title: Prompt and accurate diagnosis of ventricular arrhythmias with a novel index based on phase space reconstruction of ECG.
abstract: OBJECTIVE
  To develop a statistical index based on the phase space reconstruction (PSR) of the electrocardiogram (ECG) for the accurate and timely diagnosis of ventricular tachycardia (VT) and ventricular fibrillation (VF).
  
  
  METHODS
  Thirty-two ECGs with sinus rhythm (SR) and 32 ECGs with VT/VF were analyzed using the PSR technique. Firstly, the method of time delay embedding were employed with the insertion of delay "τ" in the original time-series X(t), which produces the Y(t)=X(t-τ). Afterwards, a PSR diagram was reconstructed by plotting Y(t) against X(t). The method of box counting was applied to analyze the behavior of the PSR trajectories. Measures as mean (μ), standard deviation (σ) and coefficient of variation (CV=σ/μ), kurtosis (β) for the box counting of PSR diagrams were reported.
  
  
  RESULTS
  During SR, CV was always <0.05, while with the onset of arrhythmia CV increased >0.05. A similar pattern was observed with β, where <6 was considered as the cut-off point between SR and VT/VF. Therefore, the upper threshold for SR was considered CVth=0.05 and βth<6. For optimisation of the accuracy, a new index (J) was proposed: J=wCVCVth+1-wββth. During SR the upper limit of J was the value of 1. Furthermore CV, β and J crossed the cut-off point timely before the onset of arrhythmia (average time: 4min 31s; SD: 2min 30s); allowing sufficient time for preventive therapy.
  
  
  CONCLUSIONS
  The J index improved ECG utility for arrhythmia monitoring and detection utility, allowing the prompt and accurate diagnosis of ventricular arrhythmias.
authors.affiliation: University Hospital Southampton NHS Foundation Trust, UK; Department of Cardiology, Castle Hill Hospital, Hull York Medical School (at University of Hull), Kingston Upon Hull, UK.
authors.forename: George
authors.initials: G
authors.lastname: Koulaouzidis
authors.affiliation: School of Electronics and Computer Science, University of Southampton, UK.
authors.forename: Saptarshi
authors.initials: S
authors.lastname: Das
authors.affiliation: School of Electronics and Computer Science, University of Southampton, UK.
authors.forename: Grazia
authors.initials: G
authors.lastname: Cappiello
authors.affiliation: School of Electronics and Computer Science, University of Southampton, UK.
authors.forename: Evangelos B
authors.initials: EB
authors.lastname: Mazomenos
authors.affiliation: School of Electronics and Computer Science, University of Southampton, UK.
authors.forename: Koushik
authors.initials: K
authors.lastname: Maharatna
authors.affiliation: Department of Cardiovascular Sciences, Sapienza University of Rome, Italy.
authors.forename: Paolo E
authors.initials: PE
authors.lastname: Puddu
authors.affiliation: University Hospital Southampton NHS Foundation Trust, UK.
authors.forename: John M
authors.initials: JM
authors.lastname: Morgan
mesh_terms: D000465:Algorithms; D042241:Early Diagnosis; D004562:Electrocardiography / Q000379:methods*; D006801:Humans; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology
keywords: Index; Phase space reconstruction of ECG; Timely diagnosis; Ventricular arrhythmias