Measurement of cardiac performance with movement sensors and related methods
Embodiments of the invention are related to implantable devices including movement sensors and related methods for measuring cardiac performance, amongst other things. In an embodiment, the invention includes an implantable electrical stimulation lead. The electrical stimulation lead can include a lead body having a proximal end and a distal end and a sheath defining a central lumen. The lead body can further include an electrical conductor disposed within the central lumen of the sheath. The stimulation lead can further include a stimulation electrode positioned at the distal end of the lead body, the stimulation electrode in electrical communication with the electrical conductor. The electrical stimulation lead can include an flexion sensor coupled to the lead body, the movement sensor configured to generate a signal in response to movement of the lead body. In an embodiment, the invention includes a method of monitoring the condition of a heart failure patient. In an embodiment, the invention includes a method of treating unstable arrhythmia in a patient. Other embodiments are also included herein.
1. An implantable electrical stimulation lead comprising:
a lead body having a proximal end and a distal end, the lead body comprising a sheath defining a central lumen, the lead body further comprising an electrical conductor disposed within the central lumen of the sheath;
a stimulation electrode positioned at the distal end of the lead body, the stimulation electrode in electrical communication with the electrical conductor; and
a first flexion sensor coupled to the lead body at a point closer to the distal end than the proximal end, the first flexion sensor configured to generate an electrical signal in response to flexion of the lead body, wherein the first flexion sensor is a helical sensing element.
2. The implantable electrical stimulation lead of claim 1 , the first flexion sensor comprising a resistive element that changes electrical resistance in response to flexion.
3. The implantable electrical stimulation lead of claim 2 , the resistive element comprising conductive carbon particles.
4. The implantable electrical stimulation lead of claim 2 , the resistive element wrapped around the sheath.
5. The implantable electrical stimulation lead of claim 1 , the lead body comprising a layer of insulation surrounding the electrical conductor, the first flexion sensor disposed on the layer of insulation.
6. The implantable electrical stimulation lead of claim 1 , the sheath having an outside surface, the first flexion sensor disposed on the outside surface.
7. The implantable electrical stimulation lead of claim 1 , the sheath having an inner surface, the first flexion sensor disposed on the inner surface of the sheath.
8. The implantable electrical stimulation lead of claim 1 , further comprising a second flexion sensor coupled to the lead body.
9. The implantable electrical stimulation lead of claim 8 , the second flexion sensor coupled to the lead body at a point between the first flexion sensor and the proximal end of the implantable electrical stimulation lead.
10. The implantable electrical stimulation lead of claim 1 , the sheath comprising a biocompatible material.
11. The implantable electrical stimulation lead of claim 10 , wherein the biocompatible material is one of polysiloxanes, polyethylenes, and polyamides.
12. The implantable electrical stimulation lead of claim 1 , the first flexion sensor comprising a piezoelectric element.
13. The implantable electrical stimulation lead of claim 1 , the first flexion sensor comprising a substrate and a conductive material layer disposed over the substrate.
14. The implantable electrical stimulation lead of claim 13 , the conductive material layer configured to change in resistance in response to the degree to which the conductive material layer is flexed.
15. The implantable electrical stimulation lead of claim 13 , wherein the thickness of the conductive material layer in combination with the substrate is less than about 0.25 mm.
16. The implantable electrical stimulation lead of claim 13 , wherein the thickness of the conductive material layer in combination with the substrate is less than about 0.1 mm.
17. The implantable electrical stimulation lead of claim 1 , wherein the first flexion sensor is an optical flexion sensor.
18. The implantable electrical stimulation lead of claim 17 , the optical flexion sensor comprising an optical fiber with a core surrounded by a cladding layer.
19. The implantable electrical stimulation lead of claim 18 , wherein portions of the cladding layer have been removed to enhance sensitivity of the optical fiber to bending signal loss.
20. The implantable electrical stimulation lead of claim 17 , the optical flexion sensor comprising a bend-enhanced fiber sensor.