Pacemakers, by Denise Buciuman-Coman
An artificial pacemaker is a device that is placed inside the chest to control the rhythm of the heart. It works by sending electrical pulses to various regions of the heart to cause the contractions leading to the heart beat. Usually the sinoatrial node, located in the right atrium of the heart, would act as a natural pacemaker for the heart. However, when this specialized tissue malfunctions or deteriorates in the body, the pacemaker device can be used as a replacement. [3]
Background
The Cardiovascular System
The pacemaker, once placed inside the body, plays a key role in sustaining the cardiovascular system. The cardiovascular system is made up of the heart and it's connected arteries and veins. The cardiovascular system a part of the circulatory system, which is responsible for controlling the flow of blood, nutrients, hormones, oxygen, and other gases throughout the body. [1]
The Heart
A pacemaker is placed inside the chest and is directly connected to the heart. The heart is responsible for facilitating blood flow in the body using contractions.
Blood Flow
The heart can be sectioned into four chambers separated by two sides, the left and the right. The left chambers are the left atrium and left ventricle. The right chambers are the right atrium and right ventricle. Separating these four chambers are four valves, the tricuspid, pulmonary, mitral, and aortic valves. The blood flow is from right to left and alternates between atrium and the ventricle. The oxygenation of blood beings by the entering of deoxygenated blood into the right atrium, then passing the tricuspid valve into the right ventricle, followed by passing through the pulmonary valve to the pulmonary artery where the blood enters the lungs. The lungs oxygenate the blood and it then enters the left atrium, next into the mitral valve, and then to the left ventricle. Finally, the blood reaches the aortic valve into the aorta where it then begins its journey through the rest of the body. [3]
Anatomy
The heart wall is made up of endocardium (inner), myocardium, epicardium (outer), and pericardium layers. The inner endocardium layer is composed of endothelial cells and the myocardium, or middle layer, is made up of cardiac muscle. Myocardium is an aerobic muscle (it uses oxygen to function) where it's composition is 99% contractile cells, 1% autorhythmicity cells.
How It Works
These contractile cells are stimulated by the sinoatrial node (SA), which has an average natural rate of 80-100 A.P. per minute, and surrounding autorhythmic cells. [2] The first electrical signal that the SA sends causes the depolarilization of the cardiac myocytes, which in turn causes the contraction of the heart chambers. After the initial electrical impulse, the signal flows through both the atria which also causes them to contact. It then reaches the atrioventricular node (AV), where the signal is then sent again and spread through the ventricles creating the second contraction. [3]
History
1791 – Galvani discovered that an eel could electrically stimulate frog legs, starting the research on how electricity effects dead organisms. [4,5]
1802 - First successful experiments to electrically stimulate the heart of animals by Aldini in Paris [6]
1862 – Walshe suggests that heart could be electrically stimulated [4]
1889- McWilliam discovered the electrical impulses of the heart using an EKG type device [5]
1927 – Hyman designs an apparatus that could be used to maintain heart function called the "artifical pacemaker" but was very large and originally had a hand crank [4,7]
1932- Hyman improves the artificial hand crank making it battery powered [8]
1951 – Callahan and Bigelow conducted experiments stimulating sinoatrial nodes in dogs to restore natural rhythmic heart beat during hypothermia [9]
1954 – Hopps performed experiments on animals to test snaking wires through veins [10]
1958 – First successful external implanted pacemaker, Furman found that placing electrodes internally that less energy could be used, Arne Larrson received the first internal pacemaker [4,9,10]
1975- Lifespan increased using lithium batteries. [8]
2001 - First wireless pacemaker was produced by BIOTRONIK [11]
Types of Pacemakers
What Pacemakers Treat
Methods of Pacing
Implanting Procedure
Side Effects and Limitations
Battery Technology
Physical Complications
Life With A Pacemaker
Resources
[1] http://www.livescience.com/27585-human-body-system-circulation-infographic.html
[3] Ratner, B.D.; Hoffman, A.S.; Schoen, F.J.; Lemons, J.E. Biomaterials Science: An Introduction to Materials in Medicine, 2nd ed.; Elsevier Academic Press: San Diego, 2004; pp. 472-475;483-485.
[4] ALTMAN, L. K. Arne H. W. Larsson, 86; Had First Internal Pacemaker. The New York Times 2002.
[5] Furman, S. In Principles and techniques of cardiac pacing Haper & Row, Publishers, Inc.: New York, 1970;.
[6] "Surgery: What to Expect - Implanting a Pacemaker." Surgery to Implant a Pacemaker Is Quick, and Typically Done under Local Anesthesia. Medtronic.com, 2010. Web. 20 Feb. 2013. <http://www.medtronic.com/patients/bradycardia/getting-a-device/surgery/index.htm>.
[7] Thalen, H. J. T. In The Artificial cardiac pacemaker. Its history, development and clinical application. Van Gorcum; Charles C. Thomas: Assen; [Springfield, Ill., 1969; . [8] "History of Pacemakers." History of Pacemakers. Biotele, n.d. Web. 19 Feb. 2014.
[9] Furman, S. In Principles and techniques of cardiac pacing Haper & Row, Publishers, Inc.: New York, 1970;.
[10] Siddons, H. In Cardiac pacemakers; Charles C Thomas Publisher: Springfield, Illinois, 1967;.
[11] "New Generation of Pacemakers." New Generation of Pacemakers. Pacemakerclub.com, 27 Aug. 2009. Web. 20 Feb. 2013. <http://www.pacemakerclub.com/public/jpage/1/p/story/a/storypage/sid/13244/content.do>.
