Low-K+ dependent QT prolongation and risk for ventricular arrhythmia in anorexia nervosa

Mario Facchini, Luca Sala, Gabriella Malfatto, Renato Bragato, Gabriella Redaelli, Cecilia Invitti

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Abstract

Background: QT prolongation and ventricular arrhythmia have been proposed as the mechanism for sudden death in anorexia nervosa. The prevalence and the cause of QT prolongation remain controversial. Objectives: 1) to evaluate ventricular repolarization in patients with anorexia; 2) to evaluate factors that may influence repolarization, with focus on electrolyte plasma levels and heart rate. Methods: 29 patients with anorexia, age 22 ± 5 years, BMI 13.8 ± 1.5 were compared to 14 control female subjects, age 23 ± 2 years, BMI 20.7 ± 1.1. QT interval and QT dispersion were measured. Whenever a low potassium (<3.5 mEq/l) was found, ECG was repeated after normalization of serum levels. Heart rate and its variability in the frequency domain (LF/HF ratio) were evaluated. Results: Three patients (10.3%) showed severe hypokalemia (K+ levels <2.0 mEq/l). In 2 patients, QT was severely prolonged (QTc 600 and 670 msec) and in one case associated with ventricular arrhythmia. QTc after K+ plasma levels normalization was 392 ± 25 in anorexia vs. 407 ± 19 msec in controls, p = 0.08. Heart rate was 55 ± 11 in anorexia vs. 66 ± 8 beats per minute (BPM) in controls, p = 0.002. The LF/HF ratio was 1.79 ± 1.35 in anorexia and 3.66 ± 2.64 in controls, p = 0.006. Conclusions: QT interval is usually normal in patients with anorexia. QT prolongation and ventricular arrhythmia may develop in the setting of severe hypokalemia, exposing patients to high risk of sudden cardiac event. Resting heart rate is lower in anorexia than in controls with the spectral indices of sympatho-vagal balance indicating a prevalence of vagal activity.

Original languageEnglish
Pages (from-to)170-176
Number of pages7
JournalInternational Journal of Cardiology
Volume106
Issue number2
DOIs
Publication statusPublished - Jan 13 2006

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Keywords

  • Anorexia nervosa
  • Heart rate variability
  • Hypokalemia
  • QT interval
  • Ventricular arrhythmia

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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