Key Learning Points
Intervals and Segments
PR Segment Page 2
- The PR Segment resides between the end of the P Wave and the start of the Q and R Wave.
- The PR Segment represents polarization of the AV Node and top portion of the HIS Purkinje system.
- The AV node contains specialized cells responsible for delaying the impulse traveling to the ventricles
allowing the atriums time to contract and eject their contents into the ventricles before the ventricles contract.
PR Interval Page 3
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The PR Interval has three parts:
Depolarization of the right and left atrium(a).
Depolarization of the AV Node(b).
Depolarization of the top portion of the HIS Purkinje System(c).
- The PR interval is measured from beginning of the P wave(d.) to onset of the QRS complex(e).
- The normal duration of the PR interval is 0.12 sec to 0.20 sec.
