[Contribution of dynamic electrocardiography by Holter monitoring in the evaluation of congenital long QT syndrome patients].
OBJECTIVE
The purpose of this study was to evaluate the value of ambulatory electrocardiogram as a clinical tool to assess ventricular repolarization in patients with the congenital long QT syndrome.


METHODS
The study population comprised six patients and their data were compared to a control group of six patients matched in age and gender. The QT interval (ms), corrected by the heart rate, was measured in the first minute of each hour using two monitoring leads, with the mean of six consecutive complexes. The data obtained include the morphologic pattern of T wave, the mean 24-h QTc interval, relation between QT and cardiac cycle, QTc variability (assessed calculating hourly standard deviation of the interval and then obtaining the global 24-h mean), QTc dispersion (difference between the longest and shortest QTc interval).


RESULTS
In all patients abnormal patterns of T waves were detected with frequent episodes of T wave alternans. Mean 24-h QTc--patients: 598.2 +/- 73.8 ms; controls: 436.1 +/- 8.9 ms (p = 0.000). Linear correlation and regression between QT and heart rate-patients: r = 0.812; controls: r = 0.967 (p = 0.000). QTc variability-patients: 36.9 +/- 17.2 ms; controls: 14.7 +/- 2.1 ms (p = 0.01). QTc dispersion-patients: 168.3 +/- 70.2 ms; controls: 53.3 +/- 8.1 ms (p = 0.000).


CONCLUSIONS
The data showed increased hourly QTc variability. QTc dispersion and worse correlation between QT and heart rate. This data may reflect an abnormally augmented ventricular vulnerability.
Hospital Pró-Cardiaco/Pró-Ritmo/Ritmolab/Pró-Criança-Rio de Janeiro.
I G
IG
Maia
M L
ML
Fagundes
F
F
Cruz Filho
R C
RC
Barbosa
P A
PA
Alves
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate; D006801:Humans; D008133:Long QT Syndrome / Q000151:congenital* / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male
Contribuição de eletrocardiografia dinâmica pelo sistema Holter na avaliação de pacientes com a síndrome congênita do QT longo.