title: QT variability and HRV interactions in ECG: quantification and reliability.
abstract: In this paper, a dynamic linear approach was used over QT and RR series measured by an automatic delineator, to explore the interactions between QT interval variability (QTV) and heart rate variability (HRV). A low-order linear autoregressive model allowed to separate and quantify the QTV fractions correlated and not correlated with HRV, estimating their power spectral density measures. Simulated series and artificial ECG signals were used to assess the performance of the methods, considering a respiratory-like electrical axis rotation effect and noise contamination with a signal-to-noise ratio (SNR) from 30 to 10 dB. The errors found in the estimation of the QTV fraction related to HRV showed a nonrelevant performance decrease from automatic delineation. The joint performance of delineation plus variability analysis achieved less than 20% error in over 75% of cases for records presenting SNRs higher than 15 dB and QT standard deviation higher than 10 ms. The methods were also applied to real ECG records from healthy subjects where it was found a relevant QTV fraction not correlated with HRV (over 40% in 19 out of 23 segments analyzed), indicating that an important part of QTV is not linearly driven by HRV and may contain complementary information.
authors.affiliation: Departamento de Matemática Aplicada, Faculdade de Ciências da Universidade do Porto and Centro de Matemática da UP, Rua Campo Alegre 687, 4169-007 Porto, Portugal. rbalmeid@fc.up.pt
authors.forename: Rute
authors.initials: R
authors.lastname: Almeida
authors.forename: Sónia
authors.initials: S
authors.lastname: Gouveia
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Rocha
authors.forename: Esther
authors.initials: E
authors.lastname: Pueyo
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Martínez
authors.forename: Pablo
authors.initials: P
authors.lastname: Laguna
mesh_terms: D000465:Algorithms; D001145:Arrhythmias, Cardiac / Q000175:diagnosis* / Q000503:physiopathology*; D003198:Computer Simulation; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis / Q000503:physiopathology; D008955:Models, Cardiovascular; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity