Electrocardiogram (ECG) strips showing junctional premature beats

Three simultaneous electrocardiographic surface leads V1, II, and V5 show a junctional premature beat (asterisk). In panel A, there is a sinus P wave seen in lead II just prior to the junctional premature beat, which alters its initial deflection (arrow). The junctional premature beat has a QRS morphology that is identical to that of the sinus beat. In panel B, a sinus P wave is seen immediately after the junctional premature beat in lead II (arrow). The junctional premature beat has a QRS morphology which is slightly different from the sinus QRS complex.