title: Circadian variation in the effects of aldosterone blockade on heart rate variability and QT dispersion in congestive heart failure.
abstract: OBJECTIVE
  The study was designed to comprehensively evaluate the circadian effects of aldosterone blockade on autonomic tone and QT dispersion in chronic heart failure (CHF).
  
  
  BACKGROUND
  Spironolactone therapy given in addition to angiotensin-converting enzyme inhibitors improved survival in CHF, but the mechanism of its benefit is uncertain. Experimental evidence suggests that aldosterone may have detrimental effects on the autonomic nervous system, especially during the morning hours.
  
  
  METHODS
  Twenty-eight patients with New York Heart Association class II to IV CHF received spironolactone 50 mg daily and placebo for four weeks each in a double-blind crossover fashion. After each treatment phase, a full circadian assessment was undertaken of spironolactone's autonomic effects. The assessment included monitoring heart rate, QT dispersion, continuous Holter recordings, heart rate variability (HRV) and norepinephrine kinetics.
  
  
  RESULTS
  Spironolactone significantly reduced all indices of QT dispersion. The reductions in QTcmax, QTd and QTcd were greatest at 6 AM. In addition, spironolactone had favorable autonomic effects, which were limited to the morning (6-10 AM), including heart rate reduction and an improvement in HRV.
  
  
  CONCLUSIONS
  Spironolactone reduced heart rate and improved HRV and QT dispersion in CHF. Its effects were particularly prominent during the morning hours.
authors.affiliation: University Department of Clinical Pharmacology and Therapeutics, Ninewells Hospital and Medical School, Dundee, United Kingdom.
authors.forename: K M
authors.initials: KM
authors.lastname: Yee
authors.forename: S D
authors.initials: SD
authors.lastname: Pringle
authors.forename: A D
authors.initials: AD
authors.lastname: Struthers
mesh_terms: D002940:Circadian Rhythm / Q000187:drug effects*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004562:Electrocardiography / Q000187:drug effects*; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D000451:Mineralocorticoid Receptor Antagonists / Q000494:pharmacology*; D009638:Norepinephrine / Q000493:pharmacokinetics; D013148:Spironolactone / Q000494:pharmacology*
chemical_list: D000451:Mineralocorticoid Receptor Antagonists; D013148:Spironolactone; D009638:Norepinephrine