cardiac arrhythmia (EFO_0004269, an Experimental Factor Ontology id) is any disturbances of the normal rhythmic beating of the heart or MYOCARDIAL CONTRACTION. Cardiac arrhythmias can be classified by the abnormalities in HEART RATE, disorders of electrical impulse generation, or impulse conduction. Also known as: arrhythmia, arrhythmias, cardiac, arrythmia, cardiac arrhythmias.