Complete heart block with severe bradycardia

Continuous ECG strip recording at 25 mm/second, showing severe bradycardia (heart rate 33) and 3rd degree (complete) heart block. The first four QRS complexes have a right bundle branch (RBBB) morphology, the fifth shows a left bundle branch (LBBB) morphology, and the sixth again shows RBBB. The alternating bundle branch escape rhythm further confirms advanced heart block requiring urgent treatment. Note that the last one second of the top tracing panel shown in darker grey is "repeated," in the first one second of the bottom tracing.