with reasonable people.

Read more interviews with Cardiovascular Pioneers.