A patterned foil sheet heating element has a first discrete region patterned with a first plurality of holes forming multiple conductive ribbons and having a first sheet resistivity. It also has a second discrete region patterned with a second plurality of holes forming multiple conductive ribbons and having a second sheet resistivity. At least some of the multiple conductive ribbons in the first discrete region are in electrical continuity with at least some of the multiple conductive ribbons in the second discrete region, and the first discrete region and the second discrete region both adjoin a first junction strip of the foil heating element. An electrothermal heating assembly may be formed using such a patterned foil sheet sandwiched between two layers of material which may be thermally conductive and electrical insulative.