Common source of miscalculation and misclassification of P-wave negativity and P-wave terminal force in lead V1.

•Misplacement, especially high placement, of precordial electrodes is common.•High placement results in a more than three-fold increase of P-wave terminal force.•Deep terminal negativity is also increased by high placement of the V1 electrode.•High placement of the V1 electrode could be a common source of miscalculation.