Cardiac pacemakers are devices used to treat arrhythmia. They are placed in the chest or abdomen to help regulate abnormal heart rhythms. It uses electrical impulses to for normal heart rate. It sends signals when it senses your heart is beating irregularly or two slow. Pacemakers consist of two parts. One part, called the pulse generator contains the battery and the electronics that regulate heartbeat.
Cardiac devices are of two types- CRT (Cardiac Re synchronize Therapy) devices and LVADs (Left Ventricle Assist Devices). These devices are run by battery. Lead tubes are used to connect the device and heart that carry the signals to the heart. These batteries usually have life for 3-6 years. The pulse generator are made of titanium, a metal that is 10 times as strong as steel but lighter. Titanium and two of its alloys, niobium and tantalum are bio compatible. The batteries of the pacemakers are designed such that they have reliability for long period.
Earlier, nickel-cadmium , zinc-mercury and nuclear batteries were used. The nickel-cadmium batteries were used in the beginning of pacemaker implants in 1952. The disadvantages of these batteries were short life and problem of recharging. Then zinc-mercury batteries were used in 1960 s and it had a disadvantage of fluid leakage. Nuclear batteries were also used for some period which used plutonium. However the presence of plutonium in blood is highly toxic and fatal.
Modern pacemakers use lithium-iodide batteries. These batteries have a lot of advantages over the earlier ones. Lithium-iodide batteries have longevity, compact sizes, corrosion resistance, minimum weight and have no gas generation. Hence lithium iodide batteries will be in use until the invention of a new technology.