Single-lead electrocardiogram (ECG) showing atrial bigeminy and blocked atrial premature beats (APBs)

The single channel electrocardiographic recording shows a sinus P wave (P) followed by an atrial premature beat (P') in a repeating pattern, termed atrial bigeminy. The P' does not result in ventricular activation since conduction is blocked within the atrioventricular node (blocked atrial premature beat).