Category Archives: Biomedical Engineering

Biomedical Engineering

Cool story on ablation outside of treatment guidelines

I read Dr.Wes’ blog to get better insight into the professional lives and needs of clinical cardiologists and EPs. This week, Dr.Wes posted an excerpt from and commented on this interesting account of ablation in a baby. I’ll repeat the excerpt because it’s worth showing:

All of the planned means of tackling Stellan’s SVT today during his ablation failed initially. Heart block was induced each and every time from each and every angle they tried to ablate. Dr. A and his team were left with little choice but to ablate Stellan’s AV node in order to get rid of his accessory pathway. But before they did, one of Dr. A’s colleagues threw out a wild idea.

“Let’s try to go through his aorta.”

Not in the plan. Not even in the possible or hypothetical plans. Not considered safe or feasible or wise on a 10 kilo baby. But with few options left before destroying Stellan’s node, they decided to risk it.

To be honest, I’m glad I didn’t know about it at the time.

So from his groin, they threaded the catheter up into his aorta, down into his atrium and through his valve toward his ventricle. From that angle, even though Dr. A said they were in the exact same spot as they’d tried ablating earlier, there was a money shot. He tried cryoablation. It started to zap his SVT with no heart block. So he tried a little more cryo. Again, no heart block.

So Dr. A pulled out the big dog. The radio frequency ablation catheter. His ultimate goal was to get 2 to 3 seconds of ablating done, even if it destroyed his node.

1 second. 2 seconds. 3, 4, 5.

From that angle, through the aorta, Stellan’s AV node remained untouched.

Unbelievably, Dr. A was able to crank up the wattage and ablate Stellan’s extra pathway for one solid minute before declaring his pathway dead on arrival.

And his AV node is as happy as the day is long.

Dr.Wes aptly notes that this sort of thing does not meet with the idealized always-follow-the-guidelines-or-else strategy being espoused by Washington of late. On the one hand, I’m all for evidence-based medicine and adhering to known best practices. On the other, this is a clear example of the variability that occurs from patient to patient, and the importance of experience and skill on the part of physicians enabling them to know when to bend or break the guidelines. Bravo.

Excellent review of cardiac ionic models on Scholarpedia

Some of our lab’s “competitors” have a really nice article covering many many of the existing cardiac ionic models up on Scholarpedia, with illustrations and even java applets and movies.

The article is entitled Models of cardiac cell [sic].

Kudos to Drs. Fenton and Cherry for the excellent article, it looks like it was quite a lot of work to put together!

Second CSM Demo – Activation Mapping and More

Today the latest CSM demo video went live on the CardioSolv site. It showcases the use of our mapping interface, which makes it easy to create useful maps of activity in simulation models.

It’s currently non-trivial to show movies in papers, so instead we do time-lapse type things called activation maps. These show the activation times as a series of lines (‘isochrones’ or ‘isochronal lines’, meaning that all of the points on the line are activated at the same time) or bands of color representing the same thing. We can extend this to also show repolarization times, or non-sequential data such as action potential duration maps and dominant frequency maps.

Here’s a sample activation map of a wave moving across a sheet from right to left:

Activation Map Right to Left

Activation Map Right to Left

And here’s one of a spiral (this with 20ms isochrones):

Activation Map of a Spiral Wave

Activation Map of a Spiral Wave

To give you an idea of the correspondence between an activation map and a movie of the simulation, here’s a movie of that spiral:
Spiral Wave

There’s a lot more to this — for instance, deciding when a cell has activated or repolarized, and back-end processing. We use a program I wrote that does the analysis in parallel, making it rather quick to analyze even huge datasets, provided you have the computing power.

If you have any questions about the process I’d be happy to answer them here or on the CardioSolv post.

First CardioSolv Simulation Manager Demo

Today I’m really excited to finally show you something that’s been in the works, both in implementation and in the planning stages, for a long time. The CardioSolv Simulation Manager.

Running cardiac electrophysiology (and mechanics) simulations has traditionally been really complicated. It involved learning a bunch of UNIX command-line tricks, dealing with queuing systems and their associated script files, and so on. Furthermore, there are many, many options in a sophisticated cardiac simulator, and the novice user (and even the expert) can easily get lost in all of the choices.

We’ve taken years of experience setting up, running, and analyzing simulations to build a really cool (excuse my excitement) web interface that handles all of the dirty work, and guides the user through the important choices when running simulations.

The video below is my first demo. In it, I demonstrate how to create a plane wave moving across a sheet of tissue, then create a spiral wave, all from the web interface.

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