title: Time-frequency analysis of the ECG in the diagnosis of vasovagal syndrome in older people.
abstract: The Smoothed Pseudo Wigner-Ville Distribution (SPWVD) is used for the time-frequency analysis of variations in RR interval. A novel technique to determine the smoothing window lengths is implemented, and a new heart rate variability (HRV) metric is developed, instantaneous center frequency variability (ICFV), which uses the time-frequency map generated by the SPWVD. The technique is then applied to 50 patients with unexplained falls and age > 60, undergoing head-upright tilt table testing (HUT). Eighteen of the patients were diagnosed with vasovagal syndrome. Attempts at syncope prediction using the new metric is an improvement on traditional techniques: an ICFV less than 0.07 Hz from 90 s to 180 s after tilt is predictive of a negative test (negative predictive value: 0.77). The comorbidity and autonomic degeneration present in elderly patients are thought to be responsible for lowering the negative predictive value.
authors.affiliation: Dept. of Eng. Sci., Oxford Univ., UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Ebden
authors.forename: L
authors.initials: L
authors.lastname: Tarassenko
authors.forename: S J
authors.initials: SJ
authors.lastname: Payne
authors.forename: A
authors.initials: A
authors.lastname: Darowski
authors.forename: J D
authors.initials: JD
authors.lastname: Price