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PR-segment and PR-Interval changes

PR-Segment

ConditionEKG changes
Normalflat and isoelectric
Pericarditisdepressed in all leads except aVR and V1 where it is elevated
Atrial infarct/ ischemia (Liu’s Major criteria)Elevation of the P-Ta segment of over 0.5 mm in V5 and V6, with reciprocal depression of the same segment in V1 and V2.
Elevation of the P-Ta segment exceeding 0.5 mm in lead I, with reciprocal depression of the same segment in leads II or III
P-Ta segment Depression greater than 1.5 mm in the precordial leads and 1.2 mm in leads I, II, and III, particularly in the context of any atrial arrhythmia.

PR Interval

ConditionEKG Changes
NormalPR interval = 0.12 to 0.2 seconds (3-5 small squares)
First degree AV blockPR interval > 0.2 seconds
Second Degree Type 1Progressively prolonging PR segment before a dropped QRS
Preexcitation Syndromes: Wolff-Parkinson-White (WPW) and Lown-Ganong-Levine (LGL)
Junctional Rhythm
PR interval < 0.12 seconds

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