title: Classification of ictal and seizure-free HRV signals with focus on lateralization of epilepsy.
abstract: OBJECTIVE
  Epileptic onsets often affect the autonomic function of the body during a seizure, whether it is in ictal, interictal or post-ictal periods. The different effects of localization and lateralization of seizures on heart rate variability (HRV) emphasize the importance of autonomic function changes in epileptic patients. On the other hand, the detection of seizures is of primary interests in evaluating the epileptic patients. In the current paper, we analyzed the HRV signal to develop a reliable offline seizure-detection algorithm to focus on the effects of lateralization on HRV.
  
  
  METHODS
  We assessed the HRV during 5-min segments of continuous electrocardiogram (ECG) recording with a total number of 170 seizures occurred in 16 patients, composed of 86 left-sided and 84 right-sided focus seizures. Relatively high and low-frequency components of the HRV were computed using spectral analysis. Poincaré parameters of each heart rate time series considered as non-linear features. We fed these features to the Support Vector Machines (SVMs) to find a robust classification method to classify epileptic and non-epileptic signals. Leave One Out Cross-Validation (LOOCV) approach was used to demonstrate the consistency of the classification results.
  
  
  RESULTS
  Our obtained classification accuracy confirms that the proposed scheme has a potential in classifying HRV signals to epileptic and non-epileptic classes. The accuracy rates for right-sided and left-sided focus seizures were obtained as 86.74% and 79.41%, respectively.
  
  
  CONCLUSIONS
  The main finding of our study is that the patients with right-sided focus epilepsy showed more reduction in parasympathetic activity and more increase in sympathetic activity. It can be a marker of impaired vagal activity associated with increased cardiovascular risk and arrhythmias. Our results suggest that lateralization of the seizure onset zone could exert different influences on heart rate changes. A right-sided seizure would cause an ictal tachycardia whereas a left-sided seizure would result in an ictal bradycardia.
authors.affiliation: Department of Electrical Engineering, Islamic Azad University, Garmsar, Iran.
authors.forename: Soroor
authors.initials: S
authors.lastname: Behbahani
authors.affiliation: Department of Biomedical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Nader Jafarnia
authors.initials: NJ
authors.lastname: Dabanloo
authors.affiliation: Department of Biomedical Engineering, Shahed University, Tehran, Iran.
authors.forename: Ali Motie
authors.initials: AM
authors.lastname: Nasrabadi
authors.affiliation: Center for Informatics and Systems (CISUC), University of Coimbra, Coimbra, Portugal.
authors.forename: Antonio
authors.initials: A
authors.lastname: Dourado
mesh_terms: D000293:Adolescent; D000328:Adult; D001342:Autonomic Nervous System Diseases / Q000209:etiology / Q000503:physiopathology*; D004562:Electrocardiography; D004827:Epilepsy / Q000145:classification* / Q000150:complications / Q000503:physiopathology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013610:Tachycardia / Q000209:etiology / Q000503:physiopathology*; D055815:Young Adult
keywords: Epileptic seizures; HRV; classification; lateralization; support vector machines