Atrial Fibrillation

Atrial fibrillation is a disturbance in the heart's rhythm in which the upper chambers (the atria) quiver rapidly and irregularly rather than contracting in a coordinated way. This irregular activity affects how efficiently blood moves through the heart, and it often leads to a fast, chaotic heartbeat that can be heard through a stethoscope or felt as an irregular pulse. Owners sometimes notice signs such as reduced energy, reluctance to exercise, faster breathing at rest, or episodes of weakness or collapse. In other cases, the irregular rhythm is discovered during a routine examination when no outward signs have been observed. Atrial fibrillation is more common in larger breed dogs, and it can occur alongside other heart conditions or on its own. This page explores the signals that may be present, the mechanisms that lead to the rhythm disturbance, the investigations used to confirm and characterise it, and the range of approaches that exist for managing it over time.