Abstract
The goal of this research was to classify cardiac excitation patterns during atrial fibrillation (AFib). For this purpose, virtual models of intracardiac mapping catheters were moved across in-silico cardiac tissue to extract local activation times (LATs) of each catheter electrode from simulated cardiac action potential (AP) signals. The resulting LAT patterns consisting of the LATs of all electrodes resemble patterns measured in clinical cases. The LATs represent the input information for features that were used to separate four different excitation patterns during AFib. Those four excitation patterns were plane wave, ectopic focus (spherical wave), rotor (spiral wave) and block. A feature selection algorithm was used to investigate the features concerning their power to classify the different simulated excitation patterns. The scores of the selected features were used to train and optimize a support vector machine (SVM). The optimized and cross-validated SVM was then used to classify the simulated cardiac excitation patterns. The achieved overall classification accuracy of this SVM model was 98.4 %.
1 Introduction
Atrial fibrillation (AFib) is the most common type of cardiac arrhythmia worldwide. Despite many years of research and the clinical relevance, its electrophysiological mechanisms of initiation and maintenance are still not well enough understood. Different theories favor multiple wavelets, ectopic foci and rotor sources as potential drivers for the maintenance of AFib. During intracardiac electrophysiological studies, clinicians try to find those drivers of AFib using different types of intracardiac mapping catheters. The corresponding excitation patterns can be simulated based on in-silico models [1] and represent a known ground-truth for the presented study. Using this data, we assessed the possibility of classifying the underlying excitation patterns during diagnosis and benchmarked the resulting system.
2 Material and methods
2.1 Simulated data
Different theories for the initiation and maintenance of AFib and their potential driving sources were taken into account using four excitation scenarios: Plane wave, ectopic focus, rotor and block. The plane wave scenario represented the physiological case of excitation during normal sinus rhythm, where the excitation front in a certain distance to the sinus node was of such small curvature that it could be regarded as an approximate plane wave. The scenarios comprised virtual action potential (AP) signals for each voxel of a certain patch of tissue during one cycle of excitation and were simulated based on the CRN model of Courtemanche et al. [2]. The tissue patches comprised 400 × 400 voxels with a spatial resolution of 0.2 mm. The rotor scenario was simulated based on the electrophysiological cell model of Nygren et al. and the tissue patch comprised 1000 × 1000 voxels with a spatial resolution of 0.1 mm [3]. Figure 1 shows for all four excitation scenarios one slice of those simulated patches colored by the transmembrane voltage (TMV) for a certain time step.

Color-coded TMV for one distinct time step of plane wave (A), ectopic focus (B), rotor (C) and block (D). The plane wave was started by a stimulus on the left side of the patch, the spherical wave by a focal stimulus at (40 mm, 40 mm). The rotor was initiated by a cross-field stimulus and is centered at (49.5 mm, 42 mm). For the block scenario, the propagation of the plane wave was started by a stimulus on the lower left side of the patch and restricted by a line of block. This line of block is situated between coordinates (0 mm, 40 mm) and (60 mm, 40 mm).
Different types of virtual catheters were used to extract information from the simulated scenarios. In Figure 1(a), a virtual single loop catheter (20 electrodes marked as red dots, diameter 25 mm) is depicted which is used as an exemplary catheter model for all following statements and figures. AP signals were extracted at multiple catheter positions by moving the catheter model across the simulation patches in equidistant steps.
The morphology of the AP signals was similar for all electrode positions. Sufficient information to distinguish different excitation patterns is given by the distinct points in time when the excitation front passes each electrode, referred to as the local activation time (LAT) of each electrode. The LATs were annotated at the maximum positive gradient of the AP signals. In Figure 2(a) the AP signals (blue lines) extracted at the electrode positions of the virtual single loop catheter described above and the corresponding LATs (red dots) are depicted for a plane wave excitation pattern. A cosine-shaped pattern can be observed for the illustrated LATs. This cosine-shape is typical for all plane-like excitation patterns recorded with a single loop catheter [4], [5]. Thus, similar cosine-shaped LAT patterns were observable when the virtual catheter was placed distant from the focal or rotor source (referred to as their far field in this study) or distant from the block line. Other shapes of LAT patterns caused by different excitation patterns are shown in Figures2(b) to (d).

