an area in the heart that initiates abnormal beats. Ectopic foci may occur in both healthy and diseased hearts and are usually associated with irritation of a small area of myocardial tissue. They are produced in association with myocardial ischemia, drug (catecholamine) effects, emotional stress, and stimulation by foreign objects, including pacemaker catheters. Also called ectopic pacemaker.
ec·top·ic fo·cus(ek-top'ik fō'kŭs)
An irritable zone of myocardium capable of initiating ectopic beats or assuming the function of a pacemaker.