An implantable medical device (100, 200), IMD (100, 200), for operating in a modified impedance mode, comprising: a stimulation unit to provide an electrical stimulation signal through a lead operatively coupled to said IMD (100, 200); a controller comprising a signal detection unit to receive an indication selected from the group consisting of (a) an indication of the presence of a coupled energy on said lead and (b) an indication of the future presence of a coupled energy on said lead; and an impedance unit to modify an impedance of said lead based upon said indication received by said signal detection unit; wherein the signal detection unit comprises at least one of: a frequency count unit to perform at least one of a frequency division and a frequency count to determine whether said coupled energy is present on said lead; a bandpass filter comprising at least one of a highpass filter and a lowpass filter to determine whether said coupled energy is present on said lead; an envelope comparator circuit to determine whether said coupled energy is present on said lead; and a thermal sensor to determine whether said coupled energy is present on said lead; and characterized in that said impedance unit comprises: more than one of a capacitive impedance, an inductive impedance, a resistive impedance, a short-circuit, an open circuit; and a switching network comprising a plurality of switches to switch between more than one of said capacitive impedances, inductive impedances, and resistive impedances to modify said impedance of said lead and a switch controller to control the switching of said switches and capable of switching more than one of said capacitive impedance, inductive impedance, resistive impedance, said open circuit, and said short circuit to modify said impedance of said lead. a stimulation unit to provide an electrical stimulation signal through a lead operatively coupled to said IMD (100, 200); a controller comprising a signal detection unit to receive an indication selected from the group consisting of (a) an indication of the presence of a coupled energy on said lead and (b) an indication of the future presence of a coupled energy on said lead; and (a) an indication of the presence of a coupled energy on said lead and (b) an indication of the future presence of a coupled energy on said lead; and an impedance unit to modify an impedance of said lead based upon said indication received by said signal detection unit; wherein the signal detection unit comprises at least one of: a frequency count unit to perform at least one of a frequency division and a frequency count to determine whether said coupled energy is present on said lead; a bandpass filter comprising at least one of a highpass filter and a lowpass filter to determine whether said coupled energy is present on said lead; an envelope comparator circuit to determine whether said coupled energy is present on said lead; and a thermal sensor to determine whether said coupled energy is present on said lead; and characterized in that said impedance unit comprises: more than one of a capacitive impedance, an inductive impedance, a resistive impedance, a short-circuit, an open circuit; and a switching network comprising a plurality of switches to switch between more than one of said capacitive impedances, inductive impedances, and resistive impedances to modify said impedance of said lead and a switch controller to control the switching of said switches and capable of switching more than one of said capacitive impedance, inductive impedance, resistive impedance, said open circuit, and said short circuit to modify said impedance of said lead. a frequency count unit to perform at least one of a frequency division and a frequency count to determine whether said coupled energy is present on said lead; a bandpass filter comprising at least one of a highpass filter and a lowpass filter to determine whether said coupled energy is present on said lead; an envelope comparator circuit to determine whether said coupled energy is present on said lead; and a thermal sensor to determine whether said coupled energy is present on said lead; and characterized in that said impedance unit comprises: more than one of a capacitive impedance, an inductive impedance, a resistive impedance, a short-circuit, an open circuit; and a switching network comprising a plurality of switches to switch between more than one of said capacitive impedances, inductive impedances, and resistive impedances to modify said impedance of said lead and a switch controller to control the switching of said switches and capable of switching more than one of said capacitive impedance, inductive impedance, resistive impedance, said open circuit, and said short circuit to modify said impedance of said lead. more than one of a capacitive impedance, an inductive impedance, a resistive impedance, a short-circuit, an open circuit; and a switching network comprising a plurality of switches to switch between more than one of said capacitive impedances, inductive impedances, and resistive impedances to modify said impedance of said lead and a switch controller to control the switching of said switches and capable of switching more than one of said capacitive impedance, inductive impedance, resistive impedance, said open circuit, and said short circuit to modify said impedance of said lead.