Pacemaker Research Paper

Materials Used In Pacemakers
Image result for what is a pacemakerThe way how a pacemaker is constructed is very crucial to how it would function later. The materials used to construct pacemakers must be non-toxic, sterilisable and able to function in the environmental conditions of the body. Some of the fundamental parts of the pacemaker such as the casing, battery, circuitry and the leads are all made with biocompatible materials or non-toxic materials. Usually, the casing along with the lead is made of titanium or titanium alloy, but the lead is further insulated by a polymer. The circuitry or all the electrical wires are usually made of modified silicon semiconductors and the battery used in a pacemaker is commonly a lithium-ion battery.
Different Types of Pacemaker
Even though pacemaker are made out of the same materials, some still differ from each other.
The North American Society of Pacing and Electrophysiology(NASPE) has classified them by which heart chamber is paced, which chamber is sensed, how the pacemaker responds to a sensed beat, and whether it is programmable. Despite this broad types of models, all pacemakers are essentially composed of a battery that stimulates the heart, lead wires that send electrical pulses towards the heart, and circuitry which is the computer that controls everything in the process. The main four basic types which have different purposes are:

Image result for what is a pacemaker1.Single-Chamber Pacemakers - In a single-chambered pacemaker, only one wire(lead) is placed into a chamber of the heart. Sometimes in the upper chamber called atrium and other times in the lower chamber called ventricle.

Image result for what is a
pacemaker

2.Dual-Chamber Pacemakers - In a dual-chambered pacemaker, wires are placed in two chambers of the heart. One lead is placed in the atrium and the other is placed in the ventricle. This approach is more efficient to matching with the natural pacing of the heart as it can coordinate function between the atria and ventricles.

Image result for rate-responsive pacemakers

3.Rate-Responsive Pacemakers - These have sensors that automatically adjust to changes in a person's physical activity, hence causing them to be able to do sport without worrying about their heart beating at an irregular rhythm.

Image result for biventricular pacemakers

4.Biventricular Pacemakers(used in cardiac resynchronisation therapy) - These use leads attached to three places - the top chamber, and both lower chambers(right and left ventricles). This type of pacemaker is used to synchronise the contractions of the left ventricle with the right ventricle, to improve the ejection fraction in patients with severe and moderately severe symptoms of heart failure.

In addition, there are also two categories in which a pacemaker can be classified as:
Firstly, the temporary pacemakers which are intended for short-term use during hospitalisation when arrhythmia is expected to be temporary and eventually resolve, or because the person requires temporary treatment until a permanent pacemaker can be placed. The pulse generator of a temporary pacemaker is located outside the body, and may be taped to the skin or attached to a belt or to the patient's head. Secondly, the permanent pacemakers are pacemakers intended for long-term use.

The Purpose of the Materials in:
Battery
Image result for pacemaker battery http://www.gettyimages.com/detail/photo/dual-chamber- pacemaker-with-8-year-battery-high-res-stock-photography/128578317
The most common type of battery used in a pacemaker is the lithium-ion battery because of its reliability and lifespan along with having the two components called anode and cathode in which the charge is transferred. Some other batteries such as the nickel-cadmium rechargeable battery and the zinc-mercury battery have also been used in past years but the lithium-ion battery has been proven to be the best. The job of the battery is to store enough energy to stimulate the heart with a jolt of electricity along with providing power to the sensors and timing devices. Therefore, certain batteries are exclusively designed to meet the specific characteristics. First, they have to be able to generate about five volts of power. Second, they must retain the power over many years with a minimum time frame of 4 years, lithium-ion batteries can last 10 years or longer in a cardiac pacemaker. Third, they must have a predictable life cycle, allowing the doctor know when a replacement is required. Finally, they must be able to function when hermetically(airtight) sealed which makes lithium-ion batteries the best choice for a pacemaker.

Leads
Image result for pacemaker leads http://www.epdoc.net/professional/patientpages/Equipment-and-Device-Images.aspx Another part used in a pacemaker are pacemakers leads which are typically composed of titanium alloy. They are thin, insulated wires that are designed to carry electricity between the battery and the heart. The lead is insulated by a polymer such as polyurethane which is a type of synthetic resin and only the metal tip of the lead is exposed as shown in the picture. Depending on the type of pacemaker, it will contain either a single lead for single chamber pacemakers, or two leads for dual chamber pacemakers. With the constant beating of the heart, these wires are chronically flexed and must be resistant to fracture. There are many styles of leads available, with primary design differences such as shaped tip found at the exposed end. Many of the leads have a screw on the tip, which helps anchor them to the inner wall of the heart.

Image result for pacemaker circuitry http://thepansilu.blogspot.com.au/2011/01/ cardiac-pacemakers-engineering-marvels.html
Circuitry
The last but not least crucial part in the design of a pacemaker is the circuitry, or also called the motherboard.
It is the control center of the pacemaker which includes heart monitoring sensors, voltage regulators, timing circuits and externally programmable controls. The circuitry is composed primarily of resistors, capacitors, diodes, semiconductors which when combined using a method known as hybridisation will form a single complex circuit. First, resistors are mostly made of carbon because it is usually available in local markets at a very low cost and they are very durable. Second, capacitors are commonly made of metal foil because it has high reliability, extreme pulse currents, high AC Voltage and much more. Third, diodes are mostly made of silicon because it is the most abundant element on Earth which means it is cheap to acquire along with being a semiconducting material that requires very little effort to convert. Lastly, semiconductors can be made out of silicon and germanium, but silicon is used more commonly than germanium because it is an easy semiconductor to fabricate at low costs, whilst germanium requires a high purity in fabrication. These components are very important to the circuitry as all of them completes each other and will be able to work properly when they are correctly put in place on the
board.