Electrical activation of the right atrium in atrial flutter

Electroanatomical (3D) mapping using the CARTO system. The right atrium (RA) is depicted in the LAO projection. The circular "cutout" area in the forefront of the picture represents the tricuspid valve annulus. The red area is the inferolateral RA, the yellow-green area at the bottom of the picture is near the inferior vena cava, the yellow dots are at the region of the His bundle (AV node), and the blue area is the superior RA. The top of the picture is the superior vena cava region. The color (red-orange-yellow-green-blue-purple) represents the direction of electrical activation in the RA during typical (counterclockwise) atrial flutter. Each flutter wave seen on ECG represents a single electrical activation of this entire circuit.