scholarly journals Problems with Bazett QTc correction in paediatric screening of prolonged QTc interval

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Irena Andršová ◽  
Katerina Hnatkova ◽  
Kateřina Helánová ◽  
Martina Šišáková ◽  
Tomáš Novotný ◽  
...  
Keyword(s):  
Heart Rate ◽  
Supine Position ◽  
Qt Interval ◽  
Qtc Interval ◽  
Healthy Children ◽  
Long Qt ◽  
Normal Children ◽  
Heart Rates ◽  
Qt Intervals ◽  
Qt Syndrome

Abstract Background Bazett formula is frequently used in paediatric screening for the long QT syndrome (LQTS) and proposals exist that using standing rather than supine electrocardiograms (ECG) improves the sensitivity of LQTS diagnosis. Nevertheless, compared to adults, children have higher heart rates (especially during postural provocations) and Bazett correction is also known to lead to artificially prolonged QTc values at increased heart rates. This study assessed the incidence of erroneously increased QTc values in normal children without QT abnormalities. Methods Continuous 12-lead ECGs were recorded in 332 healthy children (166 girls) aged 10.7 ± 2.6 years while they performed postural manoeuvring consisting of episodes (in the following order) of supine, sitting, standing, supine, standing, sitting, and supine positions, each lasting 10 min. Detailed analyses of QT/RR profiles confirmed the absence of prolonged individually corrected QTc interval in each child. Heart rate and QT intervals were measured in 10-s ECG segments and in each segment, QTc intervals were obtained using Bazett, Fridericia, and Framingham formulas. In each child, the heart rates and QTc values obtained during supine, sitting and standing positions were averaged. QTc durations by the three formulas were classified to < 440 ms, 440–460 ms, 460–480 ms, and > 480 ms. Results At supine position, averaged heart rate was 77.5 ± 10.5 beat per minute (bpm) and Bazett, Fridericia and Framingham QTc intervals were 425.3 ± 15.8, 407.8 ± 13.9, and 408.2 ± 13.1 ms, respectively. At sitting and standing, averaged heart rate increased to 90.9 ± 10.1 and 100.9 ± 10.5 bpm, respectively. While Fridericia and Framingham formulas showed only minimal QTc changes, Bazett correction led to QTc increases to 435 ± 15.1 and 444.9 ± 15.9 ms at sitting and standing, respectively. At sitting, Bazett correction identified 51, 4, and 0 children as having the QTc intervals 440–460, 460–480, and > 480 ms, respectively. At sitting, these numbers increased to 118, 11, and 1, while on standing these numbers were 151, 45, and 5, respectively. Irrespective of the postural position, Fridericia and Framingham formulas identified only a small number (< 7) of children with QT interval between 440 and 460 ms and no children with longer QTc. Conclusion During screening for LQTS in children, the use of Bazett formula leads to a high number of false positive cases especially if the heart rates are increased (e.g. by postural manoeuvring). The use of Fridericia formula can be recommended to replace the Bazett correction not only for adult but also for paediatric ECGs.

scholarly journals Problems with Bazett QTc Correction in Paediatric Screening of Prolonged QTc Interval

2020 ◽  
Author(s):  
Irena Andršová ◽  
Katerina Hnatkova ◽  
Kateřina Helánová ◽  
Martina Šišáková ◽  
Tomáš Novotný ◽  
...  
Keyword(s):  
Heart Rate ◽  
Supine Position ◽  
Qt Interval ◽  
Qtc Interval ◽  
Healthy Children ◽  
Long Qt ◽  
Normal Children ◽  
Heart Rates ◽  
Qt Intervals ◽  
Qt Syndrome

