Ventricular escape beat reaching the ventricles (normally initiated by the heart's sinoatrial node (SA node), transmitted to the atrioventricular node (AV node), and then further transmitted to the ventricles) falls below the base rate determined by the rate of Phase 4 spontaneous depolarisation of ventricular pacemaker cells. An escape beat usually occurs 2–3 seconds after an electrical impulse has failed to reach the ventricles. This phenomenon can be caused by the sinoatrial node (SA node) failing to initiate a beat, by a failure of the conductivity from the SA node to the atrioventricular node (AV node), or by atrioventricular block (especially third degree
Node graph architecture in which a number of input images have been layered. By connecting many different node types together complex image effects can be produced. The node graph architecture often allows grouping of nodes inside other group nodes. This hides complexity inside of the group nodes, and limits their coupling with other nodes outside the group. This leads to a hierarchy where smaller graphs are embedded in group nodes. In Nuke the group node is simply called the Group node. In the paper Hierarchical Small Worlds in Software Architecture they argue that most large software systems are built in a modular and