Variability in body conductivities modulates QRS amplitudes. Differences in the diffusion of electrical potential across the human torso affect the magnitudes of BSPs, without significantly altering their spatial pattern (left panel; BSP distributions shown at time for R-peak in lead II). This is translated in inversely proportional QRS amplitudes to body conductivities, and increased R-wave progression (right panel). Dashed grey ECG traces: baseline conditions; solid red and blue ECG traces: increased and decreased torso conductivity, respectively. Symbols indicate maximum wave amplitudes under variability in torso conductivity (same colour code). Simulated ECG grid resolution: 40 ms/0.1 mV.