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Figure 5 Activation patterns in a patient with atypical AF. Reentry involving the lower RA traveled around the inferior vena cava in a clockwise direction. The cycle length was 186 ms. Splines H and A are located in the lateral region; splines B and C in the posterior region; splines D, E and F in septal region; and spline G in anteroseptal region of the RA. Electrode pairs 7–8 were located in the lower RA. Left panel, Reentrant impulse is divided into two wave fronts: the first one shortcuts in the posterolateral wall (B_4–5) and reenters the isthmus region, and the second goes up the lateral wall and down the septal wall. Right panel, By the time the second wave front reaches the low septal region, the first wave front passes through the isthmus and reactivates the lateral wall.