Determining local epicardial repolarization patterns using open-chest mapping during heating. (A) Schematic representation of a python heart with superimposed local electrograms recorded with the multi-electrode grid. (B) Local electrograms from the left (a) and right (b) sides of the ventricle at different temperatures. Note that the time to repolarization (indicated by the solid circle) shortens upon heating. (C) Repolarization maps before (left) and after (right) heating showing the change in repolarization sequence. (D) Scatter diagram showing the correlation between the direction of the repolarization gradient and the electrical vector of the T-wave (n = 5). LA, left atrium; RA, right atrium.