An approach to the patient with a suspected tachycardia in the emergency department.

Patients present to the emergency department with either an ongoing tachycardia or a history suspicious of a tachycardia. Either way, the tachycardia needs to be documented, preferably on a 12-lead electrocardiogram (ECG) for diagnosis and management. If a tachycardiais not documented, a careful history of the palpitations should be taken to see if further monitoring and investigations are required. If a tachycardia is confirmed on an ECG, the clinician needs to classify it according to two variables: (i) regularity of the rhythm; and (ii) QRS width. This will allow a differential diagnosis to be made.