Palpitations were rapid and irregular beatings of the heart.

In 2268, Dr. Leonard McCoy asked Lieutenant Commander Montgomery Scott if he was experiencing palpitations after exposure to a gas grenade. (TOS: "Spectre of the Gun")

In 2370, during her examination of "Jayden" (Data), Talur asked him if he had experienced palpitations. (TNG: "Thine Own Self")

Soon after, Reginald Barclay believed that the palpitations he was experiencing were a symptom of the Terellian Death Syndrome or possibly Symbalene blood burn. Thankfully, Dr. Beverly Crusher assured him he only had Urodelan flu. (TNG: "Genesis")

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