Premature atrial contraction Premature atrial contraction Premature atrial contractions (PACs), also known as atrial premature complexes (APC) or atrial premature beats (APB), are a common cardiac dysrhythmia characterized by premature heartbeats originating in the atria. While the sinoatrial node typically regulates the heartbeat during normal sinus rhythm, PACs occur when another region of the atria depolarizes before the sinoatrial node and thus triggers a premature heartbeat. The exact cause of PACs is unclear; while several predisposing conditions exist, PACs commonly occur in healthy young and elderly people. Elderly people that get PACs usually don't need any further attention besides follow ups due to
Node (circuits) Dots used to mark nodes on a circuit diagram are sometimes referred to as "meatballs". Node (circuits) In electrical engineering, a node is any point on a circuit where the terminals of two or more circuit elements meet. In circuit diagrams, connections are ideal wires with zero resistance, so a node may consist of the entire section of wire between elements, not just a single point. According to Ohm's law, "V = IR", the voltage across any two points of a node with negligible resistance is showing that the voltage at every point of a node is the same. However,