Exemplary LAT patterns for plane-like excitation patterns (A), focus (near field) (B), rotor (near field) (C) and catheter on block line (D). The annotated LATs are marked as red dots in the AP signals (blue lines). The center of the single loop catheter was situated at (20 mm, 20 mm) for (A), (36 mm, 36 mm) for (B), (47 mm, 47 mm) for (C) and (42 mm, 42 mm) for (D).
To further examine the separability of the plane-like excitation patterns, the four initial excitation pattern classes plane wave, ectopic focus, rotor and block were further split up into the seven subclasses plane wave (Plane), focus far field (FocusFar) and near field (FocusNear), rotor far field (RotorFar) and near field (RotorNear) as well as catheter distant from block (OffBlock) and on block (OnBlock). For each of those seven subclasses, 500 LAT patterns were recorded with varying location of the catheter with respect to the wave. To distinguish between them, suitable features had to be defined.
2.2 Features
Altogether, thirteen features were implemented. Those features can be subdivided into three groups:
Fitting features: The LAT pattern was fitted to a given function and the fitting error was used as a feature. When both the fitting function and the LAT pattern were cosine-shaped (i.e. the underlying excitation pattern was plane-like) the fitting error was smaller for this LAT pattern than for other, not cosine-shaped LAT patterns (see Figure 3).
Features based on a fast Fourier transform (FFT) of the LAT pattern: By calculating the FFT of an LAT pattern, knowledge about its similarity to a cosine-shaped pattern with the same number of sampling points was obtained: A cosine-shaped LAT pattern caused one dominant frequency peak in the spectral domain obtained by the FFT.
Features based on statistical parameters: statistical parameters were used to combine the LATs or LAT differences in different electrode configurations to obtain one coefficient used as a feature.

Cosine function fitting. (A) Plane LAT pattern. The cosine function is perfectly fitted to the LATs. (B) OnBlock LAT pattern. The phase shift of the LAT pattern causes a poorly fitted cosine function and thus a larger fitting error than for (A).
Two further features are the cycle length coverage (CLC) and a feature that measures the distribution of active periods in the LAT pattern (DistActive). The fitting features are based on [6], the other ones were introduced here. The CLC is a well-known measure in cardiology that was already used as a feature [4].
2.3 Feature selection
To obtain the optimal classification results, it was of vital importance to select suitable features. The favored feature selection approach comprised multiclass support vector machine (SVM) models and a canonical correlation analysis (CCA) of the features.
For the SVM models, a radial basis function (RBF) kernel was chosen as among other reasons only two parameters C and KernelScale had to be optimized. Here, C is a penalty parameter controlling the trade-off between the tolerated amount of misclassified training data points and the width of the margin around the classifier model’s separation border. KernelScale is a parameter introduced by MATLAB which has the value of KernelScale =
The feature selection approach is illustrated in Figure 4. In a first step, a separate multiclass SVM model was trained for each feature to assess the feature’s capability to separate the excitation pattern classes. Then all trained single-feature-SVMs were 10-fold cross-validated and the overall misclassification errors (MCE) of the cross-validated models were calculated as a measure for the capability to separate.

Different steps of feature selection algorithm. For details see text. CrV =cross-validation.
In a second step, CCA was applied to measure to which degree a feature could be represented by a linear combination of the other features. In this way, a measure for the redundancy of each feature was obtained. Every feature was tested against a linear combination of the features with a higher separability quality according to step 1. Thus, the second best feature was tested against the best one, the third best feature against a linear combination of the two best features and so on.
In a last step, all features with a predictive accuracy below a certain threshold or a certain similarity to a linear combination of all more relevant features were discarded. Both threshold values were found empirically.
2.4 Classification
To find the optimal parameter value pair of C and KernelScale for the training of the SVM model used to separate the excitation patterns, both parameters were varied in a certain range. For every value pair, a multiclass RBF SVM model was trained using the scores of the features selected in the previous step. The search range of the parameters was 10−3 to 104 for KernelScale and 10−3 to 107 for C. The trained multiclass SVM models were 10-fold cross-validated afterwards. The value pair yielding the highest overall classification accuracy among all cross-validated SVM models was defined to be the optimal one.
3 Results
The parameter optimization results are shown in Figure 5. The optimal parameter value pair was found at C = 104 and KernelScale = 10−1. When a multiclass RBF SVM model was trained with those parameter values and the scores of the selected features, the 10-fold cross-validated model achieved an overall classification accuracy of 98.4 %. More interesting than this single value are the classification results shown in Figure 6. Here, the class labels predicted by the SVM model are compared to the true class labels. The fields on the main diagonal of the confusion matrix state the percentage of correct classifications for all subclasses. Each field of the confusion matrix besides the main diagonal depicts the frequency of a certain misclassification scenario. The best separability was observable for the excitation patterns OnBlock, FocusNear and RotorNear with their characteristical LAT patterns. The plane-like excitation patterns were more often confused but still separable in nearly all cases.

Overall classification accuracy for cross-validated multiclass SVM models trained with scores of selected features for shown value pairs for parameters C and KernelScale.

