They are related but different concepts. The value of a company is equal to the discounted value of its future cash flows. If rates go up, that means a higher return can be had for zero risk, which means all cash coming in the future at more than zero risk is now worth less. There is a second term other than risk free rate in the discounting equation which is related to capital structure. So, amount and cost of debt does impact valuation (though there is some debate and theory that makes my statement not quite true), but it is not the only factor.