Subtyping cardiac arrest with ECG waveforms

A patient is rushed into the ER, unconscious and in cardiac arrest. As the physician begins the resuscitation, she knows only that the patient’s heart has stopped—but nothing else. What happened to cause the arrest? What immediate actions need to be taken? And what will happen to the patient? One of the only pieces of data available to the emergency physician in this situation is the electrocardiogram (ECG), which measures the electrical activity of the heart. Physicians use this to determine which immediate actions are needed: most importantly, does the patient need to be shocked (cardioverted), or need some critical medication to restart the heart. This rich signal might also contain other clues: about why the heart stopped, what physicians can do in the ER to give the patient the best possible chance of surviving, and the likelihood that a patient who survives will have a normal life, without profound physical or neurological impairments.