A pacemaker is an electronic device designed to regulate a patient’s heart rhythm, substituting for the heart’s natural electrical system. This small, battery-powered instrument generates electrical pulses that ensure the heart maintains a consistent and functional rate, particularly when dealing with slow, irregular, or blocked heartbeats. The development of this technology represents a profound achievement, transforming the prognosis for millions suffering from cardiac rhythm disorders. Understanding this life-saving invention requires examining the early attempts to harness electricity for cardiac stimulation.
Early Attempts at Electrical Heart Stimulation
The concept of using electricity to influence heart function began long before the modern device emerged. In 1887, scientists demonstrated the ability to record the electrical activity of the human heart, establishing a foundation for understanding the heart’s natural rhythm generator, the sinoatrial (SA) node. This knowledge led to early efforts to artificially stimulate the heart. In 1928, Mark Lidwell reportedly saved a newborn in cardiac arrest by intermittently stimulating the heart electrically.
In the early 1930s, American physician Albert Hyman developed and patented a device he termed the “artificial cardiac pacemaker.” This experimental machine was powered by a spring-wound, hand-cranked motor that generated a direct current. The current was delivered through a needle inserted directly into the heart’s right atrium. Hyman’s device was met with ethical controversy and was not widely accepted by the medical community.
The Invention of the First Practical Pacemaker
The modern era of clinical cardiac pacing began in the early 1950s with the work of Dr. Paul Zoll. In 1952, Zoll developed a large, tabletop external pacemaker that treated heart block by delivering impulses through electrodes placed on the patient’s chest. While life-saving for in-hospital use, this device was powered by alternating current (AC), was bulky, and caused painful skin burns due to the high voltage required.
A significant leap occurred in 1957 when a power failure highlighted the danger of AC-powered devices. This prompted engineer Earl Bakken and surgeon C. Walton Lillehei to create a battery-powered, wearable external pacemaker. Bakken’s transistorized design, housed in a small plastic box, allowed patients limited mobility while providing effective pacing. This portable device, first used clinically in 1958, connected to electrode leads that passed through the skin and attached to the heart’s surface.
The Critical Shift to Implantable Devices
Despite the success of external devices, leads passing through the skin presented a constant risk of infection, necessitating a fully internal system. The first attempt at a fully implantable pacemaker occurred in Stockholm, Sweden, in October 1958. Surgeon Åke Senning and engineer Rune Elmqvist developed a device with a rechargeable battery and implanted it into a patient with complete heart block. Although the initial device failed quickly, the patient received multiple replacements over four decades.
The first commercially produced, self-contained implantable pacemaker was developed in the United States by engineer Wilson Greatbatch and surgeon William Chardack. Implanted in 1960, this device used a long-lasting battery and demonstrated improved reliability. Further advancements focused on lead reliability and long-term power. The development of the lithium-iodide battery in the early 1970s offered a service life of three to five years, eliminating the need for frequent replacements or external recharging.
Anatomy and Function of Contemporary Pacemakers
Modern pacemakers are advanced systems consisting of two main components: the pulse generator and the leads. The pulse generator is a small, sealed titanium box containing the battery and the circuitry necessary to monitor the heart’s activity and generate electrical impulses. The leads are insulated wires that extend from the generator to the heart muscle, delivering the electrical signal and sensing the heart’s natural electrical activity.
Contemporary devices are categorized by the number of chambers they stimulate, such as single-chamber, dual-chamber, or biventricular pacemakers. Dual-chamber pacemakers are common because they use two leads placed in the right atrium and right ventricle, coordinating the contraction of the upper and lower chambers. These devices function “on demand,” delivering a pulse only when the heart rate drops below a preset minimum or when a beat is missed. Newer, leadless pacemakers are miniature devices implanted directly into the heart chamber, eliminating the need for traditional wires entirely.