This 43-year-old woman is referred to the Emergency Department by her family doctor because of an abnormal ECG recorded during a routine assessment. She endorses rare episodes of paroxysmal rapid palpitation during the past 2-3 years, lasting 15-20 minutes, but otherwise she has no cardiac complaints and exercises regularly without discomfort:

• Atrial tachycardia with Mobitz I second degree AV block
• Atrial rate 126/min, ventricular rate 100/min

The patient was monitored in the Emergency Department. She remained symptom-free, however a repeat ECG 25 minutes later differed from the first:  

• Sinus rhythm, 74/min
• Normal ECG

The patient was referred to the Arrhythmia Clinic. Physical examination, chest X-ray and echocardiogram were normal. 24-hour Holter monitoring demonstrated frequent premature atrial complexes, and episodes of ectopic atrial rhythm, the longest of which lasted 3 hours, with a maximum heart rate of 102 bpm. There were several brief episodes of atrial tachycardia lasting less than 30 seconds, with a maximum rate of 135 bpm and occasional Mobitz I AV block. There were no episodes of abnormal bradycardia.  The patient remained asymptomatic. It was felt that the patient had benign ectopic atrial rhythm and atrial tachycardia, and no medication was prescribed.

One year later, she was reassessed in the arrhythmia clinic. She reported rare brief episodes of mild palpitations lastig several seconds. She denied dyspnea, presyncope, or weakness. She remained normally active. Holter monitoring showed results similar to those of the previous year. She will be followed by her family physician, and reassessed in the Arrhythmia Clinic annually.