A
pacemaker (or
artificial pacemaker, so as not to be confused with the heart's natural
pacemakerThe contractions of the heart are controlled by chemical impulses. The rate these impulses fire controls the heart rate.The cells that create these rhythmical impulses are called pacemaker cells, and they directly control the heart rate...
) is a
medical deviceA medical device is a product which is used for medical purposes in patients, in diagnosis, therapy or surgery. If applied to the body, the effect of the medical device is primarily physical, in contrast to pharmaceutical drugs, which exert a biochemical effect. Specific regional definitions of...
which uses electrical impulses, delivered by
electrodeAn electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...
s contacting the heart muscles, to regulate the beating of the
heartThe heart is a muscular organ found in all vertebrates that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
. The primary purpose of a pacemaker is to maintain an adequate
heart rateHeart rate is determined by the number of heartbeats per unit of time, typically expressed as beats per minute , it can vary with as the body's need for oxygen changes, such as during exercise or sleep. The measurement of heart rate is used by medical professionals to assist in the diagnosis and...
, either because the heart's
native pacemakerThe sinoatrial node is the impulse-generating tissue located in the right atrium of the heart, and thus the generator of sinus rhythm. It is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava...
is not fast enough, or there is a block in the
heart's electrical conduction systemThe normal electrical conduction in the heart allows the impulse that is generated by the sinoatrial node of the heart to be propagated to the myocardium . The myocardium contracts after stimulation...
. Modern pacemakers are externally programmable and allow the cardiologist to select the optimum pacing modes for individual patients. Some combine a pacemaker and
defibrillatorAn implantable cardioverter-defibrillator is a small battery-powered electrical impulse generator which is implanted in patients who are at risk of sudden cardiac death due to ventricular fibrillation. The device is programmed to detect cardiac arrhythmia and correct it by delivering a jolt of...
in a single implantable device. Others have multiple electrodes stimulating differing positions within the heart to improve
synchronisationSynchronization or synchronisation is timekeeping which requires the coordination of events to operate a system in unison. The familiar conductor of an orchestra serves to keep the orchestra in time....
of the
lower chambersIn the heart, a ventricle is a heart chamber which collects blood from an atrium and pumps it out of the heart...
of the heart.
History
In 1889, J A McWilliam reported in the British Medical Journal of his experiments in which application of an electrical impulse to the human heart in
asystoleIn medicine, asystole is a state of no cardiac electrical activity, hence no contractions of the myocardium and no cardiac output or blood flow...
caused a ventricular contraction and that a heart rhythm of 60-70 beats per minute could be evoked by impulses applied at spacings equal to 60-70/minute.
In 1926, Dr Mark C Lidwell of the
Royal Prince Alfred HospitalThe Royal Prince Alfred Hospital is a major public teaching hospital in Sydney, Australia, located on Missenden Road in Camperdown...
of Sydney, supported by physicist Edgar H Booth of the
University of SydneyThe University of Sydney is the oldest university in Australia. It was established in Sydney in 1850. It is a member of Australia's "Group of Eight" universities that are highly ranked in terms of their research performance...
, devised a portable apparatus which "plugged into a lighting point" and in which "One pole was applied to a skin pad soaked in strong salt solution" while the other pole "consisted of a needle insulated except at its point, and was plunged into the appropriate cardiac chamber". "The pacemaker rate was variable from about 80 to 120 pulses per minute, and likewise the voltage variable from 1.5 to 120 volts" In 1928, the apparatus was used to revive a stillborn infant at
Crown Street Women's Hospital, SydneyCrown Street Women's Hospital was once the largest maternity hospital in Sydney, New South Wales, Australia. It was located in Crown Street, Surry Hills....
whose heart continued "to beat on its own accord", "at the end of 10 minutes" of stimulation.
In 1932, American physiologist
Albert HymanAlbert S. Hyman , a New York cardiologist, together with his brother Charles, constructed in 1930-1932 an electro-mechanical device which was one of the earliest artificial pacemakers...
, working independently, described an electro-mechanical instrument of his own, powered by a spring-wound hand-cranked motor. Hyman himself referred to his invention as an "artificial pacemaker", the term continuing in use to this day.
An apparent hiatus in publication of research conducted between the early 1930s and
World War IIWorld War II, or the Second World War , was a global military conflict which involved a majority of the world's nations, including all great powers, organized into two opposing military alliances: the Allies and the Axis...
may be attributed to the public perception of interfering with nature by 'reviving the dead'. For example, "Hyman did not publish data on the use of his pacemaker in humans because of adverse publicity, both among his fellow physicians, and due to newspaper reporting at the time. Lidwell may have been aware of this and did not proceed with his experiments in humans".
