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QRS duration

Column: qrs_duration_ms · Unit: ms · Measured on: lead II (default)

In one sentence: the QRS complex is the big spike of each beat, made by the two lower chambers (the ventricles) activating; its duration is how quickly the electrical wave spreads through them.

Everyday picture

The lower chambers have their own fast wiring, like an express train line, that delivers the signal to every part of the muscle almost at once. If part of that line is blocked, the signal has to crawl through ordinary muscle instead, like taking the slow local roads, and the QRS gets wider.

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What to notice:

  • A typical QRS is narrow, less than 3 small boxes. It is the fastest part of the beat.
  • Wide (bundle branch block): one of the two main wires to the lower chambers is blocked. In real ECGs the spike then also changes shape (for example notched "M" shapes in some leads); this simple drawing only shows the widening.

What's typical

QRS duration Plain meaning
under 110 ms typical: the fast wiring works
110–120 ms borderline
120 ms or more (3 small boxes) wide: the signal spreads slowly, e.g. a bundle branch block

Why it matters for synthetic ECGs

A narrow, sharp QRS needs a lot of detail in a short time, and generators that blur the signal tend to make it too wide or too rounded. A synthetic set whose QRS widths are systematically larger than the real ones looks "diseased" to a clinician even if the overall shape is right.

How ECGEN-Eval measures it

qrs_duration_ms is the time from QRS onset to QRS end, median over beats. It uses all leads at once, like commercial 12-lead programs:

  1. Add up how steeply every lead is changing (the spatial velocity). It is near zero on the flat parts and very high during the QRS.
  2. Around each R peak, the QRS is the stretch where that combined slope stays above 4 % of its range.

This needs no NeuroKit2. Against GE 12SL: typical error 6.4 ms, r 0.88, the same agreement as between two commercial programs (validation). With a single lead it is less accurate (r ≈ 0.5).

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