System and method for locating and identifying the functional nerves innervating the wall of arteries and catheters for same
System and method for locating and identifying nerves innervating the wall of arteries such as the renal artery are disclosed. The present invention identifies areas on vessel walls that are innervated with nerves; provides indication on whether energy is delivered accurately to a targeted nerve; and provides immediate post-procedural assessment of the effect of energy delivered to the nerve. The method includes at least the steps to evaluate a change in physiological parameters after energy is delivered to an arterial wall; and to determine the type of nerve that the energy was directed to (none, sympathetic or parasympathetic) based on the evaluated results. The system includes at least a device for delivering energy to the wall of blood vessel; sensors for detecting physiological signals from a subject; and indicators to display results obtained using said method. Also provided are catheters for performing the mapping and ablating functions.
1. A method of mapping a parasympathetic renal nerve, comprising the steps of:
a) introducing a catheter into the lumen of a renal artery such that a tip of said catheter contacts a site on an inner wall of said renal artery;
b) measuring one or more physiological parameters to obtain baseline measurements before introducing an electrical current to the site, said physiological parameters are selected from the group consisting of systolic blood pressure, diastolic blood pressure, mean arterial pressure, and heart rate;
c) applying electrical stimulation by introducing said electrical current to the site via the catheter, wherein said electrical current is controlled to be sufficient to elicit changes in said physiological parameters when there is an underlying parasympathetic nerve at the site; and
d) measuring said physiological parameters at a specific time interval after each electrical stimulation, wherein a decrease of said physiological parameters below the baseline measurements after said electrical stimulation would indicate that a parasympathetic renal nerve has been mapped at said site.
2. The method of claim 1 , wherein said catheter is an ablative catheter designed to treat cardiac arrhythmias.
3. The method of claim 1 , wherein said catheter is an ablative catheter designed specifically for mapping renal nerves for ablative procedures.
4. The method of claim 1 , wherein said specific time interval in step (d) is from about 5 seconds to about 2 minutes.
5. The method of claim 1 , wherein said one or more physiological parameters includes said systolic blood pressure, and said decrease in systolic blood pressure is more than 2 mmHg.
6. The method of claim 1 , wherein said one or more physiological parameters includes said diastolic blood pressure, and said decrease in diastolic blood pressure is more than 2 mmHg.
7. The method of claim 1 , wherein said one or more physiological parameters includes said mean arterial pressure, and said decrease in mean arterial pressure is more than 2 mmHg.
8. The method of claim 1 , wherein said one or more physiological parameters includes said heart rate, and said decrease in heart rate is more than 5 beats/min.
9. The method of claim 1 , wherein the electrical current sufficient to elicit changes in the physiological parameters comprises one or more of the following parameters:
(a) voltage of between 2 and 30 volts;
(b) resistance of between 100 and 1000 ohms;
(c) current of between 5 and 40 miliamperes; or
(d) applied between 0.1 and 20 milliseconds.
10. The method of claim 1 , further comprising a step of applying radiofrequency energy through the catheter for ablation of underlying nerve to treat disease caused by systemic renal nerve hyperactivity, wherein said ablation is not applied to the site identified in step (d).
11. A method of mapping a sympathetic renal nerve, comprising the steps of:
a) introducing a catheter into the lumen of a renal artery such that a tip of said catheter contacts a site on an inner wall of said renal artery;
b) measuring one or more physiological parameters to obtain baseline measurements before introducing an electrical current to the site, said physiological parameters are selected from the group consisting of systolic blood pressure, diastolic blood pressure, mean arterial pressure, and heart rate;
c) applying electrical stimulation by introducing said electrical current to the site via the catheter, wherein said electrical current is controlled to be sufficient to elicit changes in said physiological parameters when there is an underlying sympathetic nerve at the site; and
d) measuring said physiological parameters at a specific time interval after each electrical stimulation, wherein an increase of said physiological parameters below the baseline measurements after said electrical stimulation would indicate that a sympathetic renal nerve has been mapped at said site.
12. The method of claim 11 , wherein said catheter is an ablative catheter designed to treat cardiac arrhythmias.
13. The method of claim 11 , wherein said catheter is an ablative catheter designed specifically for mapping renal nerves for ablative procedures.
14. The method of claim 11 , wherein said specific time interval in step (d) is from about 5 seconds to about 2 minutes.
15. The method of claim 11 , wherein said one or more physiological parameters includes said systolic blood pressure, and said increase in systolic blood pressure is more than 4 mmHg.
16. The method of claim 11 , wherein said one or more physiological parameters includes said diastolic blood pressure, and said increase in diastolic blood pressure is more than 1.5 mmHg.
17. The method of claim 11 , wherein said one or more physiological parameters includes said mean arterial pressure, and said increase in mean arterial pressure is more than 3 mmHg.
18. The method of claim 11 , wherein said one or more physiological parameters includes said heart rate, and said increase in heart rate is more than 4 beats/min.
19. The method of claim 11 , wherein the electrical current sufficient to elicit changes in the physiological parameters comprises one or more of the following parameters:
(a) voltage of between 2 and 30 volts;
(b) resistance of between 100 and 1000 ohms;
(c) current of between 5 and 40 miliamperes; or
(d) applied between 0.1 and 20 milliseconds.
20. The method of claim 11 , further comprising a step of applying radiofrequency energy through the catheter to the site identified in step (d) for ablation of said sympathetic renal nerve to treat disease caused by systemic renal nerve hyperactivity.