What is a by gemini heart beat?

Bigeminy: Bigeminy (b)reflects a slightly abnormal heart rhythm that is usually of no serious concern in the absence of other cardiovascular disease. B describes a state where your heart alternates one "normal" beat with one "premature" beat. All people can, at one time or another, experience occasional premature heartbeats. In isolation, these are not usually reason for concern. See a doctor if worried.

Bigeminy: Bigeminy is when the heart rhythm repeats in groups of two beats. This may be normal beat +atrial premature or normal beat plus ventricular premature(or other two beat combo's); it can be seen in normal folks and in people with cardiac abnormalities; discuss with your dr.

-geminal?: You're probably referring to a bi- or trigeminal heart beat. Typically, it refers to premature heat contractions that occur every two (bi) or three (tri) heart beats.