Electricity to ECG - How a Heartbeat Becomes Twelve Traces

Most ECG teaching starts at the paper and works backwards. This starts at the ion channel and works forwards, following one signal the whole way: a millivolt made across a cell membrane, summed into a heart vector, projected onto twelve axes, amplified, sampled, rounded, filtered, and finally drawn onto squares.

Fourteen modules, all driven by the same underlying engine, so a change made early shows up everywhere downstream. The limb leads use the standard geometry and the precordial leads the inverse Dower transform. Filters, sampling and quantisation are computed rather than illustrated.

Using it in a teaching session

The modules stand alone, so one can fill ten minutes at the start of a session. Taken in order they work as a short course.

The sampling and quantisation module is the one most worth your time. Trainees who have only ever seen finished tracings rarely realise how much of what they are reading is a reconstruction, and seeing a waveform degrade as the sampling rate drops makes the point better than any explanation.

Progress through the modules is remembered in the browser, so a trainee can work through it over several sittings.

What the model simplifies

Every trace is generated by a mathematical model, not recorded from a patient. The waveforms are deliberately idealised to make principles visible, which is exactly what makes them a poor substitute for practice on real tracings. Use it to build the mental model, then go and read real ECGs.