Sinoatrial block a lag between the time that the SA node fires and actual depolarization of the atria. This rhythm is not recognizable on an ECG strip because a strip does not denote when the SA node fires. It can be detected only during an electrophysiology study when a small wire is placed against the SA node from within the heart and the electrical impulses can be recorded as they leave the p-cells in the centre of the node [ see pacemaker potential ], followed by observing a delay in the onset of the p wave on the ECG. Second degree SA
Node (physics) Node (physics) A node is a point along a standing wave where the wave has minimum amplitude. For instance, in a vibrating guitar string, the ends of the string are nodes. By changing the position of the end node through frets, the guitarist changes the effective length of the vibrating string and thereby the note played. The opposite of a node is an anti-node, a point where the amplitude of the standing wave is a maximum. These occur midway between the nodes. Standing waves result when two sinusoidal wave trains of the same frequency are moving in opposite directions in