This was a very elderly woman with a pacemaker and minimal symptoms:

What are these broad complexes superimposed on the native QRS?  Are they paced?

These cannot be anything other than artifact.

Although they are regular, and appear in every lead, they occur during the ventricular refractory period during beats 1, 2, 3, and 4, and these ones also are identical to those which are between ventricular beats.

I do not know what was causing this.