Overview of Pacemakers:
A pacemaker is a device implanted in the chest or abdomen to regulate abnormal heart rhythms. A pacemaker uses low-energy impulses to correct faulty electrical signaling in the heart which causes these abnormal rhythms.
("What is a Pacemaker?", 2012) |
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Pathophysiology:
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Who needs a pacemaker?
Doctors may recommend a pacemaker for individuals who have the following conditions. All of these conditions affect the electrical signaling and rhythm of the heart.
("Who Needs a Pacemaker?", 2012) |
detection:
One of the ways to detect for any of the above diseases is by taking an electrocardiogram (ECG) of the patient. A normal ECG signal as shown on the right (Figure 1) consists of some important characteristics such as:
1) P wave: signifies depolarization in the sinus node and atrial contraction 2) QRS complex: signifies depolarization of the ventricles 3) ST segment: represents the period of time in which the ventricles are isoelectric. 4) T wave: represents the repolarization of the ventricles The primary disease that pacemakers treat is arrhythmias. In Figure 2, we can see the differences between the two ECGs. In the abnormal ECG, the QRS complex is delayed and hence, implies that the patient experiences arrhythmia. ("ECG Basics: Parts of the ECG", 2014) |
Biomaterials:
Materials used in the pacemaker must be bio-compatible, inert, non-toxic, sterilizable, and be able to function in the body's environment.
The outer casing of the pacemaker is made of a titanium alloy. The leads that conduct the impulses are made of a metal alloy as well but are insulated in a polymer such as polyurethane. Only the metal tip of the leads is exposed. All the circuitry and power source is contained in the metal casing.
The circuitry is made of modified silicon semiconductors.
The power source consists of a lithium ion/iodine battery. This type of lithium ion/iodine battery can last for up to 7 years.
("How Pacemakers are Made", 2014)
The outer casing of the pacemaker is made of a titanium alloy. The leads that conduct the impulses are made of a metal alloy as well but are insulated in a polymer such as polyurethane. Only the metal tip of the leads is exposed. All the circuitry and power source is contained in the metal casing.
The circuitry is made of modified silicon semiconductors.
The power source consists of a lithium ion/iodine battery. This type of lithium ion/iodine battery can last for up to 7 years.
("How Pacemakers are Made", 2014)
How does it work?
The power source of the pacemaker charges the pulse generator.
The pulse generator sends impulses to the heart in order to regulate the heartbeat. The electrodes detect the heart's activity, send this information to the pulse generator, and send the responsive impulses to the heart. Depending on the type of pacemaker, these electrodes travel to 1) the right ventricle, in the case of a single chamber pacemaker 2) the right atrium and the right ventricle, in the case of a dual chamber pacemaker. This type of pacemaker coordinates the contractions between the two chambers or 3) an atrium and both ventricles, case of a cardiac resynchronization therapy (CRT) device. This type of pacemaker controls the electrical signaling between the two ventricles. ("How Does a Pacemaker Work?", 2012) |
Pacemakers v. Defibrillators:
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Both pacemakers and defibrillators are used to treat arrhythmias, but the main difference is that pacemakers are generally used to treat slow heartbeats while defibrillators are used to treat fast heartbeats which may lead to cardiac arrest ("Pacemakers & Defibrillators", 2012). While pacemakers use electric pulses to stimulate the heart to beat at a normal rate, defibrillators do the same function as pacemakers as well as shock the heart to resuscitate the patient when their heart beat gets dangerously fast and irregular ("Pacemakers and Implantable Defibrillators", 2014).
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References:
Brock, A. (Director) (2014, November 18). Cardiovascular Physiology: Heart, Part II. Engineering Physiology I. Lecture conducted from ECJ, Austin.
Company-Bosch, E., & Hartmann, E. (2003). ECG Front-End Design is Simplified with MicroConverter. Analog Dialogue, 37(11), 1-5. Retrieved December 1, 2014, from http://www.analog.com/library/analogdialogue/archives/37-11/ecg.html
ECG Basics: Parts of the ECG. (2014, January 1). Retrieved December 1, 2014, from http://www.emergsource.com/?page_id=90
Haddad, S., & Serdijn, W. (2009). The Evolution of Pacemakers: An Electronics Perspective. In Ultra low-power biomedical signal
processing an analog wavelet filter approach for pacemakers (pp. 13-31). Dordrecht: Springer.
How Does a Pacemaker Work? (2012, February 8). Retrieved December 2, 2014, from http://www.nhlbi.nih.gov/health/health-
topics/topics/pace/howdoes
How Pacemakers Are Made. (2014, January 1). Retrieved December 2, 2014, from http://www.madehow.com/Volume-
3/Pacemaker.html
Pacemakers & Defibrillators. (2012, January 1). Retrieved November 29, 2014, from
http://www.cardiacspecialists.com/pacemaker_defibrillators.htm
Pacemakers and Implantable Defibrillators. (2014, August 6). Retrieved November 29, 2014, from
http://www.nlm.nih.gov/medlineplus/pacemakersandimplantabledefibrillators.html
What Is a Pacemaker? (2012, February 8). Retrieved December 2, 2014, from http://www.nhlbi.nih.gov/health/health-
topics/topics/pace
Who Needs a Pacemaker? (2012, February 28). Retrieved December 1, 2014, from http://www.nhlbi.nih.gov/health/health-topics/topics/pace/whoneeds
Company-Bosch, E., & Hartmann, E. (2003). ECG Front-End Design is Simplified with MicroConverter. Analog Dialogue, 37(11), 1-5. Retrieved December 1, 2014, from http://www.analog.com/library/analogdialogue/archives/37-11/ecg.html
ECG Basics: Parts of the ECG. (2014, January 1). Retrieved December 1, 2014, from http://www.emergsource.com/?page_id=90
Haddad, S., & Serdijn, W. (2009). The Evolution of Pacemakers: An Electronics Perspective. In Ultra low-power biomedical signal
processing an analog wavelet filter approach for pacemakers (pp. 13-31). Dordrecht: Springer.
How Does a Pacemaker Work? (2012, February 8). Retrieved December 2, 2014, from http://www.nhlbi.nih.gov/health/health-
topics/topics/pace/howdoes
How Pacemakers Are Made. (2014, January 1). Retrieved December 2, 2014, from http://www.madehow.com/Volume-
3/Pacemaker.html
Pacemakers & Defibrillators. (2012, January 1). Retrieved November 29, 2014, from
http://www.cardiacspecialists.com/pacemaker_defibrillators.htm
Pacemakers and Implantable Defibrillators. (2014, August 6). Retrieved November 29, 2014, from
http://www.nlm.nih.gov/medlineplus/pacemakersandimplantabledefibrillators.html
What Is a Pacemaker? (2012, February 8). Retrieved December 2, 2014, from http://www.nhlbi.nih.gov/health/health-
topics/topics/pace
Who Needs a Pacemaker? (2012, February 28). Retrieved December 1, 2014, from http://www.nhlbi.nih.gov/health/health-topics/topics/pace/whoneeds