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Figure 3 LA area and simultaneous LA pressure and ECG (A). The LA pressure–area relation is composed of two loops: the A loop, expressing the LA pump function, and the V loop, expressing the LA reservoir function (B). During the filling period, the curve is directed upward and to the right, and after maximal pressure and area of the filling period have been reached, the curve turns clockwise and downward, corresponding to the passive emptying and, subsequently, active emptying phases. LA pressures and areas during the ascending limb of the V loop and the calculated monoexponential curve are also shown.