Abstract: A method and apparatus for detecting failure or impending failure of a lead and for providing a warning to a patient or a patient's physician. The impedance of the lead is repeatedly measured and compared with certain impedance limits. If the measured impedance falls outside of these impedance limits, an alarm may be given to the patient, or a warning may be given to the patient's physician.

Abstract: Various endocardial lead assemblies are disclosed that may be particularly useful for placement within the coronary sinus. One lead assembly includes an open-ended electrode that may be implanted in a patient by passing it along a previously implanted stylet. Another disclosed embodiment combines an open-ended electrode with one or more flow passages that improve blood flow through the body vessel in the area of the implanted electrode. Yet another disclosed embodiment uses an electrode that has flow passages but no opening. This electrode provides improved blood flow in the area of the electrode but may be implanted using conventional methods.