Ectopic pacemakers
Regions of the heart other than the SA node may initiate beats in special circumstances. Such sites are called "ectopic foci or ectopic pacemakers". Ectopic foci may become pacemakers when (1) their own rhythmicity becomes enhanced, (2) the rhythmicity of the higher order pacemakers becomes depressed, or (3) all conduction pathways between the ectopic focus and regions with greater rhythmicity become blocked. Ectopic pacemakers may act as a safety mechanism when normal pacemaking centers fail.
Sayfa 317 - e-kitap
