Incessant atrioventricular dissociation due to far-field QRS oversensing and recurrent mode switch in a dual chamber pacemaker.

We report the case of a repetitive and incessant activation of mode switch in a dual chamber pacemaker because of the inappropriate sensing by the atrial lead of far-fields signals from the ventricular evoked response. The incidence, consequences and prevention of the oversensing of far-field QRS complexes are discussed.