A 76-year-old woman presents with a persistently rapid heart rate that she attributes to her pacemaker. What does the ECG show?

During atrial overdrive pacing at a cycle length of 420 ms, the following EKG was recorded (Fig. 1). What is the mechanism for the progressive widening of QRS complexes and for the normal narrow ...

This ECG shows ventricular pacing ... similar to what occurs in the setting of a left bundle branch block. This right ventricular pacing can induce "ventricular dyssynchrony" which can cause ...

This ECG shows ventricular pacing ... similar to what occurs in the setting of a left bundle branch block. This right ventricular pacing can induce "ventricular dyssynchrony" which can cause ...