Abstract BackgroundBazett formula is frequently used in paediatric screening for the long QT syndrome (LQTS) and proposals exist that using standing rather than supine electrocardiograms (ECG) improves the sensitivity of LQTS diagnosis. Nevertheless, compared to adults, children have higher heart rates (especially during postural provocations) and Bazett correction is also known to lead to artificially prolonged QTc values at increased heart rates. This study assessed the incidence of erroneously increased QTc values in normal children without QT abnormalities.MethodsContinuous 12-lead ECGs were recorded in 332 healthy children (166 girls) aged 10.7±2.6 years while they performed postural manoeuvring consisting of episodes (in the following order) of supine, sitting, standing, supine, standing, sitting, and supine positions, each lasting 10 minutes. Detailed analyses of QT/RR profiles confirmed the absence of prolonged individually corrected QTc interval in each child. Heart rate and QT intervals were measured in 10-second ECG segments and in each segment, QTc intervals were obtained using Bazett, Fridericia, and Framingham formulas. In each child, the heart rates and QTc values obtained during supine, sitting and standing positions were averaged. QTc durations by the three formulas were classified to <440 ms, 440-460 ms, 460-480 ms, and >480 ms. ResultsAt supine position, averaged heart rate was 77.5±10.5 beat per minute (bpm) and Bazett, Fridericia and Framingham QTc intervals were 425.3±15.8, 407.8±13.9, and 408.2±13.1 ms, respectively. At sitting and standing, averaged heart rate increased to 90.9±10.1 and 100.9±10.5 bpm, respectively. While Fridericia and Framingham formulas showed only minimal QTc changes, Bazett correction led to QTc increases to 435±15.1 and 444.9±15.9 ms at sitting and standing, respectively. At sitting, Bazett correction identified 51, 4, and 0 children as having the QTc intervals 440-460, 460-480, and >480 ms, respectively. At sitting, these numbers increased to 118, 11, and 1, while on standing these numbers were 151, 45, and 5, respectively. Irrespective of the postural position, Fridericia and Framingham formulas identified only a small number (<7) of children with QT interval between 440 and 460 ms and no children with longer QTc.ConclusionDuring screening for LQTS in children, the use of Bazett formula leads to a high number of false positive cases especially if the heart rates are increased (e.g. by postural manoeuvring). The use of Fridericia formula can be recommended to replace the Bazett correction not only for adult but also for paediatric ECGs.

scholarly journals Response of the QT interval to mental and physical stress in types LQT1 and LQT2 of the long QT syndrome

Heart ◽  
2001 ◽  
Vol 86 (1) ◽  
pp. 39-44
Author(s):  
K J Paavonen ◽  
H Swan ◽  
K Piippo ◽  
L Hokkanen ◽  
P Laitinen ◽  
...  
Keyword(s):  
Heart Rate ◽  
Serum Potassium ◽  
Long Qt Syndrome ◽  
Qt Interval ◽  
Mental Stress ◽  
Physical Stress ◽  
Exercise Stress ◽  
Long Qt ◽  
Qt Intervals ◽  
Qt Syndrome

OBJECTIVETo study and compare the effects of mental and physical stress on long QT syndrome (LQTS) patients.DESIGNCase–control study.MAIN OUTCOME MEASURESQT intervals were measured from lead V3. Serum potassium and plasma catecholamine concentrations were also monitored.PATIENTS16 patients with type 1 LQTS (LQT1), 14 with type 2 LQTS (LQT2), both groups asymptomatic, and 14 healthy control subjects.INTERVENTIONSThree types of mental stress tests and a submaximal exercise stress test.RESULTSHeart rate responses to mental stress and exercise were similar in all groups. During mental stress, the mean QT interval shortened to a similar extent in controls (–29 ms), LQT1 patients (–34 ms), and LQT2 patients (–30 ms). During exercise, the corresponding QT adaptation to exercise stress was more pronounced (p < 0.01) in healthy controls (–47 ms) than in LQT1 (–38 ms) or LQT2 patients (–38 ms). During exercise changes in serum potassium concentrations were correlated to changes in QT intervals in controls, but not in LQTS patients. LQT1 and LQT2 patients did not differ in serum potassium, catecholamine or heart rate responses to mental or physical stress.CONCLUSIONSQT adaptation to mental and exercise stress in healthy people and in patients with LQTS is different. In healthy people QT adaptation is more sensitive to physical than to mental stress while no such diverging pattern was seen in asymptomatic LQTS patients.

Electrocardiogram screening of deaf children for long QT syndrome: are we following UK national guidelines?

