A 58-year-old man is being monitored in the cardiac surgical ward 5 days after replacement of his aortic valve because of severe aortic regurgitation, when he developed palpitation and dyspnea:

Atrial fibrillation with rapid ventricular response (195/min)

• One premature ventricular complex
• Left bundle branch block

ECG 2 is recorded when the arrhythmia subsided:

• Sinus rhythm
• Left bundle branch block