Bradycardia

Bradycardia is a slower-than-normal heart rate, typically fewer than 60 beats per minute in adults at rest. It may be harmless or reflect a problem with the heart’s electrical system.

Cardiac conduction system: The network of specialized heart cells that generates and conducts electrical impulses coordinating heartbeats. Its signal pathway sets the heart rate and can slow at several points.
Electrocardiogram: A tracing of the heart’s electrical activity over time, commonly called an ECG or EKG. It helps identify the rhythm and conduction pattern underlying a slow pulse.
Athlete's heart: A set of structural and functional cardiac adaptations associated with sustained athletic training. Training-related resting bradycardia can occur without disease or symptoms.
Tachycardia: A heart rate faster than normal, commonly defined in adults at rest as over 100 beats per minute. It is the rate-direction opposite of bradycardia.
Sinoatrial node: A cluster of cells in the right atrium that normally initiates each heartbeat. An abnormally slow firing rate here can produce sinus bradycardia.
Holter monitor: A portable electrocardiography device that records heart rhythm continuously, usually for a day or longer. It can detect intermittent bradycardia missed during a brief clinic ECG.
Vasovagal syncope: A fainting episode caused by a reflex that lowers blood pressure and may slow heart rate. The reflex can produce transient bradycardia alongside fainting.
Arrhythmia: A disturbance in the rate, regularity, or electrical conduction of the heartbeat. Bradycardia describes a slow rate, while arrhythmia covers a broader range of rhythm disorders.
Atrioventricular block: A delay or interruption in electrical conduction from the atria to the ventricles. Blocked or delayed impulses can leave the ventricles beating too slowly.
Pacemaker: A device that uses electrical pulses to maintain an adequate heart rate when the heart’s own rhythm is insufficient. It treats selected symptomatic bradycardias caused by persistent electrical-system disease.

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