Johannes Enevoldsen

Small blog post on how to automate model building for mechanical systems using ModelingToolkit. #julialang

michielstock.github.io/posts/2025/p...

Drowning Doesn’t Look Like Drowning Drowning is not the violent, splashing call for help that most people expect.

Thanks for the reminder @janemunday.bsky.social. Every summer, I repost this article DROWNING DOES NOT LOOK LIKE DROWNING. To date, I know of FOUR kids who were saved after someone who'd clicked on the link learnt how to spot actual drowning. Take time to read and pass on.

slate.com/technology/2...

Great ... though it would have been nice to make this show 0✅

I have the same problem. If I only ever intend putting it on GitHub, is it reasonable to just ignore it? Escaping all these characters will make the code a lot less readable.

Thank you. With such praise, it is hard not to:
RSS: jenevoldsen.com/index.xml

It would be a reasonable regulatory mechanism, that lactate signals increased oxygen demand and raises CO, though I don't know whether it is possible, or even meaningful, to distinguish whether lactate is both fuel and a signal, or just fuel.

Cardiovascular effects of lactate in healthy adults - PubMed https://clinicaltrials.gov/ct2/show/NCT04710875 . Registered 1 December 2020.

Just found that the same group also did this study, showing that lactate increases CO in healthy adults. pubmed.ncbi.nlm.nih.gov/39825426/

bsky.app/profile/johs...

Absolutely fascinating! We know the heart switches to lactate as energy substrate in shock, could there be a clinical benefit from lactate infusion in human cardiogenic shock? #emimcc #cccsky

Incredible effect sizes. Do we know what lactate does in a healthy heart? From a teleological perspective, it would make sense that lactate has a positive inotropic effect, regardless of it being a substrate. Simply as a signal of hypoperfusion.

I'm sorry you had to experience that. Unfortunately I don't know what determines which treatment is tried first, or whether e.g. cardioversion can be expected to work if the condition reoccurs, when it didn't work the first time.

My cardiac arrhythmia simulation now also simulates how a reentrant loop can be terminated by increasing refractory time as suggested by @empoisonpharmd.bsky.social

Direct link to the updated part:
jenevoldsen.com/posts/excita...

✨ It's new samwho visual essay o'clock! ✨

Reservoir sampling is one of my favourite algorithms. It allows you to sample from a set without knowing the size of that set.

I try to assume no prior knowledge, and use no scary math notation. Just beautiful visuals.

Let me know what you think! ❤️

I just want to say I use this constantly at the bedside when dealing with patients who have arrythmias to explain how they propagate.

would LOVE LOVE a model where increasing refractory terminates reentrant rhythm so I can show how diltiazem terminates SVT.

such an amazing tool, thank you

Thank you! So nice to learn that it is actually read and used.

Good idea with a sim, where the arrhythmia is stopped with meds. It shouldn't be too hard to make a sim, where refractory time can be prolonged.

I'll give you a heads up when I find the time to implement it.

A 10-minute movie in a 6.3-second looping GIF.

Movie: Sprite Fright (#Blender open movie): studio.blender.org/projects/spr...

Code (#JuliaLang and @makie.org)
gist.github.com/JohannesNE/2...

For AVNRT, some people just have a physiological variant where the AV node is split in a slow pathway and a fast pathway.

For VF and AFib, there are many proposed mechanisms, slow repolarization could occur in areas with ischemia. Reduced conduction due to e.g. fibrosis plays a large role as well.

Thanks. Just scrolled through some of your articles. Really impressive! I look forward to doing a deeper dive in the coming days.

Thanks.

I'll add that next time I update it. Might be a while before post #2 though 😉

Fellow #JuliaLang enthusiasts in Europe, I've got 4 words for you.

JuliaCon Local Paris 2025

Yes, it's happening. Like the global @juliacon.bsky.social event, but with more croissants. Stay tuned!

This would of course require a local LLM for privacy reasons.

- Why is this patient not on losartan?
- Has this pt with "COPD" ever done a pulmonary function test?
- What penicillin-like drugs has this pt with registered penicillin allergy received since the penicillin-associated rash 30 years ago?

Where I could really see a place for LLMs in medicine right now, is not for decision-making, but for understanding a patient's medical records in a reasonable time.

- Find plans for this admission, that were never followed up upon.
- Give a short review of the pt's medical history.
...

Maybe responders interpret "clinical decision-making" differently.
"What is a good starting dose of propofol for anesthesia of a 4 yo?". Seems dangerous.

While "suggest diagnoses for a patient with 4 weeks of cough, stuffy nose and malaise" may help the doc consider some less common disorders.

The Hypotension-Prediction Index--a convoluted way of predicting hypotension by...checking whether the MAP is low--fails once again. Shocker.

"HPI-guided hemodynamic therapy did not reduce the incidence of postoperative AKI or overall complications [vs] standard care."

Like, "increase this slider until fibrillation stops."

Thank you. I actually considered that it would be interesting to make a simulation of the different anti-arrythmic class effects on a fibrillation.

The current simulation could actually be modified to show the effect of class III anti-arrythmics (prolong refractory) on fibrillation.

Thank you!

Johannes Enevoldsen - Excitable cells A demonstration of how reentry tachyarrhythmias can develop in a system of excitable cells.

jenevoldsen.com/posts/excita...

There is also a simulation of atrial fibrillation.