Bigeminy (Latin: Bi-Two Gemini-twins) is a descriptor for a heart arrhythmia in which abnormal heart beats occur every other concurrent beat. A typical example is with bigeminal premature ventricular beats, also known as a premature ventricular contractions/complexes (PVC). Following the PVC there is a pause and then the normal beat returns - only to be followed by another PVC. The continuation of this pairing of beats is an example of bigeminy.
These descriptors can increase depending on the number of beats involved in the abnormal system. If every other beat is abnormal, you can describe it as bigeminal. If every third beat is aberrant, it is trigeminal; every fourth would be quadrigeminal. Typically, if every fifth or more beat is abnormal, the aberrant beat would be termed occasional.
Bigeminy is contrasted with Couplets which are paired abnormal beats. If these concurrent beats number three, they are called triplets and are considered as a brief run of non-sustained Ventricular tachycardia or NS-VT.