Cardiac Pacemakers
Authors: Hutten Helmut 
Published: April 2006

AbstractAn artificial cardiac pacemaker (PM) is a technical assist system either for temporary extracorporeal application or for permanent implantation in order to compensate deficiencies with regard to the regular and rhythmic cardiac activity. This objective is achieved by stimulating the heart with an electrical impulse of sufficient strength. At the beginning, cardiac pacemakers had an exclusively life‐sustaining function. As a consequence of enhanced functional complexity (e.g., rate‐adaptive pacing and multisite pacing), however, they are employed more and more for the improvement of quality of life. A measure for the enhancement of life quality are the gained “Quality‐Adjusted Life‐Years (QALY).” This measure is the arithmetic product of life expectancy and the assessed quality of remaining life‐years. An usual index combines the costs of providing interventions for achieving health‐related quality of life and survival of the patient (i.e., it describes the cost‐utility ratio indicating the costs that are required to generate a year of perfect health (one QALY) and is expressed as costs per QALY). For cardiac pacemakers, this value is at present $1,700/QALY. It is lower than the corresponding value for hip replacement and much lower than the corresponding values for cochlear implants, heart transplantation, or hemodialysis. Cardiac pacemakers are one of the most successful therapeutic devices. Another promising device for the management of cardiac arrhythmias that is using a comparable technology is the defibrillator.All these intelligent stimulating generators result from close interdisciplinary collaboration between medical experts (e.g., cardiology, surgery, physiology), engineers (e.g., electronics, signal processing, informatics, material sciences, production technology, quality control), physicists (e.g., boundary physics, electrochemistry, biophysics, physical measurement methods), and chemists (e.g., battery technology, polymer chemistry). The most relevant requirements for cardiac assist systems are a quasi‐physiological behavior, the near‐perfect compensation of the insufficient cardiac function, high reliability with regard to both the technical components and the functional properties, and simple adjustability to patient‐individual needs. Devices for the management of cardiac arrhythmias are microsystems that use intelligent signal processing for the transformation of sensed information into the adequate control of the activity of the heart (i.e., they are microprocessor‐based, software‐controlled, and multi‐programmable systems). The hardware with its functional options can be compared with a microsystem that contains more than 100,000 transistor functions. Most progress in the recent past has been achieved by enhancing the complexity of signal processing, automatic adjustment of the timing and control regime, development of highly integrated electronic subsystems, reduction in power consumption, diminution of the dimensions of volume and weight, improvement of the electrodes with regard to biocompatibility and efficiency, and enhancement of long‐term reliability.This article about cardiac pacemakers will discuss the fundamentals of cardiac electrophysiology, the principle of cardiac pacing, the most essential properties of the device including the leads and the battery. The following aspects will be not be discussed in depth: (1) the clinical aspects of diagnosis and therapy, (2) the pathophysiological background, (3) the technology employed for the hardware, (4) the processing of the sensed signals including the extraction of parameters for the timing control, (5) special procedures for proper therapy management, and (6) the multitude of company‐specific control algorithms. It is assumed that the readers are familiar with the fundamental engineering knowledge that is not specific for cardiac pacemakers, and that specialized medical knowledge is not required in detail for understanding the basic functions of cardiac pacemakers.