This ECG was recorded from an essentially asymptomatic 55-year old male after his GP noticed that he was bradycardic during a routine check-up. He had no family history of note, was not taking any medication and his blood pressure was 130/90 mm Hg. Does the ECG suggest any particular diagnosis?

Note that the chest leads were recorded at half standardisation (5 mm/mV).

Dr Dave Richley, 
Associate Lecturer
Newcastle University