cardiac pacemaker

pacemaker /pace·mak·er/ (pās´māk″er)

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.

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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.

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cardiac pacemaker.

See pacemaker.

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cardiac dysrhythmia (disrith´mē),

n an irregular or abnormal heartbeat rhythm. Also known as
cardiac arrhythmia.

cardiac massage,

n See massage, cardiac.

cardiac output,

n the volume of blood put out by the heart per minute; the product of the stroke volume and the heart rate per minute.

cardiac pacemaker,

n See pacemaker.

cardiac surgery,

n an operative procedure used to treat a disease of the heart or its blood vessels.

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cardiac pacemaker

A device that delivers a small electric shock to the heart to effect cardiac contraction at a pre-determined rate