A 72-year-old man with known slow heart rate for many years and good exercise tolerance, is in the office of his family doctor for a routine check-up:

• Abnormal P axis, compatible with ectopic atrial rhythm (rate 50/min)
• No other abnormalities

The P wave is negative in II, III and aVF in keeping with an ectopic pacemaker located in the lower atrial region. The PR interval is 190 msec. An ectopic atrial rhythm may be seen both in individuals without structural heart disease and in cardiac patients. It is often transient.

If PR interval is <120 msec. the rhythm is considered to originate in the area of the AV junction (junctional rhythm).
The last ECG tracing of this patient (1 years ago) showed sinus bradycardia, 53/min. Chronic sinus bradycardia is common in healthy asymptomatic elderly subjects.