Figure 1.

In echocardiographic four-chamber view, the main structures of the crux of the heart are depicted. The AVV, the LPA, and the RPA form the main triangle, which in turn is formed by two right-angled triangles. The left right-angled triangle is composed by three elements: The LC of the AVV valve, the VSD, and LPA. Simple geometric rules apply to these triangles, and therefore, relations between the different elements can be established. AVV: Atrioventricular valve, LC: Left component, LPA: Left primary annulus, RPA: Right primary annulus, SA: Secondary annulus, VSD: Ventricular septal defect, mAVVI: Modified atrioventricular valve index, LVII: Left ventricular inflow index, inVSD: Indexed ventricular septal defect, inSA: Indexed secondary annulus