Electrocardiogram (ECG) showing complete heart block in a patient with syncopal episodes who previously had shown Mobitz II type AV block

The first two beats are paced. After the pacemaker is turned off, a normally conducted beat followed with a PR interval of 0.19 sec and a LBBB morphology. The next eight P waves fail to conduct and no lower pacemaker appears to assume control of the ventricles. Restarting the artificial pacemaker led to the QRS complex at the end of the rhythm strip.

Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright.