Thank you to Alikuni Kllany from Toronto for donating these ECGs. They are from a 59-year-old man who has a history of hypertension and depression. Last year, he was on atenolol when he experienced a brief syncopal episode and bradycardia. He was taken off atenolol and started on amlodipine 5 mg. He also takes ramipril 10 mg, atorvastatin 40 mg, and tamsulosin .4 mg. He continues to have bradycardia and dizziness.
This example of sinus arrest, also called sinus pause, shows a spontaneous return to sinus rhythm. There are many mechanisms by which pauses can occur on the ECG. One concept for beginner students to grasp is that, if the pause contains the equivalent of regular R-to-R intervals, and the first complex after the pause is "on time", we can expect that the sinus node kept firing, but did not penetrate the atria (exit block).
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