Non-invasive Wedensky modulation within the QRS complex

  • K. Hnatkova
  • S. J. Ryan
  • J. Bathen
  • H. H. Hoium
  • M. Malik


To investigate non-invasively induced Wedensky modulation, 2 ms pulses of 5, 20 and 40 mA were delivered between precordial and subscapular patches synchronously with the QRS complex. Wavelet vector magnitude was obtained for averaged modulated and non-modulated complexes. The surface area of a 3D-envelope of their difference (WSR) was compared in 59 patients with an uncomplicated follow-up after myocardial infarction (MI) (42 men, 64.3±9.1 years), in 30 patients with ischaemic heart disease and a history of ventricular tachycardia/fibrillation (VT/VF) (29 men, 63.1±9.8 years), and in 53 healthy subjects (control) (22 men, 56.6±10.1 years). Reproducibility of the assessment was tested by computing relative errors in a sub-population of 30 VT/VF patients and 47 controls. Wedensky modulation parameters differed significantly between control, MI and VT/VF subjects. In 10 ms post-modulation windows, the following WSR values were obtained: controls: 1184±496 (5 mA), 1553±838 (20 mA) and 2092±1488 (40 mA); VT/VF: 861±412 (5 mA), 1134±636 (20 mA) and 1320±1036 (40 mA); MI: 1305±885 (5 mA) and 1779±1169 (20 mA). With all modulating energies used, the VT/VF patients differed significantly from both the controls and MI patients; control patients against VT/VF patients: p<0.004 (5 mA), p<0.01 (20 mA) and p<0.001 (40 mA); VT/VF patients against MI patients: p<0.02 (5 mA), p<0.01 (20 mA); control patients against MI patients: all p=NS. The reproducibility assessment showed an acceptable stability of Wedensky modulation parameters. This study demonstrated that wavelet decomposition detects non-invasive Wedensky modulation within the QRS complex, and VT/VF patients are less sensitive to Wedensky modulation than control and MI patients.


Wedensky modulation Ventricular tachycardia Myocardial infarction Signal averaged electrocardiogram Wavelet decomposition 


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Copyright information

© IFMBE 2002

Authors and Affiliations

  • K. Hnatkova
    • 1
  • S. J. Ryan
    • 2
  • J. Bathen
    • 3
  • H. H. Hoium
    • 2
  • M. Malik
    • 1
  1. 1.Department of Cardiological SciencesSt George's Hospital Medical SchoolLondonUK
  2. 2.Harbinger Medical Inc.MinneapolisUSA
  3. 3.Regional HospitalTrondheimNorway

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