This 61-year-old man with multiple serious medical problems is referred to the Emergency Department by his family physician. He has had a fever for one week and his blood cultures are positive for streptococcus viridans. He has a loud murmur of mitral regurgitation:

• Sinus rhythm with Mobitz II second degree AV block (3:2 AV conduction)
• Right bundle branch block

A second ECG is recorded 10 hours after admission:

• Sinus rhythm with complete heart block
• Escape wide QRS rhythm, probably junctional rhythm with right bundle branch block
• Ventricular rate 42/min

An electronic pacemaker is implanted:

• Electronic ventricular pacemaker (VVI)
• Underlying sinus rhythm with complete heart block
• Paced ventricular rhythm, 60/min)