Correlation between two focal origin and the division of quadrants.

<p>Correlation between atrial focal origin (A) and the body surface polarity (B), corresponding to ectopic pacing at the inferior vena cava (Ai) right atrial appendage (Aii). In B, both the front (left panels) and back (right panels) of the torso are shown. The quadrants on the torso and the atria are illustrated in B (i),(ii) and C. Qt_i indexes the quadrants of the torso B(i) and (ii), and the Qa_i indexes quadrants of the atria C(i) and (ii).