The normal heart-beat is initiated by a signal from the pacemaker cells
in the heart which is very rapidly conducted over the whole heart so that its
billions of muscle cells get the message simultaneously and contract
collectively to provide an effective heart-beat. The conducting pathways
can, however, become diseased. The heart may then beat too quickly
(tachycardia) or too slowly (bradycardia) for comfort. Arrhythmias can often
now be prevented or treated with the appropriate tablets, though this
sometimes requires expert diagnosis of which type of arrhythmia is causing
the trouble, if treatment is to be effective and safe. Complete heart block is
responsible for one type of bradycardia and may be complicated by episodes
of temporary cardiac arrest. This danger can nowadays be avoided by .
implanting a small artificial pacemaker which will allow the patient to get
back to normal life again. The modern pacemaker can be implanted quite
easily under local anaesthetic. It consists of a small box of micro-electronic
circuitry powered by a small but very long-life battery (5-10 years),
attached to a wire whose tip is lodged within the heart. It works by giving
an artificial signal to initiate contraction each time that the heart fails to
generate its own signal.