Dr. Janarthanan Sathananthan

Dr. Janarthanan Sathananthan on Impact of Transcatheter Heart Valve Overexpansion


Dr. Janarthanan Sathananthan and Rob Fraser

Dr. Janarthanan Sathananthan and Rob Fraser

The TVT moderated poster sessions on June 21st, in Chicago Illinois featured Janarthanan Sathananthan, MBChB, MPH, lecturing on the Overexpansion of the SAPIEN 3 Transcatheter Heart Valve: An Ex-vivo Bench. Dr. Janarthanan Sathananthan (JS) is an international fellow working at the Centre for Heart Valve Innovation (CHVI) based at St Paul’s Hospital (Vancouver BC) and led by Dr John Webb and Dr David Wood. He recently visited ViVitro Labs and spoke with General Manager, Rob Fraser (RF) about his work.

JS: The work that I do on a day to day basis is clinical. We look after patients, we perform procedures. Part of the research work that I’ve been involved with at the CHVI has been bench testing of valves. The CHVI has established a reputation for performing pioneering work in transcatheter valves, which includes a strong track record of first in man implantations. A number of techniques in the area of transcatheter devices have been developed at the CHVI. The work specific to the poster that we presented last week has been looking at the SAPIEN S3 valve and seeing whether it could be over-expanded beyond its labelled diameter.

The clinical context is that there are currently four available sizes, but patients may not neatly fit these four available sizes. The company recommends valve deployment to recommended guidelines to avoid any potential compromise to performance and function of the valve. The information gap is: what happens to these valves when you make them bigger than their labelled diameter? Clinicians have been doing this in real world practice to deal with this conundrum of patients not quite fitting the size range.

We took three commonly commercially available valves of three different sizes – the 23, 26 and 29mm S3. We then incrementally over expanded them by a millimeter at a time, up to 3 millimeters bigger then their labelled diameter. We found that overexpansion, both modest and aggressive, is possible. Also there is a graduated response in terms of hydrodynamic function and leaflet restriction related to the size of the THV. Overall I think the work has provided a lot of insights to clinicians on what the effect of doing this is to the valve itself. There is still a lot more work to be done, but I think this is a nice initial stepping stone.

RF: The key thing there is the acute factor which we were looking for and we haven’t gotten into durability yet with expansion.

JS: Correct. And one of the challenges that I kind of alluded to earlier is that there really needs to be a partnership between industry and physicians to look at these kinds of off label uses of devices because it’s already happening in the community clinically. Physicians have adopted to meet clinical challenges and certainly more work like this is needed. There are challenges with getting the valves and the equipment required to do this kind of important testing.

RF: You mentioned during a conversation we had in the lab that you were doing things on people before you’ve ever seen them on the bench.

JS: I think there is certainly an element of that. We work very closely with industry and they are integral when new systems or techniques are introduced. There’s always been a strong partnership, but sometimes there is a real need for investigator driven work. I think that’s really important for clinicians scientists, and most importantly, patients.  The need for more bench work is important. I think there’s been a recognition of that and there is a lot of interest and a lot of different ways to address this problem. There are some centres that are using computer modelling, virtual reality and all kinds of interesting and novel techniques to try and simulate things before they’re performed on patients.

Our interest at the moment at CHVI has been bench testing because we think that provides a lot of very useful insights which influences how we care for patients.

RF: How has ViVitro helped in your bench testing?

JS: ViVitro has been really integral in our project that we presented last week and has been accepted for publication. It continues to be extremely important going forward as we undertake some further bench projects. It’s been a really nice partnership between us at CHVI and ViVitro. We’ve been able to undertake some very important hydrodynamic testing using the pulse duplicator that’s commercially available. It’s really added a lot of scientific rigor to our scientific question. For example, in the case of our over expanded valves we’ve been able to test this as how industry would test it. And I think that’s really important rather than us coming up with a new algorithm that is not recognized. We’ve been able to do an experiment to international standard organization guidelines. I think that’s been very powerful and was really a big strength of the study.

RF:  You’re an up and coming interventionalist. Do you have any advice for readers on research or career aspects?

JS: I have been fortunate to work with both John (Webb) and David (Wood) and have learnt a lot from them both, with regards to innovation. One of the main messages I learnt from John is to be a perfectionist and never settle for the status quo. I think that’s important, but also always challenge what is considered to be the standard dogma. But the main thing I’ve learned from John that I would give to other people is to always remain humble. John is a very famous interventional cardiologist but he’s still an extremely down to earth guy and always approachable. I think that’s the biggest thing I’ve learnt from him.

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