When a heart cannot beat at the correct rate a heart pacemaker can be used. This lifesaving device which was developed in the 1950's is designed to produce a regular electrical stimuli to the heart. In a normal working body the heart's function is to pump away the waste carbon dioxide generated within the body. If the heart is unable to operate in this way unaided, then the pacemaker can be used to artificially perform the motion.
The pacemaker is positioned within a bunch of nerve fibres located in the rear wall of the right atrium, one of the four chambers of the heart. When there, it creates low-intensity electrical impulses (approximately 72 times a minute in a relaxing adult). This induces contractions of the left atria that in turn cause blood to be pumped into the empty ventricles. The impulse generated rapidly passes to a knot of tissue situated close to the junction between the ventricles and the atria. When the impulse reaches this position it is delayed (approximately seven hundredths of a second) which allows precisely the right amount of time for the atria to complete its contractions. Passing through the ventricles is a fan of conducting fibres. These carry the impulse to each of the muscle fibres, causing the ventricles to contract and pump the blood into the arteries.
If the conducting fibres are damaged it can lead to a serious condition called heart block. Heart block is when the heartbeat dramatically slows down and cannot be quickened to cope with the demands of exercise. While a pacemaker cannot actually cure the disease, it can force the heart to beat properly and at least enable the patient to live a normal life.
