METHODS AND SYSTEMS FOR WAVELENGTH MAPPING CARDIAC FIBRILLATION AND OPTIMIZING ABLATION LESION PLACEMENT
A system that executes a process for mapping cardiac fibrillation and optimizing ablation treatments. The process, in some embodiments, includes: positioning a two dimensional electrode array to several locations in a patient's heart and at each location, obtaining a conduction velocity and a cycle length measurement from at least two local signals in response to electrical activity in the cardiac tissue. In some embodiments, a regional wavelength is calculated by multiplying the local conduction velocity with the local minimum cycle length. The system can then create a wavelength distribution map that identifies the location of the drivers in the heart. In certain embodiments, the system uses variability of conduction velocity and cycle length in an area to determine the driver type. In some embodiments, the system calculates average distance of drivers to non-conductive tissue boundaries. The system then selects ablation placements that maximize treatment efficacy while minimizing tissue damage.
1 . A method for mapping cardiac fibrillation in a patient, comprising:
(a) positioning a two dimensional electrode array at a first location of the patient's heart, wherein the two dimensional electrode array comprises at least a first electrode pair and a second electrode pair, wherein the first electrode pair is configured to detect a first local signal, and wherein the second electrode pair is configured to detect a second local signal;
(b) registering the location of the first electrode pair and the second electrode pair, wherein the first electrode pair and the second electrode pair is separated by a distance;
(c) obtaining a first conduction velocity measurement from the first local signal and the second local signal in response to electrical activity in the cardiac tissue, wherein the conduction velocity measurement is determined from a time difference between the first and the second local signals and the distance between the first electrode pair and the second electrode pair;
(d) obtaining a first cycle length measurement from the first local signal in response to the electrical activity in the cardiac tissue, wherein the first cycle length measurement is determined by a time difference between a first excitation and a second excitation detected in the first local signal; and
(e) calculating a first regional wavelength by multiplying the first conduction velocity measurement obtained in (c) and the first cycle length measurement obtained in (d).
2 . The method of claim 1 , further comprising:
moving the two dimensional electrode array to a second location of the patient's heart to obtain a second conduction velocity measurement and a second cycle length measurement; and
calculating a second regional wavelength by multiplying the second conduction velocity measurement and the second cycle length measurement.
3 . The method of claim 2 , wherein the second location of the patient's heart does not overlap with the first location of the patient's heart.
4 . The method of claim 2 , further comprising:
creating a wavelength distribution map for the patient's heart based on at least the first and the second regional wavelength.
5 . The method of claim 3 , further comprising:
identifying one or more driver locations based on the wavelength distribution map.
6 . The method of claim 1 , wherein the first local signal is obtained by a difference in electrical activity obtained from the first electrode and the second electrode in the first electrode pair.
7 . The method of claim 1 , wherein obtaining the conduction velocity measure further comprises:
identifying a first wave activation time at the first electrode pair, a second wave activation time at the second electrode pair, and a set of additional wave activation times at one or more electrode pairs neighboring the first electrode pair;
determining a first-to-second time interval based on the time difference between the first wave activation time and the second wave activation time;
determining a set of time intervals based on the time difference between the first wave activation time and the set of additional wave activation times at one or more electrode pairs neighboring the first electrode pair;
wherein the first-to-second time interval is the longest comparing to the set of time intervals; and
wherein the vector of the conduction velocity is in the direction from the first electrode pair to the second electrode pair.
8 . A method for optimizing ablation lesion placement in a patient's heart, comprising:
identifying one or more drivers and one or more driver locations in an area of the patient's heart based on a tissue property distribution map of a portion of the patient's heart;
determining a conduction velocity variability associated with a first region in the area of the patient's heart, wherein the conduction velocity variability is based on a standard deviation in conduction velocity measurements obtained across at least two electrical waves;
determining a cycle length variability associated with a first region in the area of the patient's heart, wherein the cycle length variability is based on a standard deviation in cycle length measurements obtained across the at least two electrical waves;
identifying a driver type for the one or more drivers based on the conduction velocity variability and the cycle length variability; and
estimating an optimal ablation lesion placement based on the driver type and the one or more driver locations.
9 . The method of claim 7 , wherein the driver type is a stationary rotor if the conduction velocity variability and the cycle length variability are, respectively, below a threshold.
10 . The method of claim 7 , wherein the driver type is a moving driver if the conduction velocity variability and the cycle length variability are, respectively, above a threshold.
11 . The method of claim 8 , further comprising identifying the center of the stationary rotor.
12 . The method of claim 11 , wherein the center of the stationary rotor is identified by the region of the rotor with the lowest conduction velocity.
13 . The method of claim 9 , wherein estimating the optimal ablation lesion placement includes projecting an ablation to the center of the stationary rotor.
14 . The method of claim 9 , wherein estimating the optimal ablation lesion placement includes isolating the stationary rotor by an encircling ablation lesion.
15 . The method of claim 10 , further comprising calculating an average travel distance of the moving driver to a non-conductive tissue boundary to determine an optimal location for the ablation lesion placement.
16 . The method of claim 15 , wherein the non-conductive tissue boundary is a potential ablation lesion line.
17 . The method of claim 15 , wherein estimating the optimal ablation lesion placement further comprising selecting an ablation lesion line that results in the smallest average travel distance.
18 . The method of claim 8 , wherein the tissue property distribution map of a portion of the patient's heart includes a wavelength distribution map, a cycle length distribution map, or a conduction velocity distribution map.
19 . A system for optimizing ablation lesion placement in a patient's heart, comprising:
an electrode array system having at least a first electrode pair and a second electrode pair, wherein the first electrode pair is configured to detect a first local signal, and wherein the second electrode pair is configured to detect a second local signal, wherein the first electrode pair and the second electrode pair are separated by a distance, and wherein the electrode array system is configured to obtain one or more measurements from at least the first local signal and the second local signal in response to electrical activity in the cardiac tissue substrate;
a processor to register the location of at least the first electrode pair and the second electrode pair of the electrode array system, to process the one or more measurements to obtain at least a first conduction velocity measurement and a
first cycle length measurement, wherein the first conduction velocity measurement is determined from a time difference between the first and the second local signals and the distance between the first electrode pair and the second electrode pair, and wherein the first cycle length measurement is determined by a time difference between a first excitation and a second excitation detected in the first local signal, and to calculate at least a first regional wavelength by multiplying the first conduction velocity measurement with the first cycle length measurement; and
a storage device to store data and executable instructions to be used by the processor.