Endocardial implantable cardiac leads are disclosed for applying electrical stimulation to and / or sensing electrical activity of the heart at one or more distal
electrode positioned at a cardiac
implantation site within a cardiac vessel adjacent to and at a desired orientation to the left
ventricle or atrium of the heart. The distal
electrode(s) is supported by a tubular
electrode support having a
diameter large enough to bear against the
blood vessel wall and a support lumen that allows blood to flow through it. A retention
stent extends proximally from a distal
stent end fixed to the tubular electrode support to a proximal
stent end. After advancement to the cardiac
implantation site employing a lead delivery mechanism, the retention stent is expandable from a collapsed stent state in which the outer
diameter of the retention stent is less than the inner
diameter of the vessel to an expanded stent state. The expanded stent is lodged against the
blood vessel wall and inhibits movement of the stent and distal electrode support. The expanded stent lumen is aligned with the electrode support lumen for allowing blood to flow through the aligned electrode support lumen and expanded stent lumen. The retention stent may take any of the known forms that can be introduced in the collapsed stent state within an introducer lumen or mounted to an introducer and can either self-expand upon release in the
blood vessel or be mechanically expanded within the blood vessel.