2010 ◽  
Vol 125 (4) ◽  
pp. 354-356 ◽  
Author(s):  
S L Kang ◽  
C Jackson ◽  
W Kelsall
Keyword(s):  
Cochlear Implant ◽  
Long Qt Syndrome ◽  
Qt Interval ◽  
Deaf Children ◽  
National Guidelines ◽  
Long Qt ◽  
Local Practice ◽  
Qt Intervals ◽  
Centre Database ◽  
Qt Syndrome

AbstractIntroduction:Jervell–Lange-Nielsen syndrome is characterised by congenital deafness and a long QT interval on electrocardiography.Aim:(1) To survey UK national practice regarding electrocardiography screening of deaf children referred to cochlear implant centres, performed to evaluate for prolonged QT interval as recommended by national guidelines, and (2) to review local practice.Methods:Data were collected via a questionnaire sent to all UK cochlear implant centres, and via review of the medical records of a local cochlear implant centre database.Results:Eight (42 per cent) of the 19 cochlear implant centres surveyed performed electrocardiographic screening. Thirteen cases of long QT syndrome were reported in seven centres, with two related deaths. In our local cochlear implant centre, 14 (7.1 per cent) of 193 children had abnormal electrocardiograms; one definite long QT syndrome case and 13 borderline cases were identified.Conclusion:Despite clear national guidelines for electrocardiographic screening of deaf children, there is wide variation in practice. Our local practice of performing investigations, including electrocardiography, during magnetic resonance imaging sedation has been very successful. Electrocardiograms should be reviewed by trained clinicians, and corrected QT intervals should be calculated manually.

scholarly journals Evaluation of Tpeak–Tend and QT intervals in Chagas’ Disease, Chronic Phase and Normal Electrocardiogram

2020 ◽  
Vol 32 (4) ◽  
pp. 230-235
Author(s):  
Abilio Augusto Fragata Filho ◽  
Claudia da Silva Fragata ◽  
Angela Maria Lourenço ◽  
Cristiane Castro Faccini ◽  
João Ítalo Dias França
Keyword(s):  
Heart Rate ◽  
Chagas Disease ◽  
Qt Interval ◽  
Statistical Significance ◽  
Chronic Phase ◽  
Qtc Interval ◽  
Mean Values ◽  
Qt Intervals ◽  
Relationship Of ◽  
The Relationship

Introduction: Chagas’ disease lacks elements to predict which carriers will evolve into cardiac form and which will remain in undetermined form. Objective: To evaluate the relationship between electrocardiographic evolution and Tpeak–Tend and QT intervals, both corrected for heart rate, in chagasic patients with normal initial electrocardiogram. Method: Chagasic patients admitted to the institution until 2002 were retrospectively evaluated, and the electrocardiogram was normal at the first consultation. The Tpeak–Tend and QT intervals were measured in milliseconds at the V2 and V5 derivations, with the mean values corrected for heart rate (Bazett). The relationship of these values with the electrocardiographic evolution of the individuals was analyzed, considering the gender, time of evolution and whether they received benznidazole or not. Results: The corrected Tpeak–Tend interval showed no statistical significance among those who maintained or not normal electrocardiogram. The corrected QT interval, the treatment with benznidazole and the time of evolution showed significance for the maintenance of normal electrocardiogram. In the multivariate evaluation, treatment with benznidazole, the QTc interval and the time of evolution were independent variables for the maintenance of normal electrocardiogram. Conclusion: The Tpeak–Tend interval showed no predictor of electrocardiographic evolution. The increased QT interval favored changes.

scholarly journals Age-Gender Influence on the Rate-Corrected QT Interval and the QT-Heart Rate Relation in Families With Genotypically Characterized Long QT Syndrome

1997 ◽  
Vol 29 (1) ◽  
pp. 93-99 ◽  
Author(s):  
Michael H Lehmann ◽  
Katherine W Timothy ◽  
Debra Frankovich ◽  
Barbara S Fromm ◽  
Mark Keating ◽  
...  
Keyword(s):  
Heart Rate ◽  
Long Qt Syndrome ◽  
Qt Interval ◽  
Long Qt ◽  
Corrected Qt Interval ◽  
Gender Influence ◽  
Qt Syndrome ◽  
Rate Relation

“QT-Stunning:” the Abnormal Response of the QT Interval to Brisk Standing Persists Even as the Heart Rate Returns to Baseline in Patients with Long QT Syndrome

Heart Rhythm ◽  
2010 ◽  
Vol 7 (11) ◽  
pp. 1718-1719
Author(s):  
Arnon Adler ◽  
Sami Viskin ◽  
Christian van der Werf ◽  
Pieter Postema ◽  
Raphael Rosso ◽  
...  
Keyword(s):  
Heart Rate ◽  
Long Qt Syndrome ◽  
Qt Interval ◽  
Long Qt ◽  
Abnormal Response ◽  
Qt Syndrome

scholarly journals Light phase-restricted feeding slows basal heart rate to exaggerate the type-3 long QT syndrome phenotype in mice