An external pacemaker was designed and built by the Canadian electrical engineer
John HoppsJohn Alexander "Jack" Hopps Canadian, was one of the pioneers of the artificial pacemaker and is known as the "father of biomedical engineering in Canada"....
in 1950 based upon observations by cardio-thoracic surgeon Wilfred Gordon Bigelow at
Toronto General HospitalThe Toronto General Hospital , is a part of the University Health Network, and a major teaching hospital in downtown Toronto, Ontario. It is located in the Discovery District, directly north of the Hospital for Sick Children, across Gerrard Street West, and east of Princess Margaret Hospital and...
. A substantial external device using
vacuum tubeIn electronics, a vacuum tube, electron tube , thermionic valve, or valve is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space...
technology to provide
transcutaneous pacingTranscutaneous pacing is a temporary means of pacing a patient's heart during a medical emergency. It is accomplished by delivering pulses of electric current through the patient's chest, which stimulates the heart to contract....
, it was somewhat crude and painful to the patient in use and, being powered from an AC wall socket, carried a potential hazard of
electrocutionAn electric shock can occur upon contact of a human body with any source of voltage high enough to cause sufficient current through the muscles or hair. The minimum current a human can feel is thought to be about 1 milliampere ....
of the patient by inducing
ventricular fibrillationVentricular fibrillation is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart, making them tremble rather than contract properly...
.
A number of innovators, including
Paul ZollPaul Maurice Zoll is a cardiologist and was one of the pioneers in the development of the cardiac pacemaker and cardiac defibrillat.Biography...
, made smaller but still bulky
transcutaneous pacingTranscutaneous pacing is a temporary means of pacing a patient's heart during a medical emergency. It is accomplished by delivering pulses of electric current through the patient's chest, which stimulates the heart to contract....
devices in the following years using a large rechargeable battery as the power supply.
In 1957, Dr. William L. Weirich published the results of research performed at the
University of MinnesotaThe University of Minnesota, Twin Cities is a public research university located in Minneapolis and St. Paul, Minnesota, United States...
. These studies demonstrated the restoration of heart rate, cardiac output and mean aortic pressures in animal subjects with complete
heart blockA heart block is a disease in the electrical system of the heart. This is opposed to coronary artery disease, which is disease of the blood vessels of the heart...
through the use of a myocardial electrode. This effective control of postsurgical heart block proved to be a significant contribution to decreasing
mortalityDeath is the termination of the biological functions that define a living organism. It refers to both a particular event and to the condition that results thereby. The true nature of the latter has for millennia been a central concern of the world's religious traditions and of philosophical...
of
open heart surgeryOpen Heart Surgery was released on August 8, 2000 by rock band Virginwool. The band signed to Breaking/Atlantic Records after initially beginning signed to Universal Records. The album was produced and mixed by Brad Wood....
in this time period.
The development of the
siliconSilicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. A tetravalent metalloid, silicon is less reactive than its chemical analog carbon...
transistorA transistor is a semiconductor device commonly used to amplify or switch electronic signals. A transistor is made of a solid piece of a semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's...
and its first commercial availability in 1956 was the pivotal event which led to rapid development of practical cardiac pacemaking.
In 1957, engineer
Earl BakkenEarl E. Bakken is an American engineer, businessman and philanthropist of Norwegian American ancestry...
of Minneapolis, Minnesota, produced the first wearable external pacemaker for a patient of Dr.
C. Walton LilleheiClarence Walton Lillehei , was an American surgeon who pioneered open-heart surgery, as well as numerous techniques, equipment and prostheses for cardiothoracic surgery.-Biography:...
. This transistorised pacemaker, housed in a small plastic box, had controls to permit adjustment of pacing heart rate and output voltage and was connected to electrode leads which passed through the skin of the patient to terminate in electrodes attached to the surface of the myocardium of the heart.
The first clinical implantation into a human of a fully implantable pacemaker was in 1958 at the Karolinska Institute in Solna, Sweden, using a pacemaker designed by
Rune ElmqvistRune Elmqvist developed the first implantable pacemaker in 1958, working under the direction of Åke Senning, senior physician and cardiac surgeon at the Karolinska University Hospital in Solna, Sweden....
and surgeon
Åke SenningÅke Senning was a pioneering Swedish cardiac surgeon, who implanted the first implantable pacemaker, invented the Senning operation, and contributed to many other advances....
, connected to electrodes attached to the myocardium of the heart by
thoracotomyThoracotomy is an incision into the pleural space of the chest. It is performed by a surgeon, and, rarely, by emergency physicians, to gain access to the thoracic organs, most commonly the heart, the lungs, the esophagus or thoracic aorta, or for access to the anterior spine such as is necessary...
. The device failed after three hours. A second device was then implanted which lasted for two days. The world's first implantable pacemaker patient, Arne Larsson, went on to receive 26 different pacemakers during his lifetime. He died in 2001, at the age of 86.
