Lead I and aVL shows wide notched QRS complexes suggestive of left bundle branch block. PR interval for the sinus beat is 200 ms, at the upper limit. Rhythm strip shows sinus bradycardia with junctional escape beats (blue arrow) without preceding P waves, but same QRS morphology as the succeeding sinus beat (violet arrow). The sequence of junctional escape followed by a sinus capture beat continues throughout the rhythm strip. This constitutes an escape – capture bigeminy.
Other common varieties of bigeminy are:
Ectopic bigeminy sequence can be seen when sinus beat alternates with either a ventricular or supraventricular ectopic beat. Block bigeminy is seen in 3:2 sinoatrial or atrioventricular blocks. In echo bigeminy, the second beat is an echo beat.