A system, comprising: a neuromodulation catheter comprising- an elongated shaft having a distal portion and a proximal portion, wherein the distal portion is configured to be positioned at a target site in a blood vessel of a human patient; and a plurality of electrodes spaced along the distal portion of the shaft; and a controller configured to be communicatively coupled to the electrodes, wherein the controller is further configured to- detect initial vessel impedance using one or more of the electrodes; apply a first stimulus at and/or proximate to the target site within the blood vessel; detect, via at least one of the electrodes, vessel impedance resulting from the first stimulus to determine a pre-neuromodulation impedance; determine a change in pre-neuromodulation impedance from the initial impedance and the pre-neuromodulation impedance; deliver neuromodulation energy to the target site within the blood vessel of the human patient via the distal portion of the shaft; detect vessel impedance after neuromodulation using one or more of the electrodes; apply a second stimulus at and/or proximate to the target site within the blood vessel after delivering the neuromodulation energy; detect, via at least one of the electrodes, vessel impedance resulting from the second stimulus to determine a post-neuromodulation impedance; determine a change in post-neuromodulation impedance from the impedance after neuromodulation and the post-neuromodulation impedance; and assess efficacy of the neuromodulation based at least in part on the comparison of the change in pre-neuromodulation impedance and the change in post-neuromodulation impedance. a neuromodulation catheter comprising- an elongated shaft having a distal portion and a proximal portion, wherein the distal portion is configured to be positioned at a target site in a blood vessel of a human patient; and a plurality of electrodes spaced along the distal portion of the shaft; and a controller configured to be communicatively coupled to the electrodes, wherein the controller is further configured to- detect initial vessel impedance using one or more of the electrodes; apply a first stimulus at and/or proximate to the target site within the blood vessel; detect, via at least one of the electrodes, vessel impedance resulting from the first stimulus to determine a pre-neuromodulation impedance; determine a change in pre-neuromodulation impedance from the initial impedance and the pre-neuromodulation impedance; deliver neuromodulation energy to the target site within the blood vessel of the human patient via the distal portion of the shaft; detect vessel impedance after neuromodulation using one or more of the electrodes; apply a second stimulus at and/or proximate to the target site within the blood vessel after delivering the neuromodulation energy; detect, via at least one of the electrodes, vessel impedance resulting from the second stimulus to determine a post-neuromodulation impedance; determine a change in post-neuromodulation impedance from the impedance after neuromodulation and the post-neuromodulation impedance; and assess efficacy of the neuromodulation based at least in part on the comparison of the change in pre-neuromodulation impedance and the change in post-neuromodulation impedance.