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Abstract

An implantable medical device such as a pacemaker or implantable cardioverter defibrillator or stand-alone hemodynamic monitor that uses optical plethysmography responsive to variations in arterial pulse amplitude to detect the hemodynamic status of a patient. A light source and light detector are positioned for a reflected-light configuration on a device housing and coupled to electronic circuitry in the housing via a hermetic feedthrough. In one embodiment, the light source and detector are positioned in a recess in a wall of the device housing and surrounded by an encapsulant. The source and detector are positioned for a reflected-light configuration and are preferably an infrared (IR) LED and photodiode, respectively. The source and detector may be placed in a single recess that is created when the device housing is manufactured. An opaque optical barrier is place between the source and detector, which ensures that no light passes between them without first interacting with the overlying tissue. Light reflected from the source to the detector is modulated by pulsation of blood from vasculature in the surrounding body tissue thus enabling sensing of the strength of a heartbeat.

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First Claim