Halamek J, Couderc JP, Jurak P, Vondra V, Zareba W, Viscor I, Leinveber P. Measure of the QT-RR dynamic coupling in patients with the long QT syndrome.
Ann Noninvasive Electrocardiol 2012;
17:323-30. [PMID:
23094878 DOI:
10.1111/j.1542-474x.2012.00526.x]
[Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
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.
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