2014 ◽  
Vol 307 (12) ◽  
pp. H1777-H1785 ◽  
Author(s):  
Elizabeth A. Schroder ◽  
Don E. Burgess ◽  
Cody L. Manning ◽  
Yihua Zhao ◽  
Arthur J. Moss ◽  
...  
Keyword(s):  
Heart Rate ◽  
Long Qt Syndrome ◽  
Time Of Day ◽  
Restricted Feeding ◽  
Light Phase ◽  
Long Qt ◽  
Qt Intervals ◽  
Qt Syndrome ◽  
Time Of Feeding ◽  
Type 3

Long QT syndrome type 3 (LQT3) is caused by mutations in the SCN5A-encoded Nav1.5 channel. LQT3 patients exhibit time of day-associated abnormal increases in their heart rate-corrected QT (QTc) intervals and risk for life-threatening episodes. This study determines the effects of uncoupling environmental time cues that entrain circadian rhythms (time of light and time of feeding) on heart rate and ventricular repolarization in wild-type (WT) or transgenic LQT3 mice ( Scn5a+/ΔKPQ). We used an established light phase-restricted feeding paradigm that disrupts the alignment among the circadian rhythms in the central pacemaker of the suprachiasmatic nucleus and peripheral tissues including heart. Circadian analysis of the RR and QT intervals showed the Scn5a+/ΔKPQ mice had QT rhythms with larger amplitudes and 24-h midline means and a more pronounced slowing of the heart rate. For both WT and Scn5a+/ΔKPQ mice, light phase-restricted feeding shifted the RR and QT rhythms ∼12 h, increased their amplitudes greater than twofold, and raised the 24-h midline mean by ∼10%. In contrast to WT mice, the QTc interval in Scn5a+/ΔKPQ mice exhibited time-of-day prolongation that was flipped after light phase-restricted feeding. The time-of-day changes in the QTc intervals of Scn5a+/ΔKPQ mice were secondary to a steeper power relation between their QT and RR intervals. We conclude that uncoupling time of feeding from normal light cues can dramatically slow heart rate to unmask genotype-specific differences in the QT intervals and aggravate the LQT3-related phenotype.

scholarly journals Comparison of formulae for heart rate correction of QT interval in exercise ECGs from healthy children

Heart ◽  
2001 ◽  
Vol 86 (2) ◽  
pp. 199-202
Author(s):  
A Benatar ◽  
T Decraene
Keyword(s):  
Heart Rate ◽  
Qt Interval ◽  
Heart Defects ◽  
New Drugs ◽  
Peak Exercise ◽  
Healthy Children ◽  
Long Qt ◽  
Correction Formula ◽  
Rr Interval ◽  
Heart Rate Correction

OBJECTIVETo investigate the differences in four formulae for heart rate correction of the QT interval in serial ECG recordings in healthy children undergoing a graded exercise test.SUBJECTS54 healthy children, median age 9.9 years (range 5.05–14.9 years), subjected to graded physical exercise (on a bicycle ergometer or treadmill) until heart rate reached > 85% of expected maximum for age.DESIGNECG was recorded at baseline, at maximum exercise, and at one, two, four, and six minutes after exercise. For each stage, a 12 lead digital ECG was obtained and printed. In each ECG, QT and RR interval were measured (lead II), heart rate was calculated, and QTc values were obtained using the Bazett, Hodges, Fridericia, and Framingham formulae. A pairedt test was used for comparison of QTc, QT, and RR interval at rest and peak exercise, and analysis of variance for all parameters for different stages for each formula.RESULTSFrom peak exercise to two minutes recovery there was a delay in QT lengthening compared with RR lengthening, accounting for differences observed with the formulae after peak exercise. At peak exercise, the Bazett and Hodges formulae led to prolongation of QTc intervals (p < 0.001), while the Fridericia and Framingham formulae led to shortening of QTc intervals (p < 0.001) until four minutes of recovery. The Bazett QTc shortened significantly at one minute after peak exercise.CONCLUSIONSThe practical meaning of QT interval measurements depends on the correction formula used. In studies investigating repolarisation changes (for example, in the long QT syndromes, congenital heart defects, or in the evaluation of new drugs), the use of an ad hoc selected heart rate correction formula may bias the results in either direction. The Fridericia and Framingham QTc values at one minute recovery from exercise may be useful in the assessment of long QT syndromes.

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