Steady state electron heat transport of FTU high density plasmas (〈ne〉lin≈0.45–1 1020 m−3) during Electron Cyclotron Resonance Heating (ECRH) are compared to predictions of a model based on the assumption of a threshold gradient length, LTc, in the electron temperature Te beyond which electron thermal conductivity, χe, switches from low to high values. The model accounts for the stiffness of Te slope observed in FTU plasmas heated with quite different radial shapes of the ECRH power deposition profile. These profiles are achieved by toroidal field tuning and steering two gaussian beams delivering up to 850 kW to the plasma in a radial position, ρ, ranging from ρ≈0.25 to ρ≈0.5. Plasma response is modelled by assuming the electron conductivity as χe=χe0+αTe3/2 (1/LT−1/LTc)1/2; here Te3/2 reflects the gyro-Bohm assumption, χe0 represents the heat transport for LT>LTc while α, the so-called stiffness coefficient, is adjusted to cope with the observed experimental data. The term (1/LT−1/LTc)1/2 which sets in f...