Parasystole is a medical condition that refers to an irregular heartbeat where an accessory pacemaker in the heart activates spontaneously and disrupts the normal rhythm. Some synonyms for this term include extrasystole, ectopic beat, premature ventricular contraction, and ventricular ectopic heartbeat. These conditions are often harmless, but in some cases, they can increase the risk of serious cardiac complications. Other related words that may be used to describe this condition include arrhythmia, tachycardia, fibrillation, and cardiac arrest. It is important to consult with a healthcare provider if you experience any symptoms of arrhythmia, such as heart palpitations or chest pain.