A cardiac pacemaker is a device thatregulates a normal heartbeat through electrical impulses. These electrical impulsesare delivered by electrodes to contract the heart muscles. But how did we understandthe uses of electrotherapies? It started with Luigi Galvani’s experiment in the18th century that observed the movement of a dissected frog’smuscles to applied electrical sparks. From that experiment, it was evident thatsince the heart is a muscle, these electrical sparks could also be applied toit and substitute percussive pacing. Experimentsbegan 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 possibilityof restarting a stopped heart. A few years layers, Wilhelm von Ziemssen made animportant discovery.
He discovered that controlled pulses of DC current couldaccelerate the heart until it matched with the pulses. In 1899, Alexander McWilliampublished his experiments that regular heart rhythm could be existent via theapplying of regular impulses. This was the foundation and principle upon whichthe cardiac pacemaker that we know today was built on. Thehymanotor was created. An electromechanical instrument developed by AlbertSalisbury Hyman – a New York cardiologist – in 1932, the hymanotor was poweredby a spring-wound hand-cranked motor that delivered a regular pulse to the rightatrial area of the sinus node via a needle.
Hyman was the first to coin theterm “artificial pacemaker”. Hyman’s pacemaker was not successful becausemanufacturers were no interested in it and the medical establishment at that timedid not approve of placing the needle into the heart due to difficulty and potentialdangers. In1950, cardiothoracic surgeons from University of Toronto and Toronto GeneralHospital worked together with John A. Hopps – an engineer from the CanadianNational Research Council – to improve Hyman’s design.
Not too long later theydeveloped an AC-powered device using a vacuum-tube that paced the heart fromoutside the body. In 1952, Paul Maurice Zoll – a Boston cardiologist – improvedthe pacemaker and kept a man with recurrent cardiac arrest via externalstimulation for 52 hours. The main issues with these latest designs were thatthey were very large, and the patient had to be constrained for it to be inuse. In addition, the AC power design meant that the patient had to be pluggedinto the wall. SeymourFurman solved one of the problems in 1959 by using a lead passed through a veinto connect the pacemaker to the right ventricle instead of using a needle. Thisallowed the heart to continue beating during surgery and is known astransvenous pacing.
Around the same time, Earl E. Bakken developed the firstwearable, battery powered, transistorized pacemaker known as the Medtronic 5800pacemaker. His pacemaker was the beginning of the liberation of patients fromtheir power-cord arrangements and led the way to prove the safety andeffectiveness of pacemaking in the medical field.
Medtronic became the industryleader in external pacemaker after being established as a manufacturer ofmedical devices. Thenext challenge was making the pacemaker implantable. This challenge held manyproblems: the device had to be extremely light, the battery had to be small butlong lasting, and the electrical wires had to withstand current while in the bodywithout harming the body. In 1962, Wilson Greatbatch – an engineer – workedwith surgeon William C Chardack and developed a power system that allowedpatients to live up to 30 years.
This system consisted of a two-transistor,transformer-coupled oscillating circuit all powered by a mercury battery. Severalnew findings and improvements on the pacemaker came to light as technologyadvanced. In 1973, Cordis Corporation developed the first implantable pacemakerthat could be programmed. In 1982, Dr Anthony Rickards developed the first pacemakerthat 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 senseblood flow – although it wasn’t ever brought to the commercial market. By 2005,Biventricular pacing for Cardiac Resynchronization Therapy was developed to improvepumping efficiency and control of the heart rhythm. As technologyadvanced, all the modes of pacing can be combined into one device that has sensorsand control systems to respond to blood flow, concentrations of oxygen andcarbon dioxide, and record electrograms that can be analyzed.
Today, Tachycardia(rapid heartbeat) is treated with the cardioverter-defibrillator. Soon, smallerand more natural pacemakers are highly probable to be developed. In addition,artificial hearts and tissue engineering is on the rise which may provideanother alternative to the pacemaker entirely.
