title: Shortening baroreflex delay in hypertrophic cardiomyopathy patients -- an unknown effect of β-blockers.
abstract: OBJECTIVE
  Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy and impaired diastolic and systolic function. Abnormal sympathetic-parasympathetic balance is a potential stimulus for left ventricular hypertrophy in HCM patients. β-Blockers are routinely used in HCM for their strong negative inotropic effect; however, these drugs also influence the sympathetic-parasympathetic balance. This study aimed to determine the autonomic control of the cardiovascular system and the autonomic effects of β-blockers in HCM patients treated or untreated with β-blockers.
  
  
  METHODS
  Among 51 HCM outpatients (18-70 years old; 29 men) there were 19 individuals with no medication and 32 subjects treated with a β-blocker. Fourteen age- and gender-matched (23-70 years old; nine men) healthy volunteers were enrolled in the control group. Continuous, non-invasive finger blood pressure was recorded during supine rest for 30 min. Autonomic regulation of the cardiovascular system was measured by heart rate variability and spontaneous baroreflex function (cross-correlation sequence method).
  
  
  RESULTS
  The mean pulse interval, time domain and spectral measures of heart rate variability and baroreflex sensitivity were comparable between HCM patients, treated or not with β-blockers, and the control group. However, the delay of the baroreflex was significantly longer in HCM patients who were not treated with β-blockers [2.0 (1.6-2.3) s] in comparison with HCM patients receiving β-blockers [1.4 (1.1-1.8) s; P = 0.0072] or control subjects [1.2 (0.8-1.8) s; P = 0.0025]. This delay did not differ between HCM patients treated with β-blockers and the control group.
  
  
  CONCLUSIONS
  Hypertrophic cardiomyopathy not treated with β-blockers is accompanied by prolonged baroreflex delay. The use of β-blockers normalizes this delay.
authors.affiliation: Department of Cardiology - First Department, Poznan University of Medical Sciences, Poznan, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Katarzynska-Szymanska
authors.forename: Romuald
authors.initials: R
authors.lastname: Ochotny
authors.forename: Zofia
authors.initials: Z
authors.lastname: Oko-Sarnowska
authors.forename: Hanna
authors.initials: H
authors.lastname: Wachowiak-Baszynska
authors.forename: Tomasz
authors.initials: T
authors.lastname: Krauze
authors.forename: Jaroslaw
authors.initials: J
authors.lastname: Piskorski
authors.forename: Adrian
authors.initials: A
authors.lastname: Gwizdala
authors.forename: Przemyslaw
authors.initials: P
authors.lastname: Mitkowski
authors.forename: Przemyslaw
authors.initials: P
authors.lastname: Guzik
mesh_terms: D000293:Adolescent; D058671:Adrenergic beta-1 Receptor Antagonists / Q000627:therapeutic use*; D000328:Adult; D000368:Aged; D017704:Baroreflex / Q000187:drug effects*; D017298:Bisoprolol / Q000627:therapeutic use; D002312:Cardiomyopathy, Hypertrophic / Q000188:drug therapy*; D016022:Case-Control Studies; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D008790:Metoprolol / Q000627:therapeutic use; D008875:Middle Aged; D013997:Time Factors; D055815:Young Adult
chemical_list: D058671:Adrenergic beta-1 Receptor Antagonists; D008790:Metoprolol; D017298:Bisoprolol