This 68-year-old man with known rheumatic valvular disease had a mitral commissurotomy 7 years ago. He has moderate mitral stenosis and regurgitation. He is followed in the arrhythmia clinic:

• Right arm-right leg lead reversal – This precludes the interpretation of the limb leads
• Atrial fibrillation with rapid ventricular response (114/min)
• Right bundle branch block

An ECG is recorded 2 days later, with correct lead placement:

• Atrial flutter with variable AV block. Ventricular rate 125/min.
• Left axis deviation
• Right bundle branch block.