In 1959, temporary
transvenous pacingTemporary transvenous cardiac pacing, also called endocardial pacing, is a potentially life saving intervention used primarily to correct profound bradycardia. It can be used to treat symptomatic bradycardias that do not respond to transcutaneous pacing or to drug therapy...
was first demonstrated by Furman
et al. in which the
catheterIn medicine a catheter is a tube that can be inserted into a body cavity, duct or vessel. Catheters thereby allow drainage, injection of fluids or access by surgical instruments. The process of inserting a catheter is catheterization. In most uses a catheter is a thin, flexible tube , although...
electrode was inserted via the patient's
basilic veinIn human anatomy, the basilic vein is a large superficial vein of the upper limb that helps drain parts of hand and forearm. It originates on the medial side of the dorsal venous network of the hand, and it travels up the base of the forearm and arm...
.
In February 1960, an improved version of the Swedish Elmqvist design was implanted in
MontevideoMontevideo is the largest city, the capital and chief port of Uruguay. Montevideo is the only city in the country with a population over 1,000,000...
,
UruguayUruguay , is a country located in the southeastern part of South America. It is home to 3.46 million people, of whom 1.1 million live in the capital Montevideo and its metropolitan area. An estimated 88–94% of the population are of mostly European and/or mixed descent.Uruguay's only land border is...
in the Casmu Hospital by Doctors Fiandra and Rubio. That device lasted until the patient died of other ailments, 9 months later. The early Swedish-designed devices used rechargeable batteries, which were charged by an induction coil from the outside.
Implantable pacemakers constructed by engineer
Wilson GreatbatchWilson Greatbatch is an engineer and inventor who advanced the development of early implantable cardiac pacemakers. He is a graduate of Cornell University and the University at Buffalo...
entered use in humans from April 1960 following extensive
animal testingAnimal testing, also known as animal experimentation, animal research, and in vivo testing, is the use of non-human animals in experiments. It is estimated that 50 to 100 million vertebrate animals worldwide — from zebrafish to non-human primates — are used annually...
. The Greatbatch innovation varied from the earlier Swedish devices in using primary cells (
mercury batteryA mercury battery is a non-rechargeable electrochemical battery, a primary cell. Due to the content of mercury, and the resulting environmental concerns, the sale of mercury batteries is banned in many countries. Both ANSI and IEC have withdrawn standards for mercury batteries...
) as the energy source. The first patient lived for a further 18 months.
The first use of
transvenous pacingTemporary transvenous cardiac pacing, also called endocardial pacing, is a potentially life saving intervention used primarily to correct profound bradycardia. It can be used to treat symptomatic bradycardias that do not respond to transcutaneous pacing or to drug therapy...
in conjunction with an implanted pacemaker was by Parsonnet in the USA , Lagergren in Sweden and Jean-Jaques Welti in France in 1962-63.
The transvenous, or pervenous, procedure involved incision of a vein into which was inserted the
catheterIn medicine a catheter is a tube that can be inserted into a body cavity, duct or vessel. Catheters thereby allow drainage, injection of fluids or access by surgical instruments. The process of inserting a catheter is catheterization. In most uses a catheter is a thin, flexible tube , although...
electrode lead under fluoroscopic guidance, until it was lodged within the trabeculae of the right ventricle. This method was to become the method of choice by the mid-1960s.
The preceding implantable devices all suffered from the unreliability and short lifetime of the available primary cell technology which was mainly that of the
mercury batteryA mercury battery is a non-rechargeable electrochemical battery, a primary cell. Due to the content of mercury, and the resulting environmental concerns, the sale of mercury batteries is banned in many countries. Both ANSI and IEC have withdrawn standards for mercury batteries...
.
In the late 1960s, several companies, including ARCO in the USA, developed isotope powered pacemakers, but this development was overtaken by the development in 1970 of the lithium-iodide cell by
Wilson GreatbatchWilson Greatbatch is an engineer and inventor who advanced the development of early implantable cardiac pacemakers. He is a graduate of Cornell University and the University at Buffalo...
. Lithium-iodide or lithium anode cells became the standard for future pacemaker designs.
A further impediment to reliability of the early devices was the diffusion of water vapour from the body fluids through the
epoxyEpoxy or polyepoxide is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives.- Chemistry :...
resin encapsulation affecting the electronic circuitry. This phenomenon was overcome by encasing the pacemaker generator in an hermetically sealed metal case, initially by
TelectronicsTelectronics Pty Ltd was an Australian company best known for its role in developing the pacemaker. In 1988 the business was acquired by Pacific Dunlop...
of Australia in 1969 followed by Cardiac Pacemakers Inc of Minneapolis in 1972. This technology, using titanium as the encasing metal, became the standard by the mid-1970s.
Others who contributed significantly to the technological development of the pacemaker in the pioneering years were Bob Anderson of
MedtronicMedtronic, Inc. , based in Minneapolis, Minnesota, is the world's largest medical technology company. Listed among Fortune 500 companies, Medtronic is a publicly traded company and is listed on the New York Stock Exchange under the symbol MDT...
