Parameters Influencing Distal Tip Loading of Pacemaker and Defibrillator Leads

More than 235,000 pacemakers and 130,000 implantable cardioverter defibrillators (ICD) were implanted in the United States in 2009 [1] for the treatment of various cardiac arrhythmias. Traditional pacemakers and ICDs deliver therapy to the patient through a transvenous lead that extends from a subcutaneously-implanted pulse generator, through the subclavian or cephalic vein, the superior vena cava (SVC), and into the heart. Attachment of the distal tip of the lead into the cardiac muscle is accomplished through either an active fixation mechanism where a metal helix is screwed into the cardiac wall at the time of implantation, or a passive fixation mechanism where silicone tines are ensnared by the fibrous trabeculae within the heart. Implantation of both active and passive leads is aided by the insertion of a stylet, or thin wire, into the lead to provide additional stiffness and steerability as the device is pushed through the vasculature and to the implant site.