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.

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 Safety and effectiveness of drug therapy for the acutely agitated patient (Part I)

2013 ◽  
pp. 127-136
Author(s):  
Gianluca Airoldi
Keyword(s):  
Heart Rate ◽  
Qt Interval ◽  
Physical Restraint ◽  
Safety Data ◽  
Surrogate Marker ◽  
Diagnostic Procedures ◽  
Torsades De Pointes ◽  
Long Qt ◽  
Drug Induced ◽  
Qt Interval Prolongation

Acute agitation occurs in a variety of medical and psychiatric conditions, and the management of agitated, abusive, or violent patients is a common problem in the emergency department. Rapid control of potentially dangerous behaviors by physical restraint and pharmacologic tranquillization is crucial to ensure the safety of the patient and health-care personnel and to allow diagnostic procedures and treatment of the underlying condition. The purpose of this article (the first in a 2-part series) is to review the extensive safety data published on the antipsychotic medications currently available for managing situations of this type, including older neuroleptics like haloperidol, chlorpromazine, and pimozide as well as a number of the newer atypical antipsychotics (olanzapine, risperidone, ziprasidone). Particular attention is focused on the ability of these drugs to lengthen the QT interval in surface electrocardiograms. This adverse effect is of major concern, especially in light of the reported relation between QT interval and the risk of sudden death. In patients with the congenital long-QT syndrome, a long QT interval is associated with a fatal paroxysmal ventricular arrhythmia knownas torsades de pointes. Therefore, careful evaluation of the QT-prolonging properties and arrhythmogenic potential of antipsychotic drugs is urgently needed. Clinical assessment of drug-induced QT-interval prolongation is strictly dependent on the quality of electrocardiographic data and the appropriateness of electrocardiographic analyses. Unfortunately, measurement imprecision and natural variability preclude a simple use of the actually measured QT interval as a surrogate marker of drug-induced proarrhythmia. Because the QT interval changes with heart rate, a rate-corrected QT interval (QTc) is commonly used when evaluating a drug’s effect. In clinical settings, themost widely used formulas for rate-correction are those of Bazett (QTc=QT/RR^0.5) and Fridericia (QTc=QT/RR^0.33), both of which standardize themeasuredQTinterval to an RRinterval of 1 s (heart rate of 60 bpm).However, QT variability can also be influenced by other factors that are more difficult to measure, including body fat, meals, psycho-physical distress, and circadian and seasonal fluctuations.

scholarly journals Cardiomyocyte Deletion of Bmal1 Exacerbates QT- and RR-Interval Prolongation in Scn5a+/ΔKPQ Mice

2021 ◽  
Vol 12 ◽  
Author(s):  
Elizabeth A. Schroder ◽  
Jennifer L. Wayland ◽  
Kaitlyn M. Samuels ◽  
Syed F. Shah ◽  
Don E. Burgess ◽  
...  
Keyword(s):  
Heart Rate ◽  
Circadian Clock ◽  
Qt Interval ◽  
Adult Mouse ◽  
Interval Prolongation ◽  
Rr Interval ◽  
Adult Cardiomyocytes ◽  
Channel Expression ◽  
Cell Type Specific

