Open AccessMeasure of the QT–RR Dynamic Coupling in Patients with the Long QT Syndrome
Author(s) -
Halamek Josef,
Couderc JeanPhilippe,
Jurak Pavel,
Vondra Vlastimil,
Zareba Wojciech,
Viscor Ivo,
Leinveber, M.Sc. Pavel
Publication year - 2012
Publication title -
annals of noninvasive electrocardiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.494
H-Index - 48
eISSN - 1542-474X
pISSN - 1082-720X
DOI - 10.1111/j.1542-474x.2012.00526.x
Subject(s) - qt interval , medicine , long qt syndrome , cardiology , electrocardiography , heart rate , short qt syndrome , ambulatory , anesthesia , blood pressure
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 (Gain F ), a slow gain (Gain L ), 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 Gain L (0.22 ± 0.06 vs. 0.18 ± 0.07, P < 0.0001) and Gain F (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.