title: Abnormal ventricular repolarization in hypertensive patients: role of sympatho-vagal imbalance and left ventricular hypertrophy.
abstract: BACKGROUND
  An increased risk for life-threatening arrhythmias and sudden death has been observed in hypertensive patients, associated with either left ventricular hypertrophy (LVH) or prolonged QT interval. To investigate the influence of autonomic imbalance and LVH on QT interval in hypertensive patients, we compared two different models of LVH: hypertension and endurance physical training.
  
  
  METHODS
  Forty-seven untreated subjects affected by essential hypertension and 35 endurance runners, with a similar degree of LVH, were enrolled into the study. All subjects underwent 24-h ambulatory ECG recording and morning blood sampling for catecholamines. Heart rate variability was evaluated by spectral analysis and a computerized algorithm was used to measure the QT interval; QTc was then computed by the Bazett's formula. Left ventricular mass index (LVMI) was assessed by echocardiogram.
  
  
  RESULTS
  No difference in LVMI was found between hypertensive patients and athletes. Athletes showed lower heart rate (64 +/- 1 vs. 75 +/- 1 bpm, p<0.001, mean +/- S.E.M.) and shorter QTc (401 +/- 3 vs. 434 +/- 4 ms, p<0.001) than hypertensive patients throughout the 24-h period. Athletes showed a higher vagal drive compared to hypertensive patients as suggested by bradycardia and higher values of vagal indices, which negatively correlated with QTc. Plasma norepinephrine was significantly lower in athletes than in hypertensive patients (p<0.05) and positively correlated with QTc.
  
  
  CONCLUSIONS
  Despite similar degrees of LVH, hypertensive patients show QTc lengthening, as compared to athletes. Heart rate variability and plasma norepinephrine levels suggest sympathetic predominance in hypertensive patients, which could contribute to abnormal ventricular repolarization, thus identifying patients with an increased arrhythmic risk.
authors.affiliation: Institute of Clinical Physiology, National Research Council, Via Moruzzi 1, 56124 Pisa, Italy. passino@ifc.cnr.it
authors.forename: Claudio
authors.initials: C
authors.lastname: Passino
authors.forename: Ferdinando
authors.initials: F
authors.lastname: Franzoni
authors.forename: Alessandra
authors.initials: A
authors.lastname: Gabutti
authors.forename: Roberta
authors.initials: R
authors.lastname: Poletti
authors.forename: Fabio
authors.initials: F
authors.lastname: Galetta
authors.forename: Michele
authors.initials: M
authors.lastname: Emdin
mesh_terms: D001341:Autonomic Nervous System / Q000503:physiopathology; D002940:Circadian Rhythm; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000503:physiopathology*; D017379:Hypertrophy, Left Ventricular / Q000150:complications / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged