Fig. 3From: Nonlinear analysis of beat-to-beat variability of action potential time series data identifies dynamic re-entrant substrates in a hypokalaemic mouse model of acquired long QT syndromeExamples of frequency spectra using the Fast Fourier Transform method from a representative heart before (A) or after the application of experimental hypokalaemia (B) and hypokalaemia with 0.1Â mM heptanol (C)Back to article page