This 81 old patient was implanted years ago for bradycardia associated with permanent AF. He was hospitalized for acute left-sided abdominal pain. Two days after, during the ultrasound examination, he had a cardiac arrest which was treated by 10 min CPR and 2 external shocks. The final diagnosis for the abdominal pain was splenic infarction (subtherapeutic anticoagulation).
The device interrogation revealed a ventricular undersensing resulting in a VF induction by asynchronous pacing. The same day the device had measured a sudden drop in both intrinsic amplitude and impedance associated with a sudden increase in pacing threshold.
No electrolyte perturbation was present and a coronarography excluded any coronary artery stenosis. A new lead was inserted and the patient went home with a new PM.
Asynchronous pacing is a classical although rarely documented cause of life threathening arrhythmia.