Systems and methods for assessing efficacy of renal neuromodulation therapy

A neuromodulation system, comprising:

• a neuromodulation catheter having a proximal portion and a distal portion configured for intravascular delivery to a renal blood vessel of a human patient, wherein the distal portion is configured to (a) deliver neuromodulation energy at a target site in the renal blood vessel and (b) detect an impedance in the renal blood vessel;
• and
• a controller configured to be communicatively coupled to the neuromodulation catheter and adapted to:
• determine, using the neuromodulation catheter, a transient change in the impedance in the renal blood vessel resulting from an introduction of a bolus of an indicator fluid into the renal blood vessel upstream of the target site relative to a direction of blood flow in the renal blood vessel, the bolus having a known volume;
• determining a measurement related to a blood flow rate through the renal blood vessel based on the transient change in the impedance and the known volume;
• correcting the measurement related to the blood flow rate for at least one of a current leakage into surrounding tissue of the renal blood vessel or a non-homogeneity of an impedance field across a cross-sectional area of the renal blood vessel, wherein correcting the measurement is based on a flow rate offset and a flow rate gain term;
• compare the measurement to a baseline measurement related to the blood flow rate through the renal blood vessel;
• and
• based on the comparison, determine a change in the blood flow rate through the renal blood vessel resulting from neuromodulation energy delivered via the neuromodulation catheter.

A method for assessing efficacy of neuromodulation therapy, the method comprising:

• positioning a distal portion of a neuromodulation catheter at a target site within a renal artery of a human patient, wherein the distal portion of the neuromodulation catheter is configured to deliver neuromodulation energy;
• injecting a first bolus of an indicator fluid into the renal artery, wherein the indicator fluid has a resistivity that is higher than a resistivity of blood in the renal artery, the first bolus having a first known volume;
• determining a first transient change in an impedance in the renal artery resulting from movement of the first bolus of the indicator fluid past the distal portion of the neuromodulation catheter;
• delivering neuromodulation energy at the target site with the neuromodulation catheter;
• injecting, after delivery of the neuromodulation energy, a second bolus of the indicator fluid into the renal artery, the second bolus having a second known volume;
• determining a second transient change in the impedance in the renal artery resulting from movement of the second bolus of the indicator fluid past the distal portion of the neuromodulation catheter;
• comparing the first and second transient changes in the impedance to assess the efficacy of the delivered neuromodulation energy,
• wherein comparing the first and second transient changes in the impedance includes determining at least one of an increase in a flow rate of the blood in the renal artery or a decrease in vascular resistance of the renal artery, and
• correcting the determined increase in the flow rate of the blood for at least one of a current leakage into surrounding tissue of the renal blood vessel or a non-homogeneity of an impedance field across a cross-sectional area of the renal blood vessel, wherein correcting the determined increase in the flow rate is based on a flow rate offset and a flow rate gain term.