ORIGINAL ARTICLE

Measure of the QT–RR Dynamic Coupling in Patients with the Long QT Syndrome

  1. Josef Halamek Ph.D.1,
  2. Jean-Philippe Couderc Ph.D.2,
  3. Pavel Jurak Ph.D.1,
  4. Vlastimil Vondra Ph.D.1,
  5. Wojciech Zareba Ph.D., M.D.2,
  6. Ivo Viscor Ph.D.1,
  7. Pavel Leinveber, M.Sc.3

Article first published online: 13 AUG 2012

DOI: 10.1111/j.1542-474X.2012.00526.x

Issue

Annals of Noninvasive Electrocardiology

Annals of Noninvasive Electrocardiology

Volume 17, Issue 4, pages 323–330, October 2012

Additional Information

How to Cite

Halamek, J., Couderc, J.-P., Jurak, P., Vondra, V., Zareba, W., Viscor, I. and Leinveber, M.Sc., P. (2012), Measure of the QT–RR Dynamic Coupling in Patients with the Long QT Syndrome. Annals of Noninvasive Electrocardiology, 17: 323–330. doi: 10.1111/j.1542-474X.2012.00526.x

Author Information

  1. 1

    Institute of Scientific Instruments, AS CR, Brno, Czech Republic

  2. 2

    Center for Quantitative Electrocardiography and Cardiac Safety, Heart Research Follow-up Program, University of Rochester Medical Center, Rochester, NY, USA

  3. 3

    International Clinical Research Center, Center of Biomedical Engineering, St. Anne's University Hospital, Brno, Czech Republic

*Josef Halamek, Ph.D., Department of Magnetic Resonance and Bioinformatics, Institute of Scientific Instruments, AS CR, Brno, Kralovopolska 147, 612 64 Brno, Czech Republic. Fax: +420 541514402; E-mail: josef@isibrno.cz

  1. This work was partially supported by grant KONTAKT No. ME09050 of the Ministry of the Education of the Czech Republic, by European Regional Development Fund—Project FNUSA-ICRC No. CZ.1.05/1.1.00/02.0123, by the National Heart, Lung, and Blood Institute of the US Department of Healthy and Human Services grant U24HL096556 and by grant No. P102/12/2034 of the Grant Agency of the Czech Republic.

  2. Conflict of interest: None.

Publication History

  1. Issue published online: 25 OCT 2012
  2. Article first published online: 13 AUG 2012

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Keywords:

  • long QT syndrome;
  • dynamic QT–RR coupling;
  • Holter recording;
  • QT adaptation;
  • QT parameters

Background: The patients with the long QT syndrome type-1 (LQT-1) have an impaired adaptation of the QT interval to heart rate changes. Yet, the description of the dynamic QT–RR coupling in genotyped LQT-1 has never been thoroughly investigated.

Method: We propose a method to model the dynamic QT–RR coupling by defining a transfer function characterizing the relationship between a QT interval and its previous RR intervals measured from ambulatory Holter recordings. Three parameters are used to characterize the QT–RR coupling: a fast gain (GainF), a slow gain (GainL), and a time constant (τ). We investigated the values of these parameters across genders, and in genotyped LQT-1 patients with normal QTc interval duration (QTc  <  470 ms).

Results: The QT–RR dynamic profiles are significantly different between LQT-1 patients (97) and controls (154): LQT-1 have longer QTc interval (453  ± 35 vs. 384  ± 26 ms, P  <  0.0001), and an increased dependency of the QT interval to previous RR changes revealed by a larger GainL (0.22  ± 0.06 vs. 0.18  ± 0.07, P  <  0.0001) and GainF (0.05  ± 0.02 vs. 0.03  ± 0.01, P  <  0.0001). Importantly, LQT-1 patients have a faster QT dynamic response to previous RR changes described by τ: 122  ± 44 vs. 172  ± 92 beats (P  <  0.0001). This faster QT dynamic response of the QT–RR dynamic coupling remained in LQT-1 patients with QTc in a normal range (<430 ms).

Conclusions: The measurement of QT–RR dynamic coupling could be used in patients suspected to carry a concealed form of the LQT-1 syndrome, or to provide insights into the types of arrhythmogenic triggers a patient may be prone to.

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