title: Ventricular repolarization is prolonged in nondipper hypertensive patients: role of left ventricular hypertrophy and autonomic dysfunction.
abstract: OBJECTIVE
  The aim of this study was to investigate the influence of circadian behavior of blood pressure, left ventricular hypertrophy, and autonomic function on QTc interval duration in untreated hypertensive patients.
  
  
  METHODS
  Hypertensive patients underwent simultaneous blood pressure and ECG 24-h ambulatory monitoring. Patients were classified into two groups on the basis of a lack of nocturnal fall in blood pressure, as dippers and nondippers. A group of normotensive healthy subjects was studied as controls.
  
  
  METHODS
  QT and QTc intervals were automatically computed and spectral analysis was applied to RR interval time series from the same electrocardiogram (ECG) recordings. Left ventricular mass index (LVMI) was computed by echocardiogram.
  
  
  RESULTS
  No difference among the three groups was found concerning mean values and circadian pattern of heart rate; by contrast, QTc was significantly longer in nondippers compared to dippers or to normotensive subjects, particularly at night-time, whereas all groups exhibited similar circadian variations in heart rate. Compared to dippers, nondippers showed significantly higher LVMI, which positively correlated with QTc, and parasympathetic withdrawal, which negatively correlated with QTc.
  
  
  CONCLUSIONS
  Nondippers show a prolonged ventricular repolarization throughout the 24-h period, absent either in dippers or normotensives. The association of left ventricular hypertrophy and vagal deactivation may lead to prolongation of QTc, potentially facilitating ventricular arrhythmias in nondipper hypertensive patients.
authors.affiliation: Institute of Clinical Physiology, National Research Council, Pisa, Italy. passino@ifc.cnr.it
authors.forename: Claudio
authors.initials: C
authors.lastname: Passino
authors.forename: Armando
authors.initials: A
authors.lastname: Magagna
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Conforti
authors.forename: Simona
authors.initials: S
authors.lastname: Buralli
authors.forename: Michaela
authors.initials: M
authors.lastname: Kozáková
authors.forename: Carlo
authors.initials: C
authors.lastname: Palombo
authors.forename: Michele
authors.initials: M
authors.lastname: Emdin
mesh_terms: D000328:Adult; D001342:Autonomic Nervous System Diseases / Q000150:complications / Q000503:physiopathology; D001794:Blood Pressure; D016022:Case-Control Studies; D002940:Circadian Rhythm; D004452:Echocardiography; D015716:Electrocardiography, Ambulatory; D004594:Electrophysiology; D005260:Female; D006339:Heart Rate; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000503:physiopathology*; D017379:Hypertrophy, Left Ventricular / Q000209:etiology; D008297:Male; D008875:Middle Aged; D013564:Sympathetic Nervous System / Q000503:physiopathology; D013997:Time Factors; D014630:Vagus Nerve / Q000503:physiopathology; D016276:Ventricular Function