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.