antidromic

Imagine a highway where all traffic is required to flow south. If a vehicle suddenly enters and drives north, it is moving against the established current. This is the essence of "antidromic." It is a specialized scientific term used mostly in electrophysiology (especially neurophysiology and cardiology). It describes an electrical impulse—like a signal in your nerves or heart—that travels in the opposite direction of its normal, physiological path. While "orthodromic" describes the usual direction, "antidromic" is the biological equivalent of going the wrong way down a one-way street.

The word "antidromic" is derived from the Greek words anti (against) and dromos (course or running). Therefore, it literally means "running against the course." While the etymology sounds general, English speakers do not use this word for everyday reversals; you wouldn't say a car is driving "antidromic." Instead, this term lives mostly in technical writing by scientists and clinicians.

In *neurology*, this is its most common home. An antidromic impulse refers to a nerve signal traveling backward along an axon—opposite to the usual physiological direction, which is typically from the cell body toward the nerve terminals. Researchers can artificially stimulate nerves to send signals “backward” toward the cell body to map connections and study how pathways are organized. It is a useful concept in electrophysiology and nerve conduction studies.

In *cardiology, the term appears in discussions of certain re-entrant heart rhythms, especially in Wolff–Parkinson–White (WPW) syndrome. In antidromic AV re-entrant tachycardia, the impulse travels from the atria to the ventricles through an accessory pathway and returns through the AV node—the reverse of the more common orthodromic* pattern—often producing a rapid (and typically wide-complex) rhythm.

So, while you likely won't hear this word at a dinner party, it is a precise technical tool used to describe the phenomenon of biological signals reversing their standard journey.