I had the most amazing experience back in 2020. I saw inside my own heart! I had experienced some irregular heartbeats, so I went for a procedure to identify the problem.
The surgeon put three catheter wires inside my heart to measure how the electrics of the heart operated. He located a minor short-circuit, and worked out that it could not cause me any real problem and was best left alone. He also “took my heart for a spin” to try to reproduce the symptoms I had, but without success.
I was awake during the procedure, watching large monitor displays, and the surgeon explained it to me. When the heart beats, an electrical signal first causes the right atrium chamber to beat. The signal then reaches the AV node, where it is delayed a short time before it travels on to cause the ventricles to beat. The timing delay is just right to ensure efficient pumping of blood. The AV node does other critical things also.