Circadian rhythms are generated by cell autonomous circadian clocks that perform a ubiquitous cellular time-keeping function and cell type-specific functions important for normal physiology. Studies show inducing the deletion of the core circadian clock transcription factor Bmal1 in adult mouse cardiomyocytes disrupts cardiac circadian clock function, cardiac ion channel expression, slows heart rate, and prolongs the QT-interval at slow heart rates. This study determined how inducing the deletion of Bmal1 in adult cardiomyocytes impacted the in vivo electrophysiological phenotype of a knock-in mouse model for the arrhythmogenic long QT syndrome (Scn5a+/ΔKPQ). Electrocardiographic telemetry showed inducing the deletion of Bmal1 in the cardiomyocytes of mice with or without the ΔKPQ-Scn5a mutation increased the QT-interval at RR-intervals that were ≥130 ms. Inducing the deletion of Bmal1 in the cardiomyocytes of mice with or without the ΔKPQ-Scn5a mutation also increased the day/night rhythm-adjusted mean in the RR-interval, but it did not change the period, phase or amplitude. Compared to mice without the ΔKPQ-Scn5a mutation, mice with the ΔKPQ-Scn5a mutation had reduced heart rate variability (HRV) during the peak of the day/night rhythm in the RR-interval. Inducing the deletion of Bmal1 in cardiomyocytes did not affect HRV in mice without the ΔKPQ-Scn5a mutation, but it did increase HRV in mice with the ΔKPQ-Scn5a mutation. The data demonstrate that deleting Bmal1 in cardiomyocytes exacerbates QT- and RR-interval prolongation in mice with the ΔKPQ-Scn5a mutation.

Heart rate correction of the QT interval: A nonparametric individualized approach

2008 ◽  
Vol 58 (2) ◽  
pp. 160
Author(s):  
G. Greco ◽  
A. Russu ◽  
C. Arrigoni ◽  
P. Magni ◽  
G. De Nicolao ◽  
...  
Keyword(s):  
Heart Rate ◽  
Qt Interval ◽  
Individualized Approach ◽  
Heart Rate Correction

Influence of age, the autonomic nervous system and anxiety on QT-interval variability

2001 ◽  
Vol 101 (4) ◽  
pp. 429-438 ◽  
Author(s):  
Gianfranco PICCIRILLO ◽  
Mauro CACCIAFESTA ◽  
Marco LIONETTI ◽  
Marialuce NOCCO ◽  
Vincenza DI GIUSEPPE ◽  
...  
Keyword(s):  
Heart Rate ◽  
Qt Interval ◽  
Spectral Power ◽  
Low Frequency ◽  
Elderly Subjects ◽  
Rr Interval ◽  
T Wave ◽  
Qt Variability ◽  
Qt Interval Variability ◽  
Sympathetic Stress

As QT variability increases and heart rate variability diminishes, the QT variability index (QTVI)-a non-invasive measure of beat-to-beat fluctuations in QT interval on a single ECG lead-shows a trend towards positive values. Increased QT variability is a risk factor for sudden death. Aging lengthens the QT interval and reduces RR-interval variability. In the present study we investigated the influence of aging and the autonomic nervous system on QT-interval variability in healthy subjects. We studied 143healthy subjects, and divided them into two age ranges (younger and older than 65 years). For each subject we measured two QTVIs: from the q wave to the end of the T wave (QTeVI) and to the apex of the T wave (QTaVI). Both indexes were calculated at baseline and after sympathetic stress. In 10 non-elderly subjects, both QTVIs were determined after β-adrenoreceptor blockade induced by intravenous infusion of propranolol or sotalol. The QTVI was higher in elderly than in younger subjects (P < 0.001). QTVIs obtained during sympathetic stress remained unchanged in the elderly, but became more negative in the younger group (P < 0.05). QTeVI and QTaVI at baseline were correlated positively with age (P < 0.01) and anxiety scores (P < 0.05), but inversely with the low-frequency spectral power of RR-interval variability (P < 0.001). QTVIs were higher in subjects with higher anxiety scores. In younger subjects, sotalol infusion increased both QTVIs significantly, whereas propranolol infusion did not. In conclusion, aging increases QT-interval variability. Whether this change is associated with an increased risk of sudden death remains unclear. The association of abnormal QT-interval variability with anxiety and with reduced low-frequency spectral power of heart rate variability merits specific investigation. In healthy non-elderly subjects, acute sympathetic stress (tilt) decreases the QTVI. β-Adrenoreceptor blockade inhibits this negative trend, thus showing its sympathetic origin. Because a negative trend in QTVI induced by sympathetic stress increases only in younger subjects, it could represent a protective mechanism that is lost with aging.

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