ECG Interpretation
Read a rhythm strip or a 12-lead ECG, choose the rhythm — and for some cases the next step — then check. The answer shows the tracing annotated beat by beat, a systematic read and the guideline behind it.
Tracings are computed by the TracingsMD physiology engine — simulated, not patient recordings, and not for diagnosis. This is educational practice, not a clinical examination.
Interpretation · 26 cases
New to ECG reading? Start at Beginner, and use Theory or the Basics lessons when a term is unfamiliar. Cases come in random order, and the same rhythm can return as a different engine recording — the rate and timing change, so you read the ECG, not a remembered picture. Not sure? Use “Show answer” to see the explanation without scoring.
P wave (navy)P wave not conducted (red)flutter wave (purple)shaded QRS, amber when 120 ms or widerPR bracket, msteal bracket = RR interval, msQT bracket with the same beat's QTcPVC / PAC label = early beatvertical tick = pacing spike (red: no capture; grey: in the refractory period)red outline = ST elevation ≥ 0.1 mV at J+60 msblue dashed outline = ST depression ≥ 0.08 mV
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Your score reflects the answers checked in this attempt. It does not assess clinical competence.
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How these cases are made
Every tracing is recorded output of the TracingsMD physiology engine (Lead II and other leads at 500 samples per second, 25 mm/s, 10 mm/mV) — no patient recordings and no generative AI. Annotations are placed from the engine's own beat events: where it started each P wave and QRS complex, which P waves it did not conduct, and the intervals it measured. Measurements are model values, not clinical measurements.
Each case has one or more recordings of the same rhythm at different rates. Answers follow the references listed with each case; management answers follow the AHA 2025 adult advanced life support algorithms, as on the ACLS Scenarios page. Patterns are teaching examples; real tracings vary more, and a single lead cannot resolve every rhythm.