Case 14 — ECGs

First Visit

ECG recording of leads II and III at 25 mm/sec, taken 25 minutes after 0.04 mg/kg atropine subcutaneously. Shows sinus bradycardia with episodes of sinus arrest and escape beats. The ECG before atropine was not different.
Leads II and III (25 mm/s). Recorded 25 minutes after 0.04 mg/kg atropine SC. The pre-atropine ECG was not different.

Second Visit

ECG recording from the second visit, also taken after atropine administration. Shows more pronounced sinus arrest with long pauses and infrequent escape beats.
Leads II and III (25 mm/s), second visit. Also recorded after atropine administration. More pronounced sinus arrest with long pauses.

Quiz

1. What is the primary rhythm abnormality that occurs multiple times in the top trace and is most marked after the second QRS complex on the bottom trace?

2. What is the general name for the QRS complexes that follow each pause?

3. Based on the configuration of these complexes, where do they most likely originate from?

4. How long is the pause after the second complex in the bottom trace?

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