An irregular heartbeat or deviation from normal heart rhythm; a condition where the heart beats too fast, too slow, or irregularly.
From Greek a- 'without' + rhythmos 'rhythm.' Medical term coined in the 1800s to describe hearts that don't beat in regular patterns.
Your heart's rhythm is so important that doctors have an entire specialty just studying arythmias—some are harmless (like occasional skips) but others can be deadly if not treated, which is why EKG machines were invented.
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