What is the difference between lvidd & lvedd?

Internal vs external: Both terms refer to the diameter of the left ventricle at the end of diastole (right as the chamber finishes filling). Lvidd refers to the internal diameter, measuring the diameter of the chamber but not including the thickness of the chamber walls. Conversely, the lvedd refers to the external diameter of the chamber, including the thickness of the interventricular septum and the posterior wall.