PR segment abnormalities occur in two main conditions:
- Atrial ischaemia
The characteristic changes of acute pericarditis are:
- PR segment depression.
- Widespread concave (‘saddle-shaped’) ST elevation.
- Reciprocal ST depression and PR elevation in aVR and V1
- Absence of reciprocal ST depression elsewhere.
NB. PR segment changes are relative to the baseline formed by the T-P segment.
- PR segment depression in V5 due to acute pericarditis (note also some concave ST elevation)
- PR elevation in aVR due to acute pericarditis (note the reciprocal ST depression)
- PR segment elevation or depression in patients with myocardial infarction indicates concomitant atrial ischaemia or infarction.
- This finding has been associated with poor outcomes following MI, increased risk for the development of atrioventricular block, supraventricular arrhythmias and cardiac free-wall rupture.
Liu’s criteria for diagnosing atrial ischaemia / infarction include:
- PR elevation >0.5 mm in V5 & V6 with reciprocal PR depression in V1 & V2
- PR elevation >0.5 mm in lead I with reciprocal PR depression in leads II & III
- PR depression >1.5 mm in the precordial leads
- PR depression >1.2 mm in leads I, II, & III
- Abnormal P wave morphology: M-shaped,W-shaped,irregular,or notched (minor criteria)
PR depression in inferior STEMI indicating concomitant atrial infarction
- Profound PR-segment depression in inferior leads with (A) and without (B) clear-cut TP segment in acute inferior myocardial infarction. Note also ST-segment elevation in inferior leads. (Reproduced from Jim et al.)
Measurement of PR depression
- Measurement of PR-segment depression with (A) and with- out (B) clear-cut TP segment. (Reproduced from Jim et al.)
- Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography
- Hampton, JR. The ECG In Practice, 6e
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric, 6e
- Wagner, GS. Marriott’s Practical Electrocardiography 12e
- Chan, TC. ECG in Emergency Medicine and Acute Care
- Wang, K. Atlas of Electrocardiography
- Mattu, A. ECG’s for the Emergency Physician
LITFL Further Reading
- ECG BASICS — Waves, Intervals, Segments and Clinical Interpretation
- ECG A to Z by diagnosis –alphabetical diagnostic approach to the ECG
- ECG CLINICAL CASES — ECG’s placed in clinical context with a challenging Q&A approach
- 100 ECG Quiz — Self-assessment tool for examination practice
- ECG Reference SITES and BOOKS — the best of the rest
- LITFL ECG IMAGE Database — Searchable database of LITFL ECG’s
- ECG and Cardiology Eponymous Syndromes — Cheats guide to eponymous emancipation
- ECG Exam Template — a framework for answering ECG exam questions.