Methods and apparatus for intravascularly-induced neuromodulation
Methods and apparatus are provided for intravascularly-induced neuromodulation using a pulsed electric field, e.g., to effectuate irreversible electroporation or electrofusion, necrosis and/or inducement of apoptosis, alteration of gene expression, changes in cytokine upregulation, etc., in target neural fibers. In some embodiments, the intravascular PEF system comprises a catheter having a pair of bipolar electrodes for delivering the PEF, with a first electrode positioned on a first side of an impedance-altering element and a second electrode positioned on an opposing side of the impedance-altering element. A length of the electrodes, as well as a separation distance between the first and second electrodes, may be specified such that, with the impedance-altering element deployed in a manner that locally increases impedance within a patient's vessel, e.g., with the impedance-altering element deployed into contact with the vessel wall at a treatment site within the patient's vasculature, a magnitude of applied voltage delivered across the bipolar electrodes necessary to achieve desired neuromodulation is reduced relative to an intravascular PEF system having similarly spaced electrodes but no (or an undeployed) impedance-altering element. In a preferred embodiment, the impedance-altering element comprises an inflatable balloon configured to locally increase impedance within a patient's vasculature. The methods and apparatus of the present invention may be used to modulate a neural fiber that contributes to renal function.
1. A method for treating a hypertensive human patient, the method comprising:
positioning a catheter within a renal artery of the patient and proximate to renal nerves innervating a kidney of the patient;
transforming an impedance-altering element at a distal portion of the catheter from a low-profile delivery configuration to an expanded treatment configuration within the renal artery; and
inhibiting neural signaling along the renal nerves via thermal energy from a pair of bipolar electrodes carried by the catheter,
wherein the pair of bipolar electrodes are positioned on a shaft of the catheter on opposite ends of and external to the impedance-altering element,
wherein the impedance-altering element is configured to locally increase impedance between the pair of bipolar electrodes during intravascular delivery of the thermal energy, and
wherein inhibiting neural signaling along the renal nerves results in a therapeutically beneficial reduction in blood pressure of the patient.
2. The method of claim 1 wherein inhibiting neural signaling along the renal nerves via thermal energy comprises ablating the renal nerves via electrical energy delivered by the pair of bipolar electrodes.
3. The method of claim 1 wherein inhibiting neural signaling along the renal nerves via thermal energy comprises partially ablating the renal nerves via electrical energy delivered by the pair of bipolar electrodes.
4. The method of claim 1 wherein inhibiting neural signaling along the renal nerves via thermal energy comprises inhibiting neural signaling along the renal nerves via radio frequency (RF) energy delivered by the pair of bipolar electrodes.
5. The method of claim 1 wherein inhibiting neural signaling along the renal nerves via thermal energy comprises inhibiting neural signaling along the renal nerves via pulsed electrical energy delivered by the pair of bipolar electrodes.
6. The method of claim 1 wherein inhibiting neural signaling along the renal nerves via thermal energy comprises at least partially denervating the kidney of the patient.
7. The method of claim 1 wherein the impedance-altering element comprises a balloon, and wherein, in the expanded treatment configuration, the balloon is sized and shaped to temporarily occlude blood flow within the renal artery.
8. The method of claim 1 wherein the impedance-altering element comprises a semi-compliant balloon.
9. The method of claim 1 wherein the impedance-altering element comprises a non-compliant balloon.
10. The method of claim 1 wherein the impedance-altering element comprises an expandable cage, and wherein, in the expanded treatment configuration within the renal artery, the expandable cage does not occlude blood flow within the renal artery.
11. The method of claim 1 wherein the impedance-altering element comprises a balloon, and wherein, in the expanded treatment configuration, the balloon has a length of 5 mm.
12. The method of claim 1 wherein the impedance-altering element comprises a balloon, and wherein, in the expanded treatment configuration, the balloon has a length of 4 mm.
13. The method of claim 1 wherein the impedance-altering element comprises a disc-shaped balloon, and wherein, in the expanded treatment configuration, the balloon is sized and shaped to make substantially tangential wall contact.
14. The method of claim 1 wherein locally increasing impedance further comprises directing the thermal field across a wall of the renal artery between the pair of bipolar electrodes.
15. The method of claim 1 wherein positioning a catheter within a renal artery of the patient comprises intravascularly delivering the catheter to the renal artery over a guidewire.
16. The method of claim 1 wherein positioning a catheter within a renal artery of the patient comprises intravascularly delivering the catheter to the renal artery within a guide catheter.
17. The method of claim 1 , further comprising:
transforming the impedance-altering element from the expanded treatment configuration to the low-profile delivery configuration; and
removing the catheter from the patient after delivering thermal energy via the pair of bipolar electrodes to conclude the procedure.
18. The method of claim 1 , further comprising monitoring a parameter of target tissue and/or non-target tissue within the patient before and during delivery of the thermal energy.
19. The method of claim 18 wherein monitoring a parameter comprises monitoring a temperature of target tissue, and wherein the method further comprises maintaining the target tissue at a desired temperature during delivery of the thermal energy.
20. The method of claim 18 , further comprising altering delivery of the thermal energy in response to the monitored parameter.