| pacemaker | 1. <apparatus, physiology> An object or substance that influences the rate at which a certain phenomenon occurs, often used alone to indicate the natural cardiac pacemaker or an artificial cardiac pacemaker. 2. <biochemistry> A substance whose rate of reaction sets the pace for a series of interrelated reactions. (24 Mar 1998) |
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| pacemaker, artificial | A device designed to stimulate, by electric impulses, contraction of the heart muscles. It may be temporary (external) or permanent (internal or internal-external). (12 Dec 1998) |
| pacemaker failure | Failure of an artificial pacemaker to generate or deliver effective stimuli to the myocardium. (05 Mar 2000) |
| pacemaker output | Electrical energy delivered into a standard load (500 ohms resistance). (05 Mar 2000) |
| pacemaker potential | The voltage inscribed by impulses from an artificial electronic pacemaker. (05 Mar 2000) |
| pacemaker sensitivity | The minimum cardiac activity required to consistently trigger a pulse generator. (05 Mar 2000) |
| pacemaker syndrome | <syndrome> The occurrence of symptoms relating to the loss of atrial-ventricular synchrony in ventricularly paced patients, or symptoms caused by inadequate timing of atrial and ventricular contractions in paced patients. (05 Mar 2000) |
| refractory period of electronic pacemaker | The time required to restore full sensitivity after detecting cardiac activity or delivering a pacing impulse. (05 Mar 2000) |
| pervenous pacemaker | An artificial pacemaker passed through the venous circulation into the right side of the heart. (05 Mar 2000) |
| runaway pacemaker | Rapid heart rates over 140/min caused by electronic circuit instability in an implanted pulse generator. (05 Mar 2000) |
| wandering pacemaker | A disturbance of the normal cardiac rhythm in which the site of the controlling pacemaker shifts from beat to beat, usually between the sinus and A-V nodes, often with gradual sequential changes in P waves between upright and inverted in a given ECG lead. Synonym: shifting pacemaker. (05 Mar 2000) |
| shifting pacemaker | A disturbance of the normal cardiac rhythm in which the site of the controlling pacemaker shifts from beat to beat, usually between the sinus and A-V nodes, often with gradual sequential changes in P waves between upright and inverted in a given ECG lead. Synonym: shifting pacemaker. (05 Mar 2000) |
| subsidiary atrial pacemaker | Secondary source for rhythmic control of the heart, available for controlling cardiac activity if the sinoatrial pacemaker fails; located within the crista terminalis and atrial free wall near the inferior vena cava. (05 Mar 2000) |
| nuclear pacemaker | A nuclear-powered unit used to generate the electrical current for artificially pacing the heart; replaced by units using long-life nickel-cadmium and other power sources. (05 Mar 2000) |
| demand pacemaker | A form of artificial pacemaker usually implanted into cardiac tissue because its output of electrical stimuli can be inhibited by endogenous cardiac electrical activity. (05 Mar 2000) |