ECG of the Week - 12th October 2015 - Interpretation

The following ECG's are from a 17 yr old male who presented with palpitations for the last hour. He is normal fit and well. He denies taking any medications or drugs.
I don't know the exact time frames between these ECG's and what treatment, if any, was instituted between them.

ECG 1
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Key points:

• Narrow complex tachycardia rate ~162 bpm
• Atrial activity visible in V1 with upright narrow wave which are inverted in the inferior leads
• Irregularity noted in initial portion of the ECG and within leads aVR, aVL, aVF

DDx:

• Atrial flutter
• Atrial tachycardia 

ECG 2
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Key points:

• Initial 10 complexes irregular without organised atrial activity
• Followed by single sinus complex then 2 ventricular complexes
• Period of flutter / atrial tachycardia
• Pause ~1.2 seconds followed by sinus complex

ECG 3
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Key points:

• Initial 5 complexes sinus - note p wave morphology is distinctly different than that seen in the first 2 ECG's
• Premature atrial complex then initiates the onset of a narrow complex tachycardia with a brief 'wind-up' period of rate increase

ECG 4
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Key points:

• Regular narrow complex tachycardia ~140 bpm
• Inverted atrial activity in inferior leads with small upright atrial activity in lead V1
• Inferior 'saw-tooth' pattern looks most like atrial flutter

ECG 5
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Key points:

• Finally back in sinus !
• Otherwise largely unremarkable ECG

References / Further Reading

Life in the Fast Lane

• SVT
• Atrial Fibrillation
• Atrial Flutter
• Premature Atrial Complex

Textbook

• Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.