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Figure 1 Display of the torso anatomy with the 62 lead positions (A) and a body surface Fl wave integral map (B). The lead array integrates V₁–V₆ (six open circles in precordial area) and consists of 14 vertically applied straps (marked A to P; no straps at positions B and O; strap A located at right anterior axillary line) each containing up to 8 electrodes at 12 possible locations (marked 1 to 12; electrode 1 situated at top of each strap). The integral map was computed over the initial time period (indicated by gray zone between two markers) of a CCW typical Fl wave episode obtained in patient 16. The scalar waveform below the map is shown at a high gain setting and was recorded at the E9 electrode position (left lower anterior chest). The map layout relates to the torso anatomy (panel A) in that the left and right part of the map correspond to the front and back of the chest, respectively. Schematic locations of the sternum (left) and spinal column (right) are demarcated at the top of the map. Encircled plus and minus signs denote the location and amplitude of the maximum and minimum. Positive (solid in gray area), negative (dashed) and zero integral contour lines (dotted) are additionally indicated. The incremental step between positive and negative contour lines is linear and shown in mVms below the map under the extreme amplitudes. The integral map demonstrates right superiorly oriented electromotives forces during the initial part of this CCW typical Fl wave episode.