Wednesday, 23 January 2013

ECG of the Week - 21st January 2013 - Interpretation


This patient, unknown age & gender, presented with chest pain & dysponea.

 
 
Click to enlarge

Rate:
  • 36 - 38 bpm
Rhythm:
  • Regular
Axis:
  • QRS axis Normal (~0 deg)
  • Abnormal P wave axis
Intervals:
  • PR - Normal (~160ms) 1st & 6th complexes
  • PR - Normal (~180 ms) 2nd to 5th complexes
  • QRS - Normal (~80ms)
  • QT - 480ms (QTc Bazette ~ 370 ms)
Segments:
  • Slight ST Depression in V6 likely secondary to undulating baseline
Additional:
  • 2 Distinct P wave morphologies
    • 1st & 6th complexes
    • 2nd to 5th complexes
    • Abnormal axis in both morphologies
    • Varying degree of negative deflection in leads II, III, aVF, V1
  • U waves leads V2 & V3

Interpretation:
  • Ectopic Atrial Rhythm
    • 2 Distinct Ectopic Pacemaker Foci
    • Low Right Atrial Origin
Differentials:
  • Drug related e.g. Ca-channel blockers, Beta-blockers, other anti-arrhythmic
  • Ischaemia / Infarction
  • High vagal tone e.g. ? pain related
 Atrial Ischaemia / Infarction
  • Can occur without ECG evidence of ventricular ischaemia.
  • ECG Criteria for atrial infarction were proposed by Liu et al in 1961 following a case series review of six cases, link to the full article in reference section.
Liu Criteria for Atrial Infarction

Major Criteria
  • PR-segment elevation >0.5mm in leads V5 and V6 with reciprocal PR-segment depression in leads V1 and V2
  • PR-segment elevation >0.5mm in lead I with reciprocal PR-segment depression in leads II and III
  • PR-segment depression >1.5mm in precordial leads and >1.2mm in leads I, II, and III associated with any atrial arrhythmia
Minor Criteria
  • Abnormal P Waves
    • M-shaped, W-shaped, irregular, or notched
A case report and review of atrial infarction with a nice series of ECGs by Mendes et al. can be found here, this paper is also reference below.

References / Further Reading

 
Life in the Fast Lane
  • PR Segement / Atrial Ischaemia here
Papers
  • Liu CK, Greenspan G, Piccirillo RT. Atrial Infarction of the Heart. Circulation. 1961;23:331-338. PMID: 13762787  Full text here
  • Mendes RG, Evora PR. Atrial infarction is a unique and often unrecognised clinical entity. Arg Bras Cardiol. 1999 Mar;72(3):333-42. PMID: 10513045 Full text here
Textbook
  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.