Leads and longevity: how long will your pacemaker last?

Prolonging pacemaker system longevity and time between pulse generator changes remains an important goal of device therapy for several reasons. There is a small but finite risk of infection and other complications each time a generator change is performed. If patients have one less generator change during their lifetime, the relative risk of complications is reduced. A 10% increase in generator longevity will result in large savings for healthcare costs each year. Therefore, interest in maximizing pacemaker longevity continues. Modern pacemakers use current not only for pacing but also for other functions such as obtaining measurements of diagnostic data, measurements made by rate response sensors, and implementation of algorithms, such as for mode switching. Pacemaker battery life therefore depends on a variety of variables, including baseline battery self-discharge, current drain for device housekeeping functions, current used to pace the heart, and current to sense the underlying heart rhythm. An average pacemaker battery has about 0.5–2Ah of battery life. Factors controlling current drain with a pacing stimulus include pacing rate, per cent pacing, programmed voltage, pulse width (PW), and lead impedance. Energy use is proportional to PW and to the square of the voltage. By Ohms law, I = V / R , where R is the impedance, current is inversely proportional to impedance. For a given voltage ( V ) and PW, current will be less for a high-impedance lead. For an electrical circuit, a voltage drop occurs and energy is dissipated across a load or impedance. The area of high impedance in a lead should … *Corresponding author. Tel: +1 804 828 7565, Fax: +1 804 828 6082. Email: rshepard{at}mcvh-vcu.edu