Systems and methods for treating cardiac arrhythmia
Apparatus for monitoring activation in a heart comprises a probe ( 100 ), a plurality of electrodes ( 102 ) supported at respective electrode positions on the probe and each arranged to contact a respective detection position on the heart. Each of the electrodes ( 102 ) is arranged to detect electrical potential at the respective detection position during movement of a series of activation wavefronts across the heart and to produce a respective electrode signal. Processing means is arranged to analyse the electrode signals to: identify pairs of the electrode signals between which there is a degree of Granger causality; define a causality vector between the electrode positions of each of the pairs of electrodes; identify a potential driver location; and analyse the direction of a plurality of the causality vectors around the potential driver position to generate an indicator of the presence of a driver at the potential driver location.
1 . An apparatus for monitoring activation in a heart during movement of a series of activation wavefronts across the heart, the apparatus comprising a probe, a plurality of electrodes supported at respective electrode positions on the probe and each configured to contact a respective detection position on the heart, wherein each of the electrodes is configured to detect electrical potential at the respective detection position during said movement of said series of activation wavefronts across the heart and to produce a respective electrode signal, and a processor configured to analyse the electrode signals to:
define a threshold value of Granger causality;
identify pairs of the electrode signals between which there is a Granger causality over the defined threshold value;
define a Granger causality vector between the two electrode positions of each of the pairs of electrodes;
define a plurality of regions of the heart;
analyse the Granger causality vectors in the plurality of regions of the heart to determine an organization measure for each of the regions, and to select one of the plurality of regions based on the organization measure;
identify a potential driver location within said one of the plurality of regions; and
analyse a direction of a plurality of the Granger causality vectors around the potential driver position thereby to generate an indicator of a presence of a driver at the potential driver location;
wherein the organization measure includes a measure of the number of said pairs of electrodes within said one of the regions that have a Granger causality over the defined threshold; and
wherein the processor is arranged to analyse the direction of a plurality of the Granger causality vectors around the potential driver location by defining a relative position vector for each of the pairs of electrodes, related to a relative position of at least one of the pair of electrodes and the potential driver position, and, for each pair of electrodes, forming a vector cross product between the Granger causality vector and the relative position vector.
2 . The apparatus according to claim 1 wherein the processor is arranged to identify the pairs of the electrodes using a multi-variate auto-regression model.
3 . The apparatus according to claim 1 wherein the processor is arranged to analyse the direction of a plurality of the Granger causality vectors around the potential driver location by: defining a relative position vector for each of the pairs of electrodes, related to a relative position of at least one of the pair of electrodes and the potential driver position, and, for each pair of electrodes, forming a vector cross product between the Granger causality vector and the relative position vector.
4 . The apparatus according to claim 3 wherein the processor is arranged to sum the vector cross products to generate the indicator.
5 . The apparatus according to claim 1 wherein the organization measure includes a measure of at least one dominant frequency in the electrode signals.