extrasystole

n.
A premature contraction of the heart, resulting in momentary cardiac arrhythmia.

extrasystolic ex'tra·sys·tol'ic (-sĭ-stŏl'ĭk) adj.

(ek′strə-sis′tōlē)
n

A heartbeat occurring before its normal time in the rhythm of the heart and followed by a compensatory pause.

An extra heart beat. See also ectopic heart beat.

(ĕk'strə-sĭs'tə-lē)
n.

An ectopic, usually premature contraction of the heart, resulting in momentary cardiac arrhythmia. Also called premature systole.

A premature cardiac contraction that is independent of the normal rhythm and arises in response to an impulse outside the sinoatrial node.

• atrial e. — premature beat arising from stimuli discharged in atrial wall ectopic to atrial pacemaker and may or may not initiate cardiac irregularity.
• atrioventricular e. — one in which the stimulus is thought to arise in the atrioventricular node.
• interpolated e. — a contraction taking place between two normal heartbeats.
• nodal e. — atrioventricular extrasystole.
• retrograde e. — a premature ventricular contraction followed by a premature atrial contraction, due to transmission of the stimulus backward, usually over the bundle of His.
• triggered e. — cardiac ectopic beats triggered by afterdepolarizations.
• ventricular e. — one in which either a pacemaker or a re-entry site is in the ventricular structure.