Abnormal nocturnal heart rate variability and QT dynamics in patients with Brugada syndrome.
BACKGROUND
In Brugada syndrome (BSY), most of the ventricular arrhythmic events are nocturnal, suggesting an influence of the autonomic nervous system.


METHODS
In 46 patients (mean age = 41 +/- 14 years, 43 men) with electrocardiograms (ECG) consistent with BSY and structurally normal hearts, we measured heart rate variability (HRV) and QT dynamics (QT/RR slopes) on 24-hour ambulatory ECG. Type 1 BSY-ECG was spontaneous in 23 (50%) and induced in 23 patients.


RESULTS
History of syncope was present in 23 patients (50%). Programmed ventricular stimulation induced ventricular tachyarrhythmias (VTA) in 13 patients (28%). A single patient developed ventricular tachycardia during a mean follow-up of 34 months. Compared to a control group matched for age and sex, HRV was decreased over 24 hours and during nighttime in patients with BSY (SDNN 122 +/- 44 vs 93 +/- 36 ms, P = 0.0008 and SDANN 88 +/- 39 vs 54 +/- 24 ms, P < 0.0001). QTend /RR slopes were decreased over 24 hours in patients with BSY (0.159 +/- 0.05 vs 0.127 +/- 0.05, P = 0.003) and particularly at night (0.123 +/- 0.04 vs 0.089 +/- 0.04, P = 0.0001). QTend /RR slopes were significantly decreased during nighttime in patients with spontaneous versus provoked BSY-ECG patterns. By contrast, HRV and QT/RR slopes were similar in symptomatic and asymptomatic patients, whether VTA were induced or not.


CONCLUSIONS
Patients with a BSY-ECG pattern had lower HRV and QT/RR slopes than control subjects during nighttime. High-risk patients with spontaneous BSY-ECG patterns had the lowest nocturnal QTend/RR slopes. These unique repolarization dynamics might be related to the frequent nocturnal occurrence of VTA in BSY.
Pierre
Bertrand
B
Services de Cardiologie B et Laboratoire D'electrophysiologie Cardiaque, Centre Hospitalier Universitaire Trousseau, 37044 Tours, France.
Babuty
Dominique
D
Poret
Philippe
P
Giraudeau
Cedric
C
Marie
Olivier
O
Cosnay
Pierre
P
Fauchier
Laurent
L
D000328:Adult; D053840:Brugada Syndrome / Q000503:physiopathology*; D016022:Case-Control Studies; D002940:Circadian Rhythm; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000503:physiopathology*