Category Archives: Science


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!

My Trial of the “Geek to Freak” Weight Training Technique

I’ve learned a lot from a guy many people love and many others love to hate. There’s no question he does things in controversial ways, and I don’t doubt the reports of his ruthlessness when it comes to his business ends. Nonetheless, he’s dispensed a lot of sound (if not always original) advice.

The guy I’m talking about is Tim Ferriss. He wrote a blog post a little while back called “From Geek to Freak: How I Gained 34 lbs. of Muscle in 4 Weeks”. I found that post at a time when I’d been struggling to figure out how to weight train correctly. I thought surely there must be some good scientific information on weight training, but what I found online (I later found a pretty good book) was a massive mish-mash of pseudoscience and mythology.

What I wanted was to build some muscle mass to improve my strength and appearance. The only thing that’s ever worked for me before for that purpose was lap swimming, and it took a ton of time and a nearby pool. I have neither of those now, so I decided to give Tim’s technique of lifting large weights for only a few reps a try. It promised significant improvement in only about 30 minutes per workout, twice per week. I was skeptical, and my wife was doubly skeptical.

To avoid as much bias as I could, I logged my progress in a Google Spreadsheet and published it here. I logged other observations on Think, Try, Learn’s new “Edison” platform, also publicly visible: Attempting the “Geek to Freak” muscle building technique.

The short version: it worked splendidly! Both my wife and I were pleasantly surprised at the results.

Long version:

It was very important to keep my protein and overall calorie intake up to the level I was burning. Using whey protein I maxed out my safe weight training protein allowance every day, and I used to track all of my nutrition (which I do when losing weight anyway). I noticed that whenever I didn’t eat enough calories I stalled out pretty badly. If I hadn’t been tracking my nutrition and my lifting stats I probably would have been mystified as to the reason for my trouble, or just frustrated that I wasn’t making progress. I’ve had that problem before, and realized in retrospect that I was able to gain muscle well while swimming because I was eating things like two steaks or an entire wok of home-made General Tso’s Chicken every night for dinner. (Sort of a ‘duh’ thing now, right?)

At first I was trying to both lose fat and gain muscle at the same time. That worked for a week or two, but then I quickly stalled out on the muscle gain. I read a bit about this and it seems that when you first start a weight training regimen, there’s a ‘honeymoon’ period where your untrained muscles grow to meet the new load. After that period, I had to give up on losing fat simultaneously. However, now that I’m taking a break I’m finding it’s easier to lose weight as my increased muscle mass burns more calories per day even at rest. (I injured my leg stepping over a baby gate and then had to travel a bit. I’m planning on getting back to the weight training soon.)

I tried another one of Tims’ ‘hacks’ to improve my reading speed and found less dramatic results. His metrics for that technique are biased in favor of finding an improvement, even if there isn’t really one. I also logged my results carefully there and abandoned the technique after a few trials.

In the end, the Think, Try, Learn treat-everything-as-an-experiment approach worked well for me in vetting suggested lifehacks. I’m going to continue using both the weight training technique when I want to gain muscle, and the TTL experiment approach for trying new things.

Have you tried any experiments like this?

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.