You don't read the ECG.
You run the heart.

Existing ECG apps show you a picture and ask what it is. Depolarize gives you the conduction system and asks you to make the picture. The 12-lead is computed from activation vectors projected onto the lead axes, the AV node has a real refractory period with decremental conduction and concealed penetration, ventricular ectopy competes with sinus impulses, and every drug is a set of time-dependent modifiers on those same parameters.

That buys three things a question bank cannot. Reciprocal changes emerge: place one inferior injury vector and aVL depresses on its own. Pharmacology has consequences: adenosine in pre-excited AF strips the AV node's protection and the model degenerates to VF because the physics say so, not because a branch in a script says so. And the same engine scales: the His-bundle electrogram in Tier 7 is generated by the same event that produced the PR interval in Tier 1.

Three interaction modes: Build (recreate a target tracing by manipulating physiology), Bedside (a live patient whose hemodynamics respond to what you do), and EP Lab (intracardiac channels, calipers, programmed stimulation, ablation targets). Progression unlocks both content and the console itself: you cannot touch potassium until you have understood the QT.

Prototype notes: the vector model is a pedagogical simplification (single dipole per activation phase, three-phase QRS), not ECGSIM-grade forward modelling. Drug onset times are compressed for playability and labelled as such. Progress is held in memory for this prototype.

Depolarize comes from two internal medicine residents who kept running into the same wall: the ECG is taught as a set of pictures to memorise, and the physiology underneath gets explained once, on a whiteboard, and then never touched again. We wanted something you could break, fix, and break differently. So we built it.

• Dr. Jay GohriInternal Medicine Resident, University of Nevada, Reno School of Medicine
• Dr. Adhish BeriInternal Medicine Resident, University of New Mexico School of Medicine

We call ourselves The CardioLADs. The name is not serious. The intent is. We are early in our cardiology careers and want to grow alongside people who care about the same things: teaching that holds up under questioning, learning that does not depend on which program you matched into or what your institution can afford, and research that residents and students can actually take part in rather than watch from the back of the room. Depolarize is the first thing we have put out. It will not be the last.

If you teach ECGs, run a residency curriculum, or want to help validate this in a proper study, we would like to hear from you.

© 2026 Jay Gohri and Adhish Beri (The CardioLADs). All rights reserved. Depolarize, its conduction engine, curriculum, text and artwork may not be copied, redistributed or adapted without written permission.