“…Since the QRST complexes overshadow the f waves, it is highly desirable to extract a connected f -wave signal containing more samples for characterization than what is contained in the TQ intervals, especially in short RR intervals which are rather frequent in AF (Sörnmo, Petrėnas, Laguna & Marozas 2018). Different signal processing principles have been explored for f -wave extraction which may be categorized as follows: average beat subtraction and variants (Stridh & Sörnmo 2001, Lemay, Vesin, van Oosterom, Jacquemet & Kappenberger 2007, Dai, Jiang & Li 2013, principal component analysis (Castells, Mora, Rieta, Moratal-Pérez & Millet 2005, Langley, Stridh, Rieta, Millet, Sörnmo & Murray 2006, Alcaraz & Rieta 2008, interpolation and singular spectral analysis (Sassi, Corino & Mainardi 2009), independent component analysis (Rieta, Castells, Sánchez, Zarzoso & Millet 2004, Phlypo, Zarzoso & Lemahieu 2010, adaptive filtering using an echo state network (Petrėnas, Marozas, Sörnmo & Lukosevicius 2012), extended Kalman filtering (Kheirati Roonizi & Sassi 2017), and diffusion geometry (Malik, Reed, Wang & Wu 2017).…”