Confusion matrix for 10-fold cross-validated multiclass RBF SVM model trained with scores of selected features and optimal parameter values C = 104 and KernelScale = 10−1. The values in the confusion matrix’ fields are given as percentages. An overall classification accuracy of 98.4 % is achieved.
4 Discussion
In this paper, a first proof of concept for a classification based interpretation of cardiac excitation patterns was given. However, a classification based on ideal simulated AP signals is expected to be simpler than a classification based on signals measured in clinical applications. Here, instead of TMVs only extracellular potentials Φe can be measured with intracardiac catheters. The annotation of LATs in the resulting unipolar or bipolar signals is less precise, as no steep, unique upstroke is given like for the AP signals and other criteria to annotate the LATs have to be applied. The loss in precision introduces a temporal uncertainty and thus jitter to the annotated LATs. The temporal jitter can be modeled as additive Gaussian noise on the LATs. Further studies with artificially corrupted simulated LAT patterns proved a decrease in classification accuracy.
Furthermore, as additional research showed for actual clinical data, the classification task becomes even more complicated in real-world clinical applications. Among others, catheter deformations and more complex LAT patterns are possible in clinical surroundings and would have to be considered to enable a classification of cardiac excitation patterns in everyday clinical practice.
Author’s Statement
Research funding: The author state no funding involved. Conflict of interest: Authors state no conflict of interest. Informed consent: Informed consent is not applicable. Ethical approval: The conducted research is not related to either human or animal use.
References
[1] Seemann G, Sachse FB, Karl M, Weiss DL, Heuveline V, Dössel O. Framework for modular, flexible and efficient solving the cardiac bidomain equation using PETSc. J Math Ind. 2010;15:363–9.10.1007/978-3-642-12110-4_55Search in Google Scholar
[2] Courtemanche M, Ramirez RJ, Nattel S. Ionic mechanisms underlying human atrial action potential properties: Insights from a mathematical model. Am J Physiol. 1998;275:H301–21.10.1152/ajpheart.1998.275.1.H301Search in Google Scholar PubMed
[3] Rottmann M, Keller MW, Oesterlein T, Seemann G, Dössel O. Comparison of different methods and catheter designs to estimate the rotor tip position – a simulation study. CinC. 2014:133–6.Search in Google Scholar
[4] Rottmann M, Unger L, Kaltenbacher W, Seemann G, Loewe A, Krueger MW, et al. Methods for analyzing signal characteristics of stable and unstable rotors in a realistic heart model. CinC. 2015:485–8.10.1109/CIC.2015.7410953Search in Google Scholar
[5] Weber FM, Schilling C, Seemann G, Luik A, Schmitt C, Lorenz C, et al. Wave-direction and conduction-velocity analysis from intracardiac electrograms – a single-shot technique. IEEE TBME. 2010;57:2394–401.10.1109/TBME.2010.2055056Search in Google Scholar PubMed
[6] Roney CH, Cantwell CD, Qureshi NA, Ali RL, Chang ETY, Lim PB, et al. An automated algorithm for determining conduction velocity, wavefront direction and origin of focal cardiac arrhythmias using a multipolar catheter. IEEE EMBC. 2014:1583–6.10.1109/EMBC.2014.6943906Search in Google Scholar PubMed
©2016 Christian Reich et al., licensee De Gruyter.
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.
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- Conversion of engineering stresses to Cauchy stresses in tensile and compression tests of thermoplastic polymers
- Numerical examinations of simplified spondylodesis models concerning energy absorption in magnetic resonance imaging
- Principle study on the signal connection at transabdominal fetal pulse oximetry
- Influence of Siluron® insertion on model drug distribution in the simulated vitreous body
- Evaluating different approaches to identify a three parameter gas exchange model
- Effects of fibrosis on the extracellular potential based on 3D reconstructions from histological sections of heart tissue
- From imaging to hemodynamics – how reconstruction kernels influence the blood flow predictions in intracranial aneurysms
- Flow optimised design of a novel point-of-care diagnostic device for the detection of disease specific biomarkers
- Improved FPGA controlled artificial vascular system for plethysmographic measurements
- Minimally spaced electrode positions for multi-functional chest sensors: ECG and respiratory signal estimation
- Automated detection of alveolar arches for nasoalveolar molding in cleft lip and palate treatment
- Control scheme selection in human-machine- interfaces by analysis of activity signals
- Event-based sampling for reducing communication load in realtime human motion analysis by wireless inertial sensor networks
- Automatic pairing of inertial sensors to lower limb segments – a plug-and-play approach
- Contactless respiratory monitoring system for magnetic resonance imaging applications using a laser range sensor
- Interactive monitoring system for visual respiratory biofeedback
- Development of a low-cost senor based aid for visually impaired people
- Patient assistive system for the shoulder joint
- A passive beating heart setup for interventional cardiology training