  We investigate QCD amplitudes with massive quarks computed in the
four-dimensional helicity scheme (FDH) and dimensional reduction at NNLO and
describe how they are related to the corresponding amplitudes computed in
conventional dimensional regularization. To this end, the scheme dependence of
the heavy quark and the velocity-dependent cusp anomalous dimensions is
determined using soft-collinear effective theory. The results are checked
against explicit computations of massive form factors in FDH at NNLO. Our
results complete the description of the scheme dependence of QCD amplitudes at
NNLO.
