PR segment

The PR segment is the usually flat line between the end of the P wave and the start of the QRS complex

Reflects the delay between atrial and ventricular depolarization

Used in some studies and guidelines as the isoelectric or reference line for which other waveforms are measured (also see: TP segment)

PR segment depression (relative to TP segment) is seen in conditions such as pericarditis or atrial ischemia (STEMI)

PR segment elevation (>0.5 mm) or depression (>0.8 mm) may be seen in MI suggesting atrial infarction or ischemia, and is associated with adverse outcomes