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PR interval

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

In one sentence: the PR interval is the time from the start of the P wave to the start of the main spike, which is how long the signal takes to travel from the upper to the lower chambers.

Everyday picture

Between the upper and lower chambers sits a gate, the AV node. It deliberately holds the signal back for a moment so the lower chambers can finish filling with blood. The PR interval is the time from "upper chambers start" to "lower chambers start", and most of it is that wait at the gate.

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What to notice:

  • The flat stretch between the P wave and the QRS grows and shrinks; the P wave and the QRS keep their shape.
  • Long (first-degree AV block): the gate is slow, but every signal still gets through. On its own this is often harmless.
  • Short: the signal reaches the lower chambers early, sometimes through an extra electrical pathway that bypasses the gate.

What's typical

PR interval Plain meaning
under 120 ms (3 small boxes) short: the signal reaches the lower chambers early
120–200 ms (3–5 small boxes) typical
over 200 ms (5 small boxes) long: the gate is slow (first-degree AV block)

Why it matters for synthetic ECGs

The PR interval links two separate events (P and QRS) with a fixed rule. A generator that learned the shapes of the waves but not the timing between them shows up here as PR intervals that are too short, too long or far too variable.

How ECGEN-Eval measures it

For every beat, pr_interval_ms is the time from P-wave onset to QRS onset; the recording value is the median over beats.

  • QRS onset comes from all leads together: where the combined slope of the leads rises above 4 % of its range before the R peak.
  • P onset comes from NeuroKit2's peak-prominence delineator on every lead (the median across leads), refined to where the P wave reaches 15 % of its height.

Needs NeuroKit2 (NaN without it). Against GE 12SL: typical error 8.5 ms, r 0.87 (validation).

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