Advances in cardiac pacing have greatly reduced the size of pacemakers
, while improving their longevity and reliability, expanding their cli
nical applications and increasing their sophistication in terms of pro
gramming and automatic features. Significant reductions in the size of
pacing systems have been mainly due to improvements in power sources,
increased circuit integration, hybrid packaging, and the development
of smaller leads and lead connectors. The use of sophisticated micropr
ocessors has transformed some pacemakers into implantable computers. T
he incorporation of memory is enabling modern pacing devices to become
more like Holter monitors, able to store significant amounts of intra
cardiac data. A trend toward the use of sensor technology has been ena
bled pacemakers to provide rate response, taking the place of a damage
d sinus node.