Vagal reflexes following an exercise stress test: A simple clinical tool for gene-specific risk stratification in the long QT syndrome

Lia Crotti, Carla Spazzolini, Alessandra P. Porretta*, Federica Dagradi, Erika Taravelli, Barbara Petracci, Alessandro Vicentini, Matteo Pedrazzini, Maria Teresa La Rovere, Emilio Vanoli, Althea Goosen, Marshall Heradien, Alfred L. George, Paul A. Brink, Peter J. Schwartz

*Corresponding author for this work

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

Objectives: The study assessed whether heart rate (HR) reduction following an exercise stress test (ExStrT), an easily quantifiable marker of vagal reflexes, might identify high- and low-risk long QT syndrome (LQTS) type 1 (LQT1) patients. Background: Identification of LQTS patients more likely to be symptomatic remains elusive. We have previously shown that depressed baroreflex sensitivity, an established marker of reduced vagal reflexes, predicts low probability of symptoms among LQT1. Methods: We studied 169 LQTS genotype-positive patients < 50 years of age who performed an ExStrT with the same protocol, on and off β-blockers including 47 South African LQT1 patients all harboring the KCNQ1-A341V mutation and 122 Italian LQTS patients with impaired (IKs-, 66 LQT1) or normal (IKs+, 50 LQT2 and 6 LQT3) IKs current. Results: Despite similar maximal HR and workload, by the first minute after cessation of exercise the symptomatic patients in both IKs- groups had a greater HR reduction compared with the asymptomatic (19 ± 7 beats/min vs. 13 ± 5 beats/min and 27 ± 10 beats/min vs. 20 ± 8 beats/min, both p = 0.009). By contrast, there was no difference between the IKs+ symptomatic and asymptomatic patients (23 ± 9 beats/min vs. 26 ± 9 beats/min, p = 0.47). LQT1 patients in the upper tertile for HR reduction had a higher risk of being symptomatic (odds ratio: 3.28, 95% confidence interval: 1.3 to 8.3, p = 0.012). Conclusions: HR reduction following exercise identifies LQT1 patients at high or low arrhythmic risk, independently of β-blocker therapy, and contributes to risk stratification. Intense exercise training, which potentiates vagal reflexes, should probably be avoided by LQT1 patients.

Original languageEnglish (US)
Pages (from-to)2515-2524
Number of pages10
JournalJournal of the American College of Cardiology
Volume60
Issue number24
DOIs
StatePublished - Dec 18 2012

Keywords

  • autonomic nervous system
  • exercise testing
  • genetics
  • long QT syndrome
  • sudden death

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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    Crotti, L., Spazzolini, C., Porretta, A. P., Dagradi, F., Taravelli, E., Petracci, B., Vicentini, A., Pedrazzini, M., La Rovere, M. T., Vanoli, E., Goosen, A., Heradien, M., George, A. L., Brink, P. A., & Schwartz, P. J. (2012). Vagal reflexes following an exercise stress test: A simple clinical tool for gene-specific risk stratification in the long QT syndrome. Journal of the American College of Cardiology, 60(24), 2515-2524. https://doi.org/10.1016/j.jacc.2012.08.1009