Case 10 — Electrocardiogram

ECG showing three simultaneously recorded leads (I, II, III). Basic rhythm is sinus arrhythmia at 85-115 bpm with normal MEA and normal P-QRS-T complexes. Frequent premature complexes (3rd, 5th, 9th, 12th) have abnormal configuration, no preceding P wave, are wider than normal sinus QRS complexes, and have T waves opposite in polarity. They depolarize at approximately 166 bpm.
Three-lead ECG (I, II, III). Sinus arrhythmia at 85–115 bpm with frequent premature ventricular complexes (3rd, 5th, 9th, 12th beats). The PVCs have abnormal configuration, no preceding P wave, are wider than normal, and fire at ~166 bpm.

The mean electrical axis is normal with normal-appearing P-QRS-T complexes. Despite markedly enlarged left atrium and left ventricle (seen on subsequent pages), there is no sign of enlargement on this ECG — a frequent finding. The premature complexes have an abnormal configuration, have no P wave in front of them, are wider than the normal QRS complexes, and have a T wave opposite in polarity to normal. There is an ectopic site in the heart competing with the sinus node, depolarizing at a rate of about 166 beats/minute.

Quiz

1. The premature complexes are most likely ventricular in origin (PVCs). How fast is this ectopic focus firing at?

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