Pacemakers and implantable cardioverter-defibrillators (ICDs) deliver electrical impulses via wires (called leads) inserted in the heart through a vein. Over time, the leads become covered in scar tissue. If a lead is damaged, disturbed, blocked or infected, or otherwise needs to be removed, it must be very carefully detached from the scar tissue to avoid damaging the surrounding blood vessel or heart muscle. Lead extraction is usually done via a catheter—a flexible tube threaded through the blood vessels—with a tiny laser or drill-like instrument at its tip that helps free the wire from the surrounding tissue. The catheter is normally inserted through an artery in the neck or groin. The pacemaker or ICD may also be removed temporarily as part of the same procedure.