pacemaker /pace·mak·er/ (pās´māk″er)
Pacemaker
pacemaker
pacemaker,
pacemaker,
pacemaker
1. that which sets the pace at which a phenomenon occurs.
2. the natural cardiac pacemaker or an artificial cardiac pacemaker.
3. in biochemistry, a substance whose rate of reaction sets the pace for a series of related reactions.
artificial cardiac pacemaker a device designed to reproduce or regulate the rhythm of the heart. It is worn by or implanted in the body of the patient, is battery-driven, is usually triggered or inhibited to modify output by sensing the intracardiac potential in one or more cardiac chambers, and may also have antitachycardia functions. Many are designated by a three to five letter code used to categorize them functionally.
cardiac pacemaker a group of cells rhythmically initiating the heartbeat, characterized physiologically by a slow loss of membrane potential during diastole; usually it is the sinoatrial node.
demand pacemaker an implanted cardiac pacemaker in which the generator stimulus is inhibited by a signal derived from the heart's electrical activation (depolarization), thus minimizing the risk of pacemaker-induced fibrillation.
dual chamber pacemaker an artificial pacemaker with two leads, one in the atrium and one in the ventricle, so that electromechanical synchrony can be approximated.
ectopic pacemaker any biological cardiac pacemaker other than the sinoatrial node; it is normally inactive.
escape pacemaker an ectopic pacemaker that assumes control of cardiac impulse propagation because of failure of the sinoatrial node to initiate one or more impulses.
fixed-rate pacemaker an artificial cardiac pacemaker set to pace at only a single rate.
rate responsive pacemaker an artificial cardiac pacemaker that can deliver stimuli at a rate adjustable to some parameter independent of atrial activity.
runaway pacemaker a malfunctioning artificial cardiac pacemaker that abruptly accelerates its pacing rate, inducing tachycardia.
secondary pacemaker ectopic p.
single chamber pacemaker an implanted cardiac pacemaker with only one lead, placed in either the atrium or the ventricle.
wandering atrial pacemaker a condition in which the site of origin of the impulses controlling the heart rate shifts from one point to another within the atria, almost with every beat.
pace·mak·er (p s m k r)n. 1. A part of the body, such as the specialized mass of cardiac muscle fibers of the sinoatrial node, that sets the pace or rhythm of physiological activity. 2. Any of several usually miniaturized and surgically implanted electronic devices used to stimulate or regulate contractions of the heart muscle. 3. A substance whose rate or reaction sets the pace for a series of chain reactions. 4. The rate-limiting reaction itself. pace making adj. & n. |   fixed-rate artificial pacemaker |
Pacemaker
An electrical device that has electrodes attached to the heart to electrically stimulate the heart to beat normally. Pacemakers can be internal (placed under the skin) or external, with the electrodes placed on the skin or threaded through a tube placed into the heart.
pacemaker
Etymology: L, passus, step; AS, macian, to make
1 also called cardiac pacemaker. the sinoatrial node composed of specialized nervous tissue and located at the junction of the superior vena cava and the right atrium. It initiates the contractions of the atria, which transmit the impulse onto the atrioventricular (AV) node, thereby initiating the contraction of the ventricles. An ectopic or idioventricular pacemaker, originating in the atria, AV node, or ventricle, may cause contractions in cases of abnormal heart functioning.
2 an electric apparatus used in most cases to increase the heart rate in severe bradycardia by electrically stimulating the heart muscle. A pacemaker may be permanent or temporary, emit the stimulus at a constant and fixed rate, or fire only on demand.
pacemaker,
n 1. the sinoatrial node comprises specialized tissue and is positioned at the junction of the right atrium and superior vena cava; primar-ily responsible for initiating the contractions of the atria which transmit the impulse to atrioventricular node resulting in contraction of the ventricles. A pacemaker that does not function properly may cause irregularities in the function of the heart.
2. an electrical device that is temporarily or permanently implanted in the body to improve the heart rate by using electric impulses to stimulate the heart muscles. Also called
cardiac pacemaker.
2. an electrical device that is temporarily or permanently implanted in the body to improve the heart rate by using electric impulses to stimulate the heart muscles. Also called
cardiac pacemaker.
pacemaker,
n an electrical device used to maintain a normal sinus rhythm in heart muscle contraction. Pacemakers can be permanent indwelling appliances. The use of electronic devices on patients with pacemakers is now considered permissible because of modern shields. The device may also have a defibrillator. Also called
cardiac pacemaker.
cardiac pacemaker.
pacemaker
1. an object or substance that controls the rate at which a certain phenomenon occurs; often used alone to indicate an artificial cardiac pacemaker; however, there are other natural and artificial pacemakers.
2. In biochemistry, a pacemaker is a substance whose rate of reaction sets the pace for a series of interrelated reactions.
asynchronous pacemaker
(1) an implanted cardiac pacemaker in which the induced ventricular rhythm is independent of the atrium; it is usually set at a fixed rate of ventricular stimulation.
pacemaker cells
(1) cells within the heart capable of spontaneous discharge.
gastric pacemaker
(1) a saddle-shaped area of the greater curvature of the stomach at the junction of its proximal and middle thirds, which regulates the frequency of gastric contractions.
phrenic pacemaker
(1) a device designed to facilitate respiration by converting radiofrequency signals into electrical impulses that stimulate the phrenic nerve, resulting in contraction and flattening of the diaphragm and improved inspiration of air.
pacemaker therapy
implantation of a pacemaker device in animals usually for the treatment of symptomatic bradyarrhythmias.
pacemaker syndrome
falling arterial pressure, low cardiac output and congestive heart failure, usually due to a suboptimal pacing mode.
uterine pacemaker
either of the two regulating centers that control uterine contractions.
wandering pacemaker
a condition in which the site of origin of the impulses controlling the heart rate shifts from the head of the sinoatrial node to a lower part of the node or to another part of the atrium.
pacemaker
Cardiology An electronic device which generates timed electric pulses that stimulate ventricular contractions. See Artificial pacemaker, Asynchronous pacemaker, Automatic antitachycardia pacemaker, Cardiac pacemaker, Circadian
pacemaker, Demand pacemaker, Dual chamber pacemaker, External pacemaker, Programmable pacemaker, Triggered pacemaker, Wandering pacemaker.
How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content.
| ?Page tools | ||
|---|---|---|
|