Minneapolis, J.G (Geoffrey) Davies of
St George's HospitalSt George's Hospital, founded in 1733, is a teaching hospital in London, England. It has continuously trained medical students since that date.-History:...
London,
Barouh BerkovitsBarouh Berkovits is one of the pioneers of Bio-engineering; particularly the cardiac defibrillator and artificial cardiac pacemaker.-External links:*http://www.hrsonline.org/ep-history/notable_figures/bios/barouh_berkovits/...
and Sheldon Thaler of American Optical,
Geoffrey WickhamGeoffrey Gordon Wickham AO MIIE was one of the pioneers of cardiac pacemaking, born at Camperdown, Victoria, Australia to dairy farmer parents on October 28th 1933.In 1963 he co-founded the medical instruments company Telectronics Pty Ltd in Sydney , and served as the company's Technical Director...
of
TelectronicsTelectronics Pty Ltd was an Australian company best known for its role in developing the pacemaker. In 1988 the business was acquired by Pacific Dunlop...
Australia,
Walter KellerWalter Keller is a mathematician, physicist, researcher, designer, and inventor. He designed and holds the patent on the first implantable atrial synchronous heart pacemaker; he designed a demand circuit critical to the controls of the artificial heart; and he pioneered the first remotely...
of
CordisCordis may refer to:* Cordis , a medical device company owned by Johnson & Johnson* Community Research & Development Information Service...
Corp. of Miami,
Hans ThornanderHans Thornander cardiac pacemaker history. One of the pioneers of cardiac pacemaking....
who joined previously mentioned Rune Elmquist of Elema-Schonander in Sweden,
Janwillem van den BergJanwillem van den Berg was a Dutch speech scientist and medical physicist who played a major role in establishing the myoelastic-aerodynamic theory of voice production...
of Holland and
Anthony AdducciAnthony J. Adducci was a pioneer of the medical device industry in Minnesota. He is best known for co-founding Guidant Corp. precursor Cardiac Pacemakers, inc., now part of Boston Scientific, the company that manufactured the world's first lithium battery powered artificial pacemaker.- Early life...
of Cardiac Pacemakers Inc.
GuidantGuidant Corporation, part of Boston Scientific, designs and manufactures artificial pacemakers, implantable defibrillators, stents, and other cardiovascular medical products. Their company headquarters is located in Indianapolis, Indiana. Their main competitors are Medtronic, St. Jude Medical,...
Percussive Pacing
Percussive Pacing, also known as Transthoracic Mechanical Pacing, is the use of the closed fist, usually on the left lower edge of the sternum over the right ventricle in the vena cava, striking from a distance of 20 - 30 cm to induce a ventricular beat (the British Journal of Anesthesia suggests this must be done to raise the ventricular pressure to 10 - 15mmhg to induce electrical activity). This is an old procedure used only as a life saving means until an electrical pacemaker is brought to the patient.
Transcutaneous Pacing
Transcutaneous pacing (TCP), also called external pacing, is recommended for the initial stabilization of hemodynamically significant
bradycardiaBradycardia , as applied to adult medicine, is defined as a resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min....
s of all types. The procedure is performed by placing two pacing pads on the patient's chest, either in the anterior/lateral position or the anterior/posterior position. The rescuer selects the pacing rate, and gradually increases the pacing current (measured in mA) until electrical capture (characterized by a wide QRS complex with a tall, broad T wave on the
ECGElectrocardiography is a transthoracic interpretation of the electrical activity of the heart over time captured and externally recorded by skin electrodes. It is a noninvasive recording produced by an electrocardiographic device...
) is achieved, with a corresponding pulse. Pacing artifact on the
ECGElectrocardiography is a transthoracic interpretation of the electrical activity of the heart over time captured and externally recorded by skin electrodes. It is a noninvasive recording produced by an electrocardiographic device...
and severe muscle twitching may make this determination difficult. External pacing should not be relied upon for an extended period of time. It is an emergency procedure that acts as a bridge until transvenous pacing or other therapies can be applied.
Epicardial Pacing (temporary)
Temporary epicardial pacing is used during open heart surgery should the surgical procedure create atrio ventricular block. The electrodes are placed in contact with the outer wall of the ventricle (epicardium) to maintain satisfactory cardiac output until a temporary transvenous electrode has been inserted.
Transvenous Pacing (temporary)
Transvenous pacing, when used for temporary pacing, is an alternative to transcutaneous pacing. A pacemaker wire is placed into a vein, under sterile conditions, and then passed into either the right atrium or right ventricle. The pacing wire is then connected to an external pacemaker outside the body. Transvenous pacing is often used as a bridge to permanent pacemaker placement. It can be kept in place until a permanent pacemaker is implanted or until there is no longer a need for a pacemaker and then it is removed.
