Animated heart-and-trace view of the cardiac electrical cycle: P, QRS, ST and T phases each light up the corresponding chamber and waveform segment.
A free, animated ecg cardiac cycle (animated) you can read here or embed on any website, from Scrollchart.
ECG Cardiac Cycle (Animated)
Atria depolarizing
Ventricles depolarizing
Plateau (contraction)
Ventricles repolarizing
Every heartbeat is one trip through this electrical cycle. The SA node fires, the atria contract, the AV node briefly delays the signal, the ventricles contract, and the muscle resets. The PQRST is the ECG fingerprint of that sequence: P for atrial depolarization, QRS for ventricular depolarization, T for ventricular repolarization, with the ST segment representing the brief plateau in between.
Knowing what each segment represents lets you read an ECG as a story rather than a squiggle. A missing P wave hints at AFib. A widened QRS hints at a bundle branch block. ST elevation is the cardinal sign of an evolving infarct. T wave inversion suggests ischemia or strain.
Cardiac myocytes have a resting membrane potential around minus 90 mV maintained by the Na/K ATPase and inward-rectifier K+ channels. Depolarization sweeps through gap junctions: atrial cells fire first (P wave, ~80 to 100 ms), the AV node delays the signal by ~100 ms (PR segment), then the bundle of His and Purkinje fibers fire the much larger ventricular mass nearly simultaneously (QRS, ~80 to 120 ms).
The ST segment is the plateau phase: ventricular cells are fully depolarized, calcium-induced calcium release is in full swing, and the muscle is mid-contraction. The T wave is repolarization driven by delayed-rectifier K+ channels (IKr, IKs) restoring the resting potential. The cycle then repeats 60 to 100 times per minute at rest.
Good for
Cardiology teaching
Patient education before stress tests
Editorial pieces on heart-rhythm topics
Source & accuracy
This ecg cardiac cycle (animated) is an editorial illustration built to represent the concept accurately. Where it shows figures, they are typical or representative values chosen to make the relationship clear, not a single underlying dataset. The diagram and its explainer are reviewed and maintained centrally, and updated over time as understanding improves.
Matching each waveform to a chamber
An animated cardiac cycle view links the surface ECG tracing to the electrical events inside the heart. The P wave corresponds to atrial depolarization, the electrical signal spreading across the atria that drives them to contract. The QRS complex marks rapid depolarization of the much larger ventricular muscle.
The T wave then reflects ventricular repolarization, the recovery phase that resets the cells for the next beat.
What the ST segment represents
Between the QRS and the T wave lies the ST segment, a period when the ventricles are fully depolarized before repolarizing. On a normal trace it sits near the baseline, which is why deviations from baseline draw clinical attention.
Linking the trace to chamber activity helps build intuition, but interpreting an actual ECG for diagnosis is the role of a qualified clinician. This is general educational information, not medical advice.
Embed this diagram
Add this animated ecg cardiac cycle (animated) to your own site. Copy one line of HTML, or use the embed builder for theme and sizing options.
Reference
What this is
A free, embeddable, animated ecg cardiac cycle (animated) for any website.
Who uses it
Medical educators, Patient-info sites, Health blogs.
How to embed
Copy one line of HTML. No signup. No watermark. Works in WordPress, Webflow, Ghost, Substack, plain HTML.
File size
iframe embed, ~80 KB gzipped (loads on demand, does not block your page paint).
License
Free forever. Editorial explainer text included; updated centrally over time.
Copy the universal HTML snippet, the WordPress shortcode, or an iframe fallback -
see the WordPress plugin page for details. Any format keeps
the same Core Web Vitals profile and the same explainer text.
By embedding, you acknowledge the diagram and explainer text are served from scrollchart.com and may be updated from time to time to reflect new research or to link to relevant sources within the explainer.
Frequently asked questions
Where can I get a free animated "ECG Cardiac Cycle (Animated)" for my website?
Scrollchart provides "ECG Cardiac Cycle (Animated)" as a free, embeddable animated diagram you can add to any website with one line of HTML. No signup is required and there is no watermark. The diagram and its explainer text are served from scrollchart.com, so the embed stays current without any maintenance on your end.
How do I embed a ecg cardiac cycle (animated) diagram in a health or wellness blog?
Copy the HTML snippet from the Scrollchart diagram page and paste it into any post or page in your CMS. It works in WordPress, Webflow, Ghost, Substack, and plain HTML without any plugin or account. The diagram renders as animated SVG directly in your page, so search engines can index the accompanying explainer text.