Dynamic QT Interval Changes from Supine to Standing in Healthy Children |
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Authors: | Audrey Dionne Anne Fournier Nagib Dahdah Dominic Abrams Paul Khairy Sylvia Abadir |
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Affiliation: | 1. Division of Cardiology, CHU mère-enfant Sainte-Justine, Université de Montréal, Montréal, Québec, Canada;2. Electrophysiology Service, Boston Children''s Hospital, Harvard University, Boston, MA, USA;3. Electrophysiology Service and Adult Congenital Heart Center, Montreal Heart Institute, Université de Montréal, Montréal, Québec, Canada |
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Abstract: | BackgroundQT-interval variations in response to exercise-induced increases in heart rate have been reported in children and adults in the diagnosis of long QT syndrome (LQTS). A quick standing challenge has been proposed as an alternative provocative test in adults, with no pediatric data yet available.MethodsA standing test was performed in 100 healthy children (mean age, 9.7 ± 3.1 years) after 10 minutes in a supine position with continuous electrocardiographic recording. QT intervals were measured at baseline, at maximal heart rate, at maximal QT, and at each minute of a 5-minute recovery while standing. Measurements were taken in leads II/V5 and were corrected for heart rate (QTc).ResultsOn standing, the heart rate increased by 29 ± 10 beats per minute (bpm). The QT interval was similar at baseline and on standing (394 ± 34 ms vs 394 ± 34 ms; P = 1.0). However, QTc increased from 426 ± 21 to 509 ± 41 ms (P < 0.001). The 95th percentile for QTc at baseline and maximal heart rate was 457 ms and 563 ms, respectively. At 1 minute of recovery, the QT interval was shorter (375 ± 31 ms) compared with baseline (394 ± 34 ms; P < 0.001) and standing (394 ± 34 ms; P < 0.001). QTc reached baseline values after 1 minute of recovery and remained stable thereafter (423 ± 23 ms at 1 minute; 426 ± 22 ms at 5 minutes; P = 1.0).ConclusionsThis first characterization of QTc changes on standing in children shows substantial alterations, which are greater than those seen in adults. Two-thirds of the children would have been misclassified as having LQTS by adult criteria, indicating the need to create child-specific standards. |
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Keywords: | Corresponding author: Dr Sylvia Abadir, Division of Cardiology, CHU mère-enfant Sainte-Justine, 3175 Chemin de la Côte Sainte Catherine, Montreal, QC H3T 1C5, Canada. Tel.: +1-514-345-4931 ×5402 fax: +1-51-345-4896. |
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