Patent ID: 7937150

Claim:
An implantable medical device (IMD), comprising: a canister comprising a case electrode, wherein the case electrode provides a first local electrode for use in performing quadripolar measurements of transthoracic impedance; a header coupled to the canister for receiving at least one lead, wherein the canister and the header form at least a part of a package of the IMD; a first distal electrode formed on a surface of the at least one lead; a second distal electrode formed on a surface of the at least one lead; a second local electrode formed to rest on a surface of a lead, the second local electrode being positioned proximal to the first and second distal electrodes and positioned in close proximity to the canister, wherein the second local electrode is positioned adjacent to the header such that the second local electrode is prevented from shorting to a portion of the package due to flexing of the lead, one of the first local electrode and the second local electrode together with one of the first distal electrode and the second distal electrode being a first independent set of electrodes defining a path for current stimulation, a different one of the first local electrode and the second local electrode together with a different one of the first distal electrode and the second distal electrode being a second independent set of electrodes defining an impedance measuring path; and quadripolar transthoracic impedance measurement circuitry coupled to the first local electrode, the first distal electrode, the second distal electrode, and the second local electrode, the circuitry configured to perform quadripolar measurements of transthoracic impedance using the electrodes.