Autonomic control of heart rate and QT interval variability influences arrhythmic risk in long QT syndrome type 1

Alberto Porta, Giulia Girardengo, Vlasta Bari, Alfred L. George, Paul A. Brink, Althea Goosen, Lia Crotti, Peter J. Schwartz

Research output: Contribution to journalArticle

Abstract

Background A puzzling feature of the long QT syndrome (LQTS) is that family members carrying the same mutation often have divergent symptoms and clinical outcomes. Objectives This study tested the hypothesis that vagal and sympathetic control, as assessed by spectral analysis of spontaneous beat-to-beat variability of RR and QT intervals from standard 24-h electrocardiogram Holter recordings, could modulate the severity of LQTS type 1 (LQT1) in 46 members of a South-African LQT1 founder population carrying the clinically severe KCNQ1 A341V mutation. Methods Nonmutation carriers (NMCs) (n = 14) were compared with mutation carriers (MCs) (n = 32), 22 with and 10 without major symptoms. We assessed the effect of circadian rhythm and beta-blocker therapy over traditional time and frequency domain RR and QT variability indexes. Results The asymptomatic MCs differed significantly from the symptomatic MCs and from NMCs in less vagal control of heart rate and more reactive sympathetic modulation of the QT interval, particularly during daytime when arrhythmia risk for patients with LQT1 is greatest. Conclusions The present data identified an additional factor contributing to the differential arrhythmic risk among patients with LQT1 carrying the same mutation. A healthy autonomic control confers a high risk, whereas patients with higher sympathetic control of the QT interval and reduced vagal control of heart rate are at lower risk. This differential "autonomic make-up," likely under genetic control, will allow refinement of risk stratification within families with LQTS, leading to more targeted management.

Original languageEnglish
Pages (from-to)367-374
Number of pages8
JournalJournal of the American College of Cardiology
Volume65
Issue number4
DOIs
Publication statusPublished - Feb 3 2015

Keywords

  • autonomic nervous system
  • beta-blocker therapy
  • cardiovascular control
  • heart rate variability
  • QT variability

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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