A 60-year-old woman is referred to the cardiac clinic because of dyspnea on exertion and tiredness that has been progressing during the past year. She has recently noticed palpitation, that she describes as the sensation of her heart beating irregularly:

• Sinus rhythm with Mobitz I second degree AV block
• Right bundle branch block

The patient was admitted to hospital and investigated. The presence of a dilated cardiomyopathy was demonstrated. The coronary arteries were normal. An AV sequential pacemaker was implanted.