- An abnormal heart rhythm. In an arrhythmia the heartbeats may be too slow, too rapid, too 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 and ventricular fibrillation). When a single heartbeat occurs earlier than normal, it is called a premature contraction. The term arrhythmia comes from the Greek a-, loss + rhythmos, rhythm = loss of rhythm.
* * *Loss or abnormality of rhythm; denoting especially an irregularity of the heartbeat.rhythm. Cf.:dysrhythmia. [G. a- priv. + rhythmos, rhythm]- juvenile a. SYN: sinus a..- nonphasic sinus a. sinus a. in which variations in rhythm are not related to the phases of respiration.- phasic sinus a. sinus a. in which the irregularity is related to the phases of respiration, the rate being faster in inspiration and slower in expiration.- respiratory a. phasic sinus a. or any other rhythm fluctuation induced by respiratory fluctuation.- sinus a. rhythmic, repetitive irregularity of the heartbeat, the heart being under the control of its normal pacemaker, the sinoatrial node. SYN: juvenile a..
* * *ar·rhyth·mia ā-'rith-mē-ə n an alteration in rhythm of the heartbeat either in time or force
* * *n.any deviation from the normal rhythm (sinus rhythm) of the heart. The natural pacemaker of the heart (the sinoatrial node), which lies in the wall of the right atrium, controls the rate and rhythm of the whole heart under the influence of the autonomic nervous system. It generates electrical impulses that spread to the atria and ventricles, via specialized conducting tissues, and cause them to contract normally. Arrhythmias result from a disturbance of the generation or the conduction of these impulses and may be intermittent or continuous. They include ectopic beat (extrasystoles), ectopic tachycardias (see supraventricular tachycardia, ventricular tachycardia), fibrillation, and heart block (which is often associated with slow heart rates). Symptoms include palpitations, breathlessness, and chest pain. In more serious arrhythmias the Stokes-Adams syndrome or cardiac arrest may occur. Arrhythmias may result from most heart diseases but they also occur without apparent cause.
* * *ar·rhyth·mia (ə-rithґme-ə) [a-1 + rhythm + -ia] 1. a disturbance in or loss of regular rhythm. 2. especially, any variation from the normal rhythm of the heartbeat; it may be an abnormality of either the rate, regularity, or site of impulse origin or the sequence of activation. The term encompasses abnormal regular and irregular rhythms as well as loss of rhythm. Cf. dysrhythmia and see also entries under rhythm.
Medical dictionary. 2011.