Implantable pressure monitor

1. An implantable pressure monitor comprising:

a substantially rigid chip including:

a proximal end and a distal end;

pressure sensors exposed on a first surface of the chip in a sensor region of the distal end;

signal processing circuitry receiving pressure-indicative signals from the sensors and producing pressure-indicative output signals; and

a chip electrical connector in the proximal end communicating the output signals;

a substantially rigid substrate that:

is spaced apart from the chip;

faces the first surface of the chip;

is connected to the chip electrical connector in the chip's proximal end by a substrate electrical connector;

defines an aperture positioned over the sensor region of the chip's distal end, thereby exposing the pressure sensors; and

covers the distal end of the chip except for the sensor region;

a flexible filler material located throughout space between the chip and the substrate except beneath the aperture, thereby leaving the pressure sensors exposed, such that (a) the flexible filler material connects the chip to the substrate, and (b) the distal end of the chip is connected to the substrate by only the flexible filler material;

a wire that:

extends from the substrate;

is electrically connected to the substrate electrical connector;

communicates the output signals; and

is not connected to the chip; and

a biocompatible sheath that encapsulates the chip, substrate, filler, and wire, and is sufficiently flexible to transmit pressure exerted on the sheath exterior through the sheath.

2. The implantable pressure monitor of claim 1 , wherein the sheath has a curved shape to reduce or eliminate hydrodynamic forces.

3. The implantable pressure monitor of claim 1 , wherein the substantially rigid substrate extends proximally from the chip to a proximal end which comprises an anchor.

4. The implantable pressure monitor of claim 3 , wherein the anchor comprises a transversely extending flange that forms suture wings.

5. The implantable pressure monitor of claim 1 , further comprising a holder that fixedly receives the chip and the substantially rigid substrate and extends proximally to a proximal end which comprises an anchor.

6. The implantable pressure monitor of claim 5 , wherein the holder further comprises a distal end cap protecting the chip and the substantially rigid substrate.

7. The implantable pressure monitor of claim 1 , wherein the flexible filler material comprises silicone.

8. The implantable pressure monitor of claim 1 , wherein the flexible filler material holds the chip and the substrate together in a fixed relationship.

9. The implantable pressure monitor of claim 1 , wherein the substantially rigid substrate extends distally from the chip to a distal end which comprises a barrier wall protecting a distal end of the chip.

10. The implantable pressure monitor of claim 9 , wherein the barrier wall forms an end cap at the distal end of the chip.

11. The implantable pressure monitor of claim 10 , wherein the barrier wall extends in a direction substantially perpendicular to a plane of the substrate and to a height such that a top of the barrier wall is at or above a top of the chip.

12. The implantable pressure monitor of claim 9 , wherein the substantially rigid substrate further extends distally from the barrier wall to a tapered front portion.

13. The implantable pressure monitor of claim 1 , wherein the sheath comprises a one-piece, seamless silicone covering.

14. The implantable pressure monitor of claim 13 , wherein the flexible filler material comprises silicone.

15. The implantable pressure monitor of claim 1 , wherein the substrate is sufficiently rigid such that it cannot be folded or rolled up.

16. The implantable pressure monitor of claim 1 , wherein the substrate is sufficiently rigid to protect the pressure sensors from damage as a consequence of contact with a surgical instrument during implantation and from mechanical damage during use.

17. The implantable pressure monitor of claim 1 , wherein the substrate is sufficiently rigid to avoid twisting of the chip due to turbulent blood flow.

18. The implantable pressure monitor of claim 1 , wherein the substrate is rigid.

19. The implantable pressure monitor of claim 1 , wherein the substrate is mechanically inflexible.

20. A method of monitoring pressure, the method comprising:

providing an implantable pressure monitor comprising:

a substantially rigid chip including:

a proximal end and a distal end;

pressure sensors exposed on a first surface of the chip in a sensor region of the distal end;

signal processing circuitry receiving pressure-indicative signals from the sensors and producing pressure-indicative output signals; and

a chip electrical connector in the proximal end communicating the output signals;

a substantially rigid substrate that:

is spaced apart from the chip;

faces the first surface of the chip;

is connected to the chip electrical connector in the chip's proximal end by a substrate electrical connector;

defines an aperture positioned over the sensor region of the chip's distal end, thereby exposing the pressure sensors; and

covers the distal end of the chip except for the sensor region;

a flexible filler material located throughout space between the chip and the substrate except beneath the aperture, thereby leaving the pressure sensors exposed, such that (a) the flexible filler material connects the chip to the substrate, and (b) the distal end of the chip is connected to the substrate by only the flexible filler material;

a wire that:

extends from the substrate;

is electrically connected to the substrate electrical connector;

communicates the output signals; and

is not connected to the chip; and

a biocompatible sheath that encapsulates the chip, substrate, filler, and wire, and is sufficiently flexible to transmit pressure exerted on the sheath exterior through the sheath;

positioning the monitor in a space in which pressure is to be monitored such that the pressure sensors of the monitor are exposed to the pressure;

conveying power to the monitor, thereby causing the monitor to operate;

receiving from the monitor the pressure-indicative output signals; and

storing the pressure-indicative output signals.