Permanent pacing
Permanent pacing with an implantable pacemaker involves transvenous placement of one or more pacing electrodes within a chamber, or chambers, of the heart. The procedure is performed by incision of a suitable vein into which the electrode lead is inserted and passed along the vein, through the valve of the heart, until positioned in the chamber. The procedure is facilitated by
fluoroscopyFluoroscopy is an imaging technique commonly used by physicians to obtain real-time moving images of the internal structures of a patient through the use of a fluoroscope. In its simplest form, a fluoroscope consists of an x-ray source and fluorescent screen between which a patient is placed...
which enables the physician or cardiologist to view the passage of the electrode lead. After satisfactory lodgement of the electrode is confirmed the opposite end of the electrode lead is connected to the pacemaker generator.
There are three basic types of permanent pacemakers, classified according to the number of
chambersHeart chamber is a general term used to refer to any of the four chambers of the mammalian heart :*Right atrium: receives oxygen-depleted blood from the body via the superior vena cava and the inferior vena cava and pumps it through the tricuspid valve into the right ventricle.*Right ventricle:...
involved and their basic operating mechanism:
- Single-chamber pacemaker. In this type, only one pacing lead is placed into a chamber of the heart, either the atrium
Atrium may refer to:*Atrium , a large open space within a building*Atrium , microscopic air sacs in lungs*Atrium , an anatomical structure of the heart* Atrium of the ventricular system of the brain...
or the ventricleVentricle may refer to:* Ventricle , the pumping chambers of the heart* Ventricular system in the brain* Ventricle of the larynx, a structure in the larynx...
.
- Dual-chamber pacemaker. Here, wires are placed in two chambers of the heart. One lead paces the atrium and one paces the ventricle. This type more closely resembles the natural pacing of the heart by assisting the heart in coordinating the function between the atria and ventricles.
- Rate-responsive pacemaker. This pacemaker has sensors that detect changes in the patient's physical activity and automatically adjust the pacing rate to fulfill the body's metabolic needs.
The pacemaker generator is a hermetically sealed device containing a power source, usually a
lithium batteryLithium batteries are disposable batteries that have lithium metal or lithium compounds as an anode. Depending on the design and chemical compounds used, lithium cells can produce voltages from 1.5 V to about 3.7 V, up to twice the voltage of an ordinary zinc-carbon battery or alkaline cell...
, a sensing amplifier which processes the electrical manifestation of naturally occurring heart beats as sensed by the heart electrodes, the
computerA computer is a machine that manipulates data according to a set of instructions.Although mechanical examples of computers have existed through much of recorded human history, the first electronic computers were developed in the mid-20th century . These were the size of a large room, consuming as...
logic for the pacemaker and the output circuitry which delivers the pacing impulse to the electrodes.
Most commonly, the generator is placed below the subcutaneous fat of the chest wall, above the muscles and bones of the chest. However, the placement may vary on a case by case basis.
The outer casing of pacemakers is so designed that it will rarely be rejected by the body's
immune systemAn immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumour cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
. It is usually made of
titaniumTitanium is a chemical element with the symbol Ti and atomic number 22. Sometimes called the “space age metal”, it has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color.Titanium can be alloyed with iron, aluminium, vanadium, molybdenum, among other...
, which is inert in the body. The whole thing will not be rejected, and will be encapsulated by
scar tissueScar tissue can refer to:*Granulation tissue, a product of healing in major wounds*The tissue of a scar*"Scar Tissue", a Red Hot Chili Peppers song*Scar Tissue , the autobiography of Anthony Kiedis, lead singer of the Red Hot Chili Peppers...
, in the same way a piercing is.
Basic function
Modern pacemakers usually have multiple functions. The most basic form monitors the heart's native electrical rhythm. When the pacemaker fails to sense a heartbeat within a normal beat-to-beat time period, it will stimulate the ventricle of the heart with a short low voltage pulse. This sensing and stimulating activity continues on a beat by beat basis.
The more complex forms include the ability to sense and/or stimulate both the atrial and ventricular chambers.
The revised NASPE/BPEG generic code for antibradycardia pacing
| I |
II |
III |
IV |
V |
| Chamber(s) paced |
Chamber(s) sensed |
Response to sensing |
Rate modulation |
Multisite pacing |
| O = None |
O = None |
O = None |
O = None |
O = None |
| A = Atrium |
A = Atrium |
T = Triggered |
R = Rate modulation |
A = Atrium |
| V = Ventricle |
V = Ventricle |
I = Inhibited |
|
V = Ventricle |
| D = Dual (A+V) |
D = Dual (A+V) |
D = Dual (T+I) |
|
D = Dual (A+V) |
From this the basic ventricular "on demand" pacing mode is VVI or with automatic rate adjustment for exercise VVIR - this mode is suitable when no synchronization with the atrial beat is required, as in atrial fibrillation. The equivalent atrial pacing mode is AAI or AAIR which is the mode of choice when atrioventricular conduction is intact but the natural pacemaker the
sinoatrial nodeThe sinoatrial node is the impulse-generating tissue located in the right atrium of the heart, and thus the generator of sinus rhythm. It is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava...
is unreliable - sinus node disease (SND) or
sick sinus syndromeSick sinus syndrome, also called sinus node dysfunction, is a group of abnormal heart rhythms presumably caused by a malfunction of the sinus node, the heart's primary pacemaker...
