An interactive, Flash animated diagram of the human heart, focusing on the paths of electrical currents that control the heartbeat, and how an Electrocardiogram (ECG) would read them. By placing electrodes on the surface of the skin, the electrical activity can be read: starting from the sinoatrial (SA) node, where the first impulse is generated, and so on. Click through an animated slideshow to see how the electrical currents travel, and how they’re interpreted by an ECG.