Increased automaticity of the AV node.

Scenario: This lead II ECG rhythm strip was obtained in a 52-year-old male patient being treated in the neurological intensive care unit for subarachnoid hemorrhage. The patient was unconscious and therefore could not be asked whether he was experiencing symptoms. His vital signs were stable: His blood pressure was 125/70, heart rate was 80 beats per minute (bpm), and he was receiving mechanical ventilation at 20 breaths/minute. ECG PUZZLER A regular feature of the American Journal of Critical Care, the ECG Puzzler addresses ECG interpretation for clinical practice. We welcome letters to the Editors regarding this feature.