METHOD AND SYSTEM FOR EVALUATING STABILITY OF CARDIAC PROPAGATION RESERVE

A method of determining the susceptibility to ventricular arrhythmias in a subject, comprises the steps of: (a) collecting (e.g., by by surface EKG or intracardiac EKG) at least one QT and DI interval data set from the subject during a stage of gradually increasing heart rate or a stage of gradually decreasing heart rate; (b) determining (e.g., by applying low- and high pass filtering) low-frequency QT-DI interval trends and high-frequency QT-DI fluctuation signals in said at least one QT and DI interval data set; (c) finding a plurality of correlated and anti-correlated portions between said high-frequency QT-DI fluctuation signals; (d) determining corresponding regression lines for said correlated and anti-corelated portions; (e) finding a plurality of (or in some embodiments all) steady state QT-DI points designated by intersections between said low frequency QT-DI trends and said corresponding regression lines; (f) fitting action potential durations computed from a rate dependent reaction-diffusion model to corresponding ones of said steady state QT-DI points to give (i) a model excitation threshold and (ii) a minimal level of refractoriness at a plurality of (or in some embodiments all of) said steady state QT-DI points; (g) at the steady state QT-DI point corresponding to the highest heart rate in said QT and DI interval data set, determining the difference between said minimal level of refractoriness and a model critical excitation threshold for a stable solitary pulse corresponding to the rate dependent reaction diffusion model of step (f) to give a reserve of refractoriness (RoR); (h) fitting action potential durations computed from a rate dependent reaction-diffusion model to said correlated and anti-correlated portions to give a rate of adaptation of each model excitation threshold to a corresponding steady state value at a plurality of (or in some embodiments all of) said steady state QT-DI points; (i) at the steady state QT-DI point corresponding to the highest heart rate in said QT and DI interval data set, determining the inverse of said rate of adaptation to give a reserve of memory (RoM); (j) combining said reserve of refractoriness (RoR) and said reserve of memory (RoM) to produce a metric of stability-of-propagation reserve (SoPR) in said subject, a higher value of SoPR indicating lower susceptibility to ventricular arrhythmias in said subject. Systems and apparatus for carrying out the method are also described. L'invention concerne un