Artificial regulation of the beating of the heart
An implantable pacemaker is an artificial device used to electronically pace the heart. Every year almost 30 000 new devices are fitted, and this year the 500 000th device was implanted in the United Kingdom.1 They continue to become more common as heart disease rises in an ageing population. A basic understanding of their indications and purposes is important for any junior doctor.
The heart’s conducting system has the dual properties of self excitation and impulse propagation (fig 1).2 It provides a regular heart rate and ensures that atrial systole occurs before simultaneous contraction of the ventricles. A pacing device can provide a substitute pacing rate or bypass a conduction block.
Each device consists of a box and battery supply.3 Lead wires carry electrical impulses between the pacemaker and heart, which in turn generate action potentials and cardiac contractions. The pacing impulse is seen as a short vertical spike on an electrocardiogram.4