| 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) |
|---|---|
| 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) |
| 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) |
| artificial pacemaker | Any device that substitutes for the normal pacemaker and controls the rhythm of the organ; especially an electronic cardiac pacemaker, which may be implanted in the chest, with electrodes attached to the external cardiac surface, or passed through the venous circulation into the right side of the heart (pervenous pacemaker). (05 Mar 2000) |
|---|---|
| cardiac pacemaker | An electrical device which delivers a small stimulant shock to the heart to effect cardiac contraction at a pre-determined rate. Many of today's pacemakers have two main components: the electrodes and the transducer (pulse generator). The electrodes are wires which are placed into the circulatory system and make physical contact with the heart muscle. A small electrical discharge from the pacemaker electrode stimulates the muscular wall of the heart to contract, thus pumping blood in an organised fashion. The transducer is a small device, usually implanted under the skin, that generates the electrical discharge at a pre-determined frequency. Transducers can monitor your heart's rate of contraction and deliver an electrical shock only when the heart is going too slow. (27 Sep 1997) |
| 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) |
| diaphragmatic pacemaker | A device that paces the diaphragm, used in patients with chronic ventilatory insufficiency resulting from malfunction of the respiratory control centre on certain types of phrenic nerve malfunction. (05 Mar 2000) |
| ectopic pacemaker | Any pacemaker other than the sinus node. (05 Mar 2000) |
| electric cardiac pacemaker | An electric device that can substitute for the normal cardiac pacemaker, controlling the heart's rhythm by artificial electric discharges. Synonym: electronic pacemaker. (05 Mar 2000) |
| electronic pacemaker | An electric device that can substitute for the normal cardiac pacemaker, controlling the heart's rhythm by artificial electric discharges. Synonym: electronic pacemaker. (05 Mar 2000) |
| electronic pacemaker load | The impedance to the output, the standard load being 500 ohms resistance ± 1%. (05 Mar 2000) |