Errors In Calculating The Epicardial Potential Gradient Field From Unipolar Voltage Measurements During Cardiac Defibrillation

We examined the errors generated when calculating the magnitude of the epicardial potential gradient using voltages recorded from three unipolar electrodes in a fixed triangular geometry on the epicardial surface. The error sensitivity of the gradient calculation increases significantly with decreasing electrode separation and increasing common-mode voltage. For example, a mean error in calculated gradient magnitude of 67% results when measuring a 5 V/cm gradient at 50 V common-mode with 2 mm interelectrode spacing and random 1 % voltage error. Optimization of interelectrode spacing and common-mode voltage to reduce overall error is essential for accurate measurement of low magnitude epicardial gradients.