D2I2.
cardiovascular

Premature ventricular contractions

A premature contraction (PVC) is a common event where the heartbeat is initiated by Purkinje fibers in the ventricles rather than by the sinoatrial node. PVCs may cause no symptoms or may be perceived as a "skipped beat" or felt as in the chest. PVCs do not usually pose any danger.

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Plain-language summary adapted from Wikipedia. Not medical advice.