US Patent 7720534 Transthoracic impedance measurement in a subcutaneous device

A subcutaneous implantable cardioverter-defibrillator is disclosed which has an electrically active canister which houses a source of electrical energy, a capacitor, and operational circuitry that senses the presence of potentially fatal heart rhythms. At least one subcutaneous electrode that serves as the opposite electrode from the canister is attached to the canister via a lead system. Cardioversion-defibrillation energy is delivered when the operational circuitry senses a potentially fatal heart rhythm. There are no transvenous, intracardic, or epicardial electrodes. A method of subcutaneously implanting the cardioverter-defibrillator is also disclosed as well as a kit for conducting the method.