title: Can QT/RR relationship differentiate between low- and high-risk patients with hypertrophic cardiomyopathy?
abstract: BACKGROUND
  Abnormal dynamicity of repolarization is considered to be a marker of myocardial vulnerability contributing to increased risk of arrhythmic events and sudden death. However, little is known about QT dynamics in hypertrophic cardiomyopathy (HCM). In this study, we aimed to evaluate ventricular repolarization by QT dynamicity in patients with HCM, focusing on its value to define if it is able to differentiate among low- and high-risk HCM patients.
  
  
  METHODS
  The linear regression slopes of the QT interval, measured to the apex and to the end of the T wave plotted against RR intervals (QTapex/RR and QTend/RR slopes, respectively) were calculated from 24-hour Holter recordings using a standard algorithm in 36 HCM patients and 64 control subjects.
  
  
  RESULTS
  QTapex/RR and QTend/RR slopes were significantly steeper in the HCM patients in contrary to healthy control subjects (QTapex/RR = 0.22 + 0.08 vs 0.20 + 0.05, P = 0.0367; QTend/RR = 0.25 + 0.10 vs 0.20 + 0.06, P = 0.023). Moreover, the slopes of QTend/RR and QTapex/RR of high-risk patients were significantly steeper than those of control subjects while no significant differences were found among low-risk HCM patients and control subjects and only QTe/RR of high-risk patients was significantly different between low- and high-risk HCM patients.
  
  
  CONCLUSIONS
  Our study results suggest that QT dynamicity is impaired in patients with HCM and may help to differentiate among low- and high-risk patients. Further studies are needed to elucidate the prognostic significance and clinical implications of impaired ventricular repolarization in patients with HCM.
authors: Cardiac Electrophysiology Laboratory, Favaloro University, Buenos Aires, Argentina.
authors: Ricardo A
authors: RA
authors: Quinteiro
authors: Cardiac Electrophysiology Laboratory, Favaloro University, Buenos Aires, Argentina.
authors: Marcelo O
authors: MO
authors: Biagetti
authors: the Cardiology Division of the University Hospital, Favaloro University, Buenos Aires, Argentina.
authors: Adrian
authors: A
authors: Fernandez
authors: Cardiac Electrophysiology Laboratory, Favaloro University, Buenos Aires, Argentina.
authors: Francisco R
authors: FR
authors: Borzone
authors: the Cardiology Division of the University Hospital, Favaloro University, Buenos Aires, Argentina.
authors: Agustina
authors: A
authors: Gargano
authors: the Cardiology Division of the University Hospital, Favaloro University, Buenos Aires, Argentina.
authors: Horacio J
authors: HJ
authors: Casabe
mesh_terms: D000328:Adult; D001145:Arrhythmias, Cardiac / Q000150:complications* / Q000503:physiopathology*; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications* / Q000503:physiopathology*; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012306:Risk
keywords: noninvasive techniques-Holter/event recorders; noninvasive techniques-QT dispersion
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