Scenario: This continuous lead II rhythm strip was obtained in a 25-year-old woman admitted to the intensive care unit for intracerebral hemorrhage. The patient presented to the emergency department with a headache after a skateboarding accident. The patient stated that she “bumped” her head during the accident. The bedside monitor alarmed for bradycardia/pause. Upon assessment, the patient was alert, oriented, and hemodynamically stable.

Interpretation: Sinus bradycardia at 55 beats per minute, nonrespiratory sinus arrhythmia. There are also intermittent U waves throughout this rhythm strip (see end of second beat).

During the entire rhythm strip, the heart rate never exceeds 60 beats per minute, hence the diagnosis of sinus bradycardia. There are 2 types of sinus arrhythmia: respiratory and nonrespiratory. In the respiratory form, sinus arrhythmia typically varies with respirations, and the heart rate (RR interval) increases with inspiration and decreases with expiration. In this example, the irregularity of the rhythm...

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