. Where the problem is
atrioventricular blockAn atrioventricular block involves the impairment of the conduction between the atria and ventricles of the heart. Strong vagal stimulation may produce AV block...
(AVB) the pacemaker is required to detect ("sense") the atrial beat and after a normal delay (0.1-0.2 seconds) trigger a ventricular beat, unless it has already happened - this is VDD mode and can be achieved with a single pacing lead with electrodes in the right atrium (to sense) and ventricle (to sense and pace). These modes AAIR and VDD are unusual in the US but widely used in Latin America and Europe. The DDDR mode is most commonly used as it covers all the options though the pacemakers require separate atrial and ventricular leads and are more complex, requiring careful programming of their functions for optimal results.
Biventricular Pacing (BVP)
A biventricular pacemaker, also known as CRT (cardiac resynchronization therapy) is a type of pacemaker that can pace both the septal and lateral walls of the left ventricle. By pacing both sides of the left ventricle, the pacemaker can resynchronize a heart whose opposing walls do not contract in synchrony, which occurs in approximately 25-50 % of heart failure patients.
CRT devices have at least two leads, one in the right ventricle to stimulate the septum, and another inserted through the
coronary sinusThe coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the myocardium of the heart. It is present in humans and other animals....
to pace the lateral wall of the left ventricle. Often, for patients in normal sinus rhythm, there is also a lead in the right atrium to facilitate synchrony with the atrial contraction. Thus, timing between the atrial and ventricular contractions, as well as between the septal and lateral walls of the left ventricle can be adjusted to achieve optimal cardiac function.
CRT devices have been shown to reduce mortality and improve quality of life in patients with heart failure symptoms; a LV ejection fraction less than or equal to 35% and QRS duration on EKG of 120 msec or greater. CRT can be combined with an
implantable cardioverter-defibrillatorAn implantable cardioverter-defibrillator is a small battery-powered electrical impulse generator which is implanted in patients who are at risk of sudden cardiac death due to ventricular fibrillation. The device is programmed to detect cardiac arrhythmia and correct it by delivering a jolt of...
(ICD).
Advancements in function
A major step forward in pacemaker function has been to attempt to mimic nature by utilizing various inputs to produce a rate-responsive pacemaker using parameters such as the
QT intervalIn medicine, specifically cardiology, the QT interval is a measure of the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle.-Calculation:...
, pCO - pCO2 (dissolved
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
or
carbon dioxideCarbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
levels) in the arterial-venous system, physical activity as determined by an
accelerometerAn accelerometer measures the acceleration it experiences relative to freefall.Single- and multi-axis models are available to detect magnitude and direction of the acceleration as a vector quantity, and can be used to sense orientation, vibration and shock...
, body temperature,
ATP- Chemistry and biochemistry :* Adenosine triphosphate, the main energy storage and transfer molecule in the cell* Alberta Taciuk Process, a hydrocarbons dry retorting technology- Companies :* Alberta Theatre Projects, a major Canadian theatre company....
levels, adrenaline, etc.
Instead of producing a static, predetermined heart rate, or intermittent control, such a pacemaker, a 'Dynamic Pacemaker', could compensate for both actual respiratory loading and potentially anticipated respiratory loading. The first dynamic pacemaker was invented by Dr. Anthony Rickards of the National Health Hospital, London, UK, in 1982. .
Dynamic Pacemaking technology could also be applied to future artificial hearts. Advances in transitional tissue welding would support this and other artificial organ/joint/tissue replacement efforts.
Stem cells may or may not be of interest to transitional tissue welding.
Many advancements have been made to enhance the control of the pacemaker once implanted. Many of these enhancements have been made possible by the transition to microprocessor controlled pacemakers. Pacemakers that control not only the ventricles but the atria as well have become common. Pacemakers that control both the atria and ventricles are called dual-chamber pacemakers. Although these dual-chamber models are usually more expensive, timing the contractions of the atria to precede that of the ventricles improves the pumping efficiency of the heart and can be useful in congestive heart failure.
Rate responsive pacing allows the device to sense the physical activity of the patient and respond appropriately by increasing or decreasing the base pacing rate via rate response algorithms.
The DAVID trials have shown that unnecessary pacing of the right ventricle can lead to heart failure and an increased incidence of atrial fibrillation. The newer dual chamber devices can keep the amount of right ventricle pacing to a minimum and thus prevent worsening of the heart disease.
