“…All included papers can be considered as a truthful basis of related works to this study; therefore, a detailed list of embedded classifiers and input features is further reviewed: - Support vector machine (SVM) classifiers are input with 47 features from the statistical and morphological rhythm representation [ 24 ]; 33 features expressive to the signal power, spectrum, entropy, RR intervals and P-waves [ 25 ]; and 61 features from the time-frequency ECG representation, both average and variability of RR intervals, and the average beat morphology [ 26 ];
- Linear and quadratic discriminant classifiers are input with a set of 122 RR-interval features from their time domain, frequency domain and distribution (histogram) representations [ 27 ] and 44 features measured by heart rate variability (HRV) analysis, average beat morphology analysis, and atrial activity analysis focused on the P-wave amplitude in the average beat and f-waves amplitude in TQ intervals [ 28 ];
- Decision tree classifiers are input with 30 multi-level features, including measures of AF, morphology, RR intervals and similarity between beats [ 29 ]; morphological coefficients and HRV features calculated by ECG waveform fitting with a piecewise linear spline [ 30 ]; 400 hand-crafted features, reflecting the complex physiology of cardiac arrhythmias visible in single-channel ECG [ 31 ]; and 74 features of the R-peak amplitude, RR-interval statistics, PQRST statistics, ECG signal irregularity, entropy, noise content and four additional sparse coding features [ 32 ];
- A multi-layer binary classification architecture is input with subsets of 77, 66 and 19 features selected from 188 dimensional feature pool containing time, frequency, morphological and statistical domain ECG features [ 33 ];
- A multi-stage classifier, combining SVM, decision tree and threshold-based rules is quantifying both atrial and ventricular activity, estimated by local features (beat classification) and global features (rhythm, signal quality, similarity) [ 34 ].
- Advanced multi-stage classifiers, combining decision trees and neural networks (NNs) include: a tree gradient boosting model and a recurrent long, short-term memory (LSTM) network as a global classifier that uses 42 summary ECG features of the full record and a sequence classifier that works on a beat-by-beat basis using individual features of each cardiac cycle [ 35 ]; a bagged tree ensemble with 43 input features based on QRS detection and PQRS morphology connected in parallel to a convolutional neural network (CNN) and a shallow NN for analysis of raw filtered ECG signals (8× envelograms, 1× band-pass) [ 36 ]; a nine-layer CNN for segmentation of P, QRS and T waves, inter-beat segments, noise and arrhythmic beats, additionally augmented by hand-crafted features, thus supplying a set of 181 features to eXtreme Gradient Boosting trees to classify the heart rhythm [ 37 ]; a densely connected ...
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