They go in different places. This device is actually within your left ventrical. In a traditional pacemaker, only the lead is in the ventrical (and another in the atrium possibly) with the device located in a pocket under the collar bone. Traditional pacemakers are explanted when you need a new one. If the leads are still in good shape, the same leads are used with the new pacemaker, so there's no new net increase of volume of product being placed. If the lead isn't useable, then yes, they typically just put in a new one rather than try to extract the old one since explanting them can be risky. After about 3 or 4 leads though, you run out of room.