A cardiac pacemaker is a device that uses electrical impulses to regulate a normal heartbeat. These electrical impulses are delivered by electrodes to contract the heart muscles. But how did we understand the uses of electrotherapies? It started with Luigi Galvani’s experiment in the 18th century that observed the movement of a dissected frog’s muscles to applied electrical sparks. From that experiment, it was evident that since the heart is a muscle, these electrical sparks could also be applied to it and substitute percussive pacing.
Experiments began in 1788 to attempt to control irregular heartbeats with electric shocks. It wasn’t until 1872 that T. Greene stated that electric shock had the possibility of restarting a stopped heart. A few years layers, Wilhelm von Ziemssen made an important discovery. He discovered that controlled pulses of DC current could accelerate the heart until it matched with the pulses. In 1899, Alexander McWilliam published his experiments that regular heart rhythm could be existent via the applying of regular impulses. This was the foundation and principle upon which the cardiac pacemaker that we know today was built on.
The hymanotor was created. An electromechanical instrument developed by Albert Salisbury Hyman – a New York cardiologist – in 1932, the hymanotor was powered by a spring-wound hand-cranked motor that delivered a regular pulse to the right atrial area of the sinus node via a needle. Hyman was the first to coin the term “artificial pacemaker”. Hyman’s pacemaker was not successful because manufacturers were no interested in it and the medical establishment at that time did not approve of placing the needle into the heart due to difficulty and potential dangers.
In 1950, cardiothoracic surgeons from University of Toronto and Toronto General Hospital worked together with John A. Hopps – an engineer from the Canadian National Research Council – to improve Hyman’s design. Not too long later they developed an AC-powered device using a vacuum-tube that paced the heart from outside the body. In 1952, Paul Maurice Zoll – a Boston cardiologist – improved the pacemaker and kept a man with recurrent cardiac arrest via external stimulation for 52 hours. The main issues with these latest designs were that they were very large, and the patient had to be constrained for it to be in use. In addition, the AC power design meant that the patient had to be plugged into the wall.
Seymour Furman solved one of the problems in 1959 by using a lead passed through a vein to connect the pacemaker to the right ventricle instead of using a needle. This allowed the heart to continue beating during surgery and is known as transvenous pacing. Around the same time, Earl E. Bakken developed the first wearable, battery powered, transistorized pacemaker known as the Medtronic 5800 pacemaker. His pacemaker was the beginning of the liberation of patients from their power-cord arrangements and led the way to prove the safety and effectiveness of pacemaking in the medical field. Medtronic became the industry leader in external pacemaker after being established as a manufacturer of medical devices.
The next challenge was making the pacemaker implantable. This challenge held many problems: the device had to be extremely light, the battery had to be small but long lasting, and the electrical wires had to withstand current while in the body without harming the body. In 1962, Wilson Greatbatch – an engineer – worked with surgeon William C Chardack and developed a power system that allowed patients to live up to 30 years. This system consisted of a two-transistor, transformer-coupled oscillating circuit all powered by a mercury battery.
Several new findings and improvements on the pacemaker came to light as technology advanced. In 1973, Cordis Corporation developed the first implantable pacemaker that could be programmed. In 1982, Dr Anthony Rickards developed the first pacemaker that adapted the heart rate to the body’s demands using sensors and a microprocessor. In 1988, Raul Chirife developed the first responsive pacemaker that can sense blood flow – although it wasn’t ever brought to the commercial market. By 2005, Biventricular pacing for Cardiac Resynchronization Therapy was developed to improve pumping efficiency and control of the heart rhythm.
As technology advanced, all the modes of pacing can be combined into one device that has sensors and control systems to respond to blood flow, concentrations of oxygen and carbon dioxide, and record electrograms that can be analyzed. Today, Tachycardia (rapid heartbeat) is treated with the cardioverter-defibrillator. Soon, smaller and more natural pacemakers are highly probable to be developed. In addition, artificial hearts and tissue engineering is on the rise which may provide another alternative to the pacemaker entirely.