Patent ID: 7848822

Claim:
An apparatus, comprising: a fully implantable intravascular cardiac lead including a proximal portion and a distal portion, the proximal portion adapted to be coupled to an electronics unit of an implantable medical device, the distal portion adapted to be located within a chamber of a heart; and a force sensor associated with the distal portion of the fully implantable intravascular cardiac lead, the force sensor including: a displacement sensor adapted to sense a displacement of a portion of the heart during a heart movement, the displacement sensor including a first portion movable with respect to a second portion along an axial direction of the lead and in response to the displacement of the portion of the heart, axial movement of the first portion with respect to the second portion being representative of the displacement of the portion of the heart, the displacement sensor being configured to provide an output displacement signal indicative of the displacement sensed; and a contractile structure separate from the displacement sensor, the contractile structure being configured to axially expand or axially contract an axial distance representative of the axial movement of the first portion of the displacement sensor with respect to the second portion, wherein the force sensor is configured to provide a sensed force signal indicative of a force with which at least the portion of the heart moves during the heart movement, the force sensor configured to determine the force as a function of the distance that the contractile structure axially expands or axially contracts, the force sensor being configured to communicate the sensed force signal to the electronics unit.