Dispersion of QT and QTc interval in healthy children, and effects of sinus arrhythmia on QT dispersion

Abstract

Objective-To determine the normal values of QT and QTc dispersion and the eVects of sinus arrhythmia on QT dispersion in healthy children. Patients and setting-The study was carried out in a university hospital on 372 local schoolchildren (200 male, 172 female), aged seven to 18 years. Methods-The QT and preceding RR intervals of at least one sinus beat were measured manually in a range of nine to 12 leads on standard 12 lead surface ECGs. The corrected QT interval was computed by the method of Bazett. Dispersion of QT and QTc were defined as (1) the diVerence between the maximum and minimum QT and QTc intervals occurring in any of the 12 leads (QTD and QTcD), (2) the standard deviation of the QT and QTc interval in the measurable leads (QT-SD and QTc-SD).Results-There was no significant diVerence in QT, QTc, and RR dispersion between girls and boys. Overall 53% of children had sinus arrhythmia. Although QTD and QT-SD were not aVected by sinus arrhythmia, both QTcD and QTc-SD were significantly greater in children with sinus arrhythmia than in those without (QTcD: 52.9 (17.4) v 40.9 (13.1); QTc-SD: 17.5 (5.9) v 13.2 (4.0); p < 0.001). Conclusions-As calculation of QTc dispersion is aVected by sinus arrhythmia, which is common in childhood, we suggest that QT dispersion should not be corrected for heart rate in children. (Heart 1998;80:77-79)

Prolonged cardiac repolarisation during spontaneous nocturnal hypoglycaemia in children and adolescents with type 1 diabetes

“…A recent study of children and adolescents reported a similar increased rate of prolonged QTc during daytime ECG monitoring in type 1 diabetic patients (23%) compared with matched control subjects (3%) [24]. While it may be difficult to compare QTc values between studies [11], figures from a large normative database indicate that prolonged QTc (>440 ms) is unusual in healthy children [25,26]. In our subjects, QTc was measured during sleep.…”

Methadone Safety: A Clinical Practice Guideline From the American Pain Society and College on Problems of Drug Dependence, in Collaboration With the Heart Rhythm Society

“…As in adults, data generally indicate that <5% of children have a QTc interval >450 ms. 44,79,97 In addition, as noted above, studies of siblings of children with long QT syndrome found increased risk of cardiovascular events at QTc intervals of 460 to 500 ms, though reported cases of torsades de pointes in children prescribed methadone are rare. Given the potential for increased risk and the availability of alternative opioids, the panel suggests that clinicians apply similar QTc parameters for use of methadone in children as in adults, until more evidence is available.…”

Electrocardiographic response to enzyme replacement therapy for Pompe disease

“…Normal values of QTd are reported to be 36 Ϯ 13.7 ms in 111 healthy children 5 days to 16 years old. 24 There is increased QTd in various cardiac diseases including patients with LVH and hypertrophic cardiomyopathy. 25,26 Although the mechanism by which QTd is increased in hypertrophic cardiomyopathy remains unclear, increased QTd has been shown to be a marker of increased risk for sudden cardiac death.…”