Arrhythmias

n. irregular heartbeat (Medicine)

Cardiac arrhythmia is any of a group of conditions in which the electrical activity of the heart is irregular or is faster or slower than normal. Some arrhythmias are life-threatening medical emergencies that can cause cardiac arrest and sudden death. Others cause aggravating symptoms, such as an awareness of a different heart beat, or palpitation, which can be annoying. Some are quite minor and can be regarded as normal. Sinus arrhythmia is the mild acceleration followed by slowing of the normal rhythm that occurs with breathing. In adults the normal resting heart rate ranges from 60 beats per minute to 100 beats per minute. The normal heart beat is controlled by a small area in the upper chamber of the heart called the sinoatrial node or sinus node. The sinus node contains specialized cells that have spontaneous electrical activity that starts each normal heart beat.
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An arrhythmia is an abnormality in the heart's rhythm, or heartbeat pattern. [more]Arrhythmias - Community and Resources

Noun
1. an abnormal rate of muscle contractions in the heart
(synonym) cardiac arrhythmia
(hypernym) heart disease, heart condition, cardiopathy
(hyponym) flutter

Abnormal heart rhythms. The heartbeats may be too slow, too rapid, irregular, or too early. Rapid arrhythmias (greater than 100 beats per minute) are called tachycardias. Slow arrhythmias (slower than 60 beats per minute) are called bradycardias. Irregular heart rhythms are called fibrillations (as in atrial fibrillation). When a single heartbeat occurs earlier than normal, it is called a premature contraction.

Abnormal heart rhythm due to electrical disturbances in the atria (the upper chambers of the heart) or the AV node "relay station", leading to fast heart beats. Examples of atrial arrhythmias includes atrial fibrillation, atrial flutter, and paroxysmal atrial tachycardia (PAT).

Abnormally rapid heart rhythms, medically termed tachycardia.

Abnormally slow heart rhythms, medically termed bradycardia.

Abnormal rapid heart rhythms (arrhythmias) that originate in the lower chambers of the heart (the ventricles). Ventricular arrhythmias include ventricular tachycardia and ventricular fibrillation. Both are life threatening arrhythmias most commonly associated with heart attacks or scarring of the heart muscle from previous heart attack.

See Arrhythmias, atrial.