Extrasystole means an early or extra heartbeat, also called a premature beat or ectopic beat. It arises from a focus outside the heart's normal pacemaker.

Types include:

It may feel like a skipped beat, flutter, thump, or brief pause in the chest. Often the sensation is from the stronger normal beat after the premature one.

Common triggers include stress, poor sleep, caffeine, alcohol, nicotine, fever, dehydration, and some medicines. Isolated extrasystoles are common and are often harmless in people without structural heart disease. Mayo Clinic overview

Seek urgent assessment if palpitations occur with chest pain, fainting or near-fainting, severe breathlessness, sustained rapid heartbeat, or if you have known heart disease. Evaluation may include an ECG, Holter monitor, blood tests, and echocardiography. Treatment is usually directed at triggers or an underlying cause; many people need no specific treatment.