extrasystole

noun

1. A premature contraction of the heart, producing an interruption or irregularity in heartbeat rhythm, associated with heart disease or the use of some pharmaceuticals.

   “An extrasystole originating at the rhythmic centre is thus followed by a returning cycle of natural length.”

   “A 30-year-old woman, with no heart disease, was referred to our center with a history of rare episodes of sustained tachycardia and frequent feeling of extrasystoles.”