[Pacemaker ECG quiz no. 21: Strange ECG after DDDR pacemaker implantation].

: In a patient with sinus node disease (intermittent sinus arrest with symptomatic pauses >4 s), a DDDR pacemaker with a dedicated algorithm to avoid unnecessary ventricular pacing (mode switch between AAIR and DDDR) was implanted. The pacemaker ECG after implantation shows an unexpected tachycardia.