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Abstract

Implantable medical devices (IMDs) for monitoring signs of acute or chronic cardiac heart failure by measuring cardiac blood pressure and mechanical dimensions of the heart and providing multi-chamber pacing optimized as a function of measured blood pressure and dimensions are disclosed. The dimension sensor or sensors comprise at least a first sonomicrometer piezoelectric crystal mounted to a first lead body implanted into or in relation to one heart chamber that operates as an ultrasound transmitter when a drive signal is applied to it and at least one second sonomicrometer crystal mounted to a second lead body implanted into or in relation to a second heart chamber that operates as an ultrasound receiver. The ultrasound receiver converts impinging ultrasound energy transmitted from the ultrasound transmitter through blood and heart tissue into an electrical signal. The time delay between the generation of the transmitted ultrasound signal and the reception of the ultrasound wave varies as a function of distance between the ultrasound transmitter and receiver which in turn varies with contraction and expansion of a heart chamber between the first and second sonomicrometer crystals. One or more additional sonomicrometer piezoelectric crystal can be mounted to additional lead bodies such that the distances between the three or more sonomicrometer crystals can be determined. In each case, the sonomicrometer crystals are distributed about a heart chamber such that the distance between the separated ultrasound transmitter and receiver crystal pairs changes with contraction and relaxation of the heart chamber walls.

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First Claim