This study was set in the adult ED of Maimonides Medical Center, an urban teaching hospital in Brooklyn, NY with an annual ED census of more than 120,00 patients. A convenience sample of adult patients age 18 or older presenting with a supraventricular tachydysrhythmia were evaluated for enrollment. Eligible patients had to have a 12-lead electrocardiogram (ECG) showing atrial fibrillation or atrial flutter with a ventricular rate of greater than or equal to 120 beats per minute. Data collected included demographics, medical history, vital signs and electrocardiogram findings. All patients were immediately evaluated by the treating physician utilizing ACLS protocols. At the discretion of the treating physician, intravenous adenosine was administered in order to facilitate identification of the underlying supraventricular tachydysrhythmia. All patients were attached to a monitor that displays cardiac rhythm, heart rate, blood pressure and oxygen saturation.