The Coulomb-Born approximation is applied to K-shell and L-subshell ionization of Ag and heavier target atoms by electrons above 100 keV. The existing theory is extended to describe the spin asymmetry of the triply differential cross section in the case of polarized electron impact. Particular attention is paid to the dip in the binary peak for L3-subshell ionization at Bethe ridge conditions which is very sensitive to wavefunction effects. Comparison with experimental (e, 2e) data in coplanar geometry verifies the applicability of the Coulomb-Born theory for weakly relativistic target states.