Insertion
A pacemaker is typically inserted into the patient through a simple surgery using either
local anestheticA local anesthetic is a drug that causes reversible local anesthesia and a loss of nociception. When it is used on specific nerve pathways , effects such as analgesia and paralysis can be achieved....
or a general anesthetic. The patient may be given a drug for relaxation before the surgery as well. An antibiotic is typically administered to prevent infection. In most cases the pacemaker is inserted in the left shoulder area where an incision is made below the collar bone creating a small pocket where the pacemaker is actually housed in the patient's body. The lead or leads (the number of leads varies depending on the type of pacemaker) are fed into the heart through a large vein using a fluoroscope to monitor the progress of lead insertion. A temporary drain may be installed and removed the following day. The actual surgery may take about an hour.
Following surgery the patient should exercise reasonable care about the wound as it heals. There is a followup session during which the pacemaker is checked using a "programmer" that can communicate with the device and allows a health care professional to evaluate the system's integrity and determine the settings such as pacing voltage output.
The patient may want to consider some basic preparation before the surgery. The most basic preparation is that people who have body hair on the chest may want to remove the hair by shaving or using a depilatory agent as the surgery will involve bandages and monitoring equipment to be afixed to the body.
Since a pacemaker uses batteries, the device itself will need replacement as the batteries lose power. Device replacement is usually a simpler procedure than the original insertion as it does not normally require leads to be implanted. The typical replacement requires a surgery in which an incision is made to remove the existing device, the leads are removed from the existing device, the leads are attached to the new device, and the new device is inserted into the patient's body replacing the previous device.
Pacemaker Patient Identification Card
International Pacemaker Patient Identification Cards carry information such as; patient data (between others, symptom primary, ECG, aetiology), pacemaker center (doctor, hospital),
IPGIPG may refer to:*Interactive program guide, another name for an electronic program guide, a graphical user interface for cable tv boxes, satellite tv boxes, VCRs, DVRs and televisions which displays programming information...
(
rateIn mathematics, a rate is a ratio between two measurements, often with different units.. If the unit or quantity in respect of which something is changing is not specified, usually the rate is per unit time. However, a rate of change can be specified per unit time, or per unit of length or mass...
,
modeMode may mean:* Mode * Mode , the value that has the largest number of observations* Musical mode, a classification system of musical tonalities...
, date of implantation,
MFGMFG can refer to:* Mizuho Financial Group's ticker symbol on the New York Stock Exchange* MFG.com, an online marketplace serving the global manufacturing community* Message From God, a psychedelic trance project from Israel...
,
typeType may refer to:In philosophy:*A type is a category of being*Type-token distinctionIn mathematics:*Type *Type theory, basis for the study of type systems*Type or Arity, the number of operands a function takes...
) and
leadLead is a main-group element with symbol Pb and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metals. Lead has a bluish-white color when freshly cut, but tarnishes to a dull grayish color when exposed to air...
.
Periodic Pacemaker Checkups
Once the pacemaker is implanted, it is periodically checked to ensure the device is operational and performing appropriately. Depending on the frequency set by the following physician, the device can be checked as often as is necessary. Routine pacemaker checks are typically done in-office every six (6) months, though will vary depending upon patient/device status and remote monitoring availability.
At the time of in-office follow-up, the device will be interrogated to perform diagnostic testing. These tests include:
- Sensing: the ability of the device to "see" intrinsic cardiac activity (Atrial and ventricular depolarization).
- Impedance: A test to measure lead integrity. Large and/or sudden increases in impedance can be indicative of a lead fracture while large and/or sudden decreases in impedance can signify a breach in lead insulation.
- Threshold: this test confirms the minimum amount of energy (Both volts and pulse width) required to reliably depolarize (capture) the chamber being tested. Determining the threshold allows the Allied Professional, Representative, or Physician to program an output that recognizes an appropriate safety margin while optimizing device longevity.
As modern pacemakers are "on-demand", meaning that they only pace when necessary, device longevity is affected by how much it is utilized. Other factors affecting device longevity include programmed output and algorithms (features) causing a higher level of current drain from the battery.
An additional aspect of the in-office check is to examine any events that were stored since the last follow-up. These are typically stored based on specific criteria set by the physician and specific to the patient. Some devices have the availability to display intracardiac electrograms of the onset of the event as well as the event itself. This is especially helpful in diagnosing the cause or origin of the event and making any necessary programming changes.
Lifestyle Considerations
A patient's lifestyle is usually not modified to any great degree after insertion of a pacemaker. There are a few activities that are unwise such as full contact sports and activities that involve intense magnetic fields.
The pacemaker patient may find that some types of everyday actions need to be modified. For instance, the shoulder harness of a vehicle seatbelt may be uncomfortable if the harness should fall across the pacemaker insertion site.
Any kind of an activity that involves intense magnetic fields should be avoided. This includes activities such as
arc weldingArc welding uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. They can use either direct or alternating current, and consumable or non-consumable electrodes...
possibly, with certain types of equipment, or maintaining heavy equipment that may generate intense magnetic fields (such as an MRI (Magnetic Resonance Imaging Machine)).
