Beat anatomy
Click any part of the beat to open it isolated — what it is, its normal shape in this lead, and how the pattern bends it. Simulator · Lessons
One generated beat of lead II, calibrated 1 small box = 40 ms × 0.1 mV. Unit boundaries are teaching approximations from the R-peak + measured PR/QRS/QT.
Conduction & flow
Where the current is while the beat is written — press play, scrub, or click the trace. Clicking a part of the beat above highlights the structures that make it.
SA node fires, the atria depolarise (P), the AV node holds the wavefront (PR), then the His-Purkinje system activates both ventricles almost simultaneously — a narrow QRS.
Schematic conduction path (Durrer1970, Kligfield2007, Surawicz2009) — for teaching, not diagnosis.