Here are definitions of medical terms related to palpitations.
Adrenaline: One of the chemical messengers in the body that causes the heart to beat faster.
Arrhythmia: Any rhythm that is not the normal rhythm of the heart; it may mean a slow or fast heart rate or an irregular rhythm.
Arteries: The blood vessels that carry blood away from the heart and around the body.
Atria: The two upper chambers of the heart (the left atrium and the right atrium), which take in blood from the veins.
Atrial fibrillation: A condition in which the heartbeat is irregular and often rapid
Atrial flutter: A condition in which the upper chambers of the heart contract rapidly but regularly.
AV (atrioventricular) node: A relay station between the atria and ventricles that causes a delay in the electrical impulse to permit the atria to finish contracting (emptying) before ventricular contraction
Bradycardia: A slow heart rate (less than about 60 beats per minute).
Cardiac catheterization: A procedure in which thin tubes are threaded through the blood vessels to the heart to detect blockages indicative of coronary artery disease. This test is also used to see how well the heart muscle contracts and the valves function.
Catecholamines: Chemical messengers in the body that send signals to the sinus node to increase the heart rate; one such catecholamine is adrenaline (epinephrine).
Coronary artery disease: Blockages of the arteries that supply blood to the heart muscle.
Echocardiography: A noninvasive test that uses sound waves to produce images of the heart on a monitor.
Ectopic beats (extrasystoles): The term used to describe a short sequence of extra heartbeats (premature contractions).
Electrocardiogram (ECG or EKG): A recording of the electrical activity of the heart.
Heart block: A condition in which the impulses from the heart's upper chambers are delayed or blocked from reaching the lower chambers.
Normal sinus rhythm: The normal rhythm of the heart.
Pacemaker: An electrical device that delivers electrical impulses to produce a heartbeat of desired frequency. Implantable pacemakers are the mainstay of treatment for bradycardia, and are also useful for sometachycardias.
Palpitations: Awareness of the heart beating; the heartbeat may feel fast, slow, forceful, or irregular.
Sick sinus syndrome: A disorder in the heart's sinus node that affects how heartbeats are generated and how they are conducted. It usually causes a slow heart rate that may cause a person to faint. A related disorder is bradycardia-tachycardia syndrome, which involves alternating bouts of fast and slow rhythms.
Sinus node: The body's natural "pacemaker," which lies in the heart's right atrium and generates a rhythm of electrical impulses to cause the heart muscle to contract.
SVTs (supraventricular tachycardias): Fast heartbeats that originate above the ventricles (in the atria, AV node, or both).
Tachycardia: The term used to describe a rapid heartbeat of greater than 100 beats per minute.
Veins: The blood vessels that carry blood back to the heart.
Ventricles: The two lower chambers of the heart (the left ventricle and the right ventricle), which pump blood out of the heart and into the arteries.
Ventricular tachyarrhythmias: Fast heartbeats that originate in the ventricles.