A 2008 U.S. study has found that the magnets in some portable music player headphones may interfere with pacemakers when placed in close proximity.
Some medical procedures may require the use of
antibioticIn common usage, an antibiotic is a substance or compound that kills or inhibits the growth of bacteria...
s to be administered before the procedure. The patient should inform all medical personnel that they have a pacemaker. Some standard medical procedures such as the use of
Magnetic resonance imagingMagnetic Resonance Imaging , or nuclear magnetic resonance imaging , is primarily a medical imaging technique most commonly used in radiology to visualize the internal structure and function of the body...
(MRI) may be ruled out by the patient having a pacemaker.
In addition, according to the American Heart Association, there are other devices that cause risk with patients that have pacemakers, such as:
• anti-theft systems which are also known as electronic article surveillance (EAS)
• metal detectors for security
• cell phones
• extracorporeal shock-wave lithotripsy (ESWL)
• radiofrequency ablation (RFA)
• short-wave or microwave diathermy
• therapeutic radiation
• transcutaneous electric nerve stimulation (TENS)
Privacy and security
Security and privacy concerns have been raised with pacemakers that allow wireless communication. Unauthorized third parties may be able to read patient records contained in the pacemaker, or reprogram the devices, as has been demonstrated by a team of researchers. The demonstration worked at short range; they did not attempt to develop a long range antenna. The proof of concept exploit helps demonstrate the need for better security and patient alerting measures in remotely accessible medical implants.
Other devices with pacemaker function
Sometimes devices resembling pacemakers, called ICDs (
implantable cardioverter-defibrillatorAn implantable cardioverter-defibrillator is a small battery-powered electrical impulse generator which is implanted in patients who are at risk of sudden cardiac death due to ventricular fibrillation. The device is programmed to detect cardiac arrhythmia and correct it by delivering a jolt of...
s) are implanted. These devices are often used in the treatment of patients at risk from sudden cardiac death. An ICD has the ability to treat many types of heart rhythm disturbances by means of pacing,
cardioversionCardioversion is a medical procedure by which an abnormally fast heart rate or cardiac arrhythmia is converted to a normal rhythm, using electricity or drugs. Synchronized electrical cardioversion uses a therapeutic dose of electric current to the heart, at a specific moment in the cardiac cycle...
, or
defibrillationDefibrillation is the definitive treatment for the life-threatening cardiac arrhythmias, ventricular fibrillation and pulseless ventricular tachycardia. Defibrillation consists of delivering a therapeutic dose of electrical energy to the affected heart with a device called a defibrillator...
.
NASPE / BPEG Defibrillator (NBD) code - 1993
| I |
II |
III |
IV |
| Shock chamber |
Antitachycardia pacing chamber |
Tachycardia detection |
Antibradycardia pacing chamber |
| O = None |
O = None |
E = Electrogram |
O = None |
| A = Atrium |
A = Atrium |
H = Hemodynamic |
A = Atrium |
| V = Ventricle |
V = Ventricle |
|
V = Ventricle |
| D = Dual (A+V) |
D = Dual (A+V) |
|
D = Dual (A+V) |
Short form of the NASPE/BPEG Defibrillator (NBD) code
| ICD-S |
ICD with shock capability only |
| ICD-B |
ICD with bradycardia pacing as well as shock |
| ICD-T |
ICD with tachycardia (and bradycardia) pacing as well as shock |
See also
- Biological pacemaker
The heart is endowed with specialized excitatory and conducting cells that are responsible for the generation and conduction of rhythmic impulses and contractions throughout the heart...
- Cardiology
Cardiology is a specialty dealing with disorders of the heart and blood vessels. The field includes diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology. Physicians specializing in this field of medicine are...
- Electrical conduction system of the heart
The normal electrical conduction in the heart allows the impulse that is generated by the sinoatrial node of the heart to be propagated to the myocardium . The myocardium contracts after stimulation...
- Implantable cardioverter-defibrillator
An implantable cardioverter-defibrillator is a small battery-powered electrical impulse generator which is implanted in patients who are at risk of sudden cardiac death due to ventricular fibrillation. The device is programmed to detect cardiac arrhythmia and correct it by delivering a jolt of...
- Transcutaneous pacing
Transcutaneous pacing is a temporary means of pacing a patient's heart during a medical emergency. It is accomplished by delivering pulses of electric current through the patient's chest, which stimulates the heart to contract....
- Pacemaker syndrome
Pacemaker syndrome is a disease that represents the clinical consequences of suboptimal atrioventricular synchrony or AV dyssynchrony, regardless of the pacing mode, after the pacemaker plantation....
- Infective endocarditis
Infective endocarditis is a form of endocarditis caused by infectious agents. The agents are usually bacterial, but other organisms can also be responsible....
External links