Fig. 20.5 Baule-McFee lead system. (A) The general construction of the measurement system. (B) Measurement of the x-component of the magnetic heart vector. (C) Measurement of the y-component of the magnetic heart vector. (D) Measurement of the z-component of the magnetic heart vector. Baule-McFee lead system makes a bipolar measurement of the equivalent magnetic dipole of the heart.