A 69-year-old woman presents to the emergency department complaining of severe palpitations, dyspnea, and weakness for the past two hours. During the past year, she experienced 4-5 milder episodes that subsided spontaneously in less than one hour. She has no other cardiac complaints and had been active and otherwise well:

• Atrial fibrillation with rapid ventricular response – 152/min
• Nonspecific ST abnormality

There are flutter-like atrial waves, however their pattern is quite variable and irregular. They are best seen in lead V1, while the waves of typical flutter are best seen in the inferior leads. The ventricular rhythm is very irregular. These findings are typical of atrial fibrillation.

Half an hour after arriving in the Emergency Department, the arrhythmia subsides spontaneously and the patient becomes symptom-free:

• Sinus rhythm – 89/min
• Normal ECG

Atrial fibrillation is a common arrhythmia in the population above the age of 60. It may occur as an isolated cardiac problem, without evidence of structural heart disease. 

The patient remained symptom-free for several hours. Her physical examination, chest X-ray, and echocardiogram were normal. She was discharged  home and referred  to the arrhythmia clinic for further investigation and follow-up.