Comparison of automatic QT measurement techniques in the normal 12 lead electrocardiogram.

McLaughlin, Neil; Campbell, R. W. F.; Murray, Alan

doi:10.1136/hrt.74.1.84

Cited by 116 publications

(61 citation statements)

References 12 publications

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“…Templates representing the average PQRST complex in the segments were generated. The end of the T wave (T end ) in each template was determined automatically using the slope intersect method [17]. The QT interval was calculated as the time from the beginning of the Q wave to T end in each template.…”

Section: Ecg Measurementsmentioning

confidence: 99%

QT interval prolongation during spontaneous episodes of hypoglycaemia in type 1 diabetes: the impact of heart rate correction

et al. 2010

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Aims/hypothesis Prolongation of the heart rate corrected QT interval (QTc) is seen during episodes of hypoglycaemia in type 1 diabetes. We studied the relationship between spontaneous hypoglycaemia and the QT interval and hypothesised that the choice of heart rate correction affects the observed change in QTc. Methods Twenty-one participants with type 1 diabetes (aged 58±10 years with duration of diabetes 34±12 years) had continuous glucose and ECG monitoring for 72 h. QT and RR intervals were measured during hypoglycaemia (blood glucose or continuous glucose measurements ≤3.5 mmol/l) and compared with euglycaemia (5-12 mmol/l). QT intervals were measured using the semi-automated tangent method from signal-averaged ECG and corrected using Bazett's formula, Fridericia's formula, the nomogram method and a linear subject-specific method.Results Hypoglycaemia was present in 14 participants. With Bazett's formula, QTc changed significantly from euglycaemia to hypoglycaemia (422±30 vs 432±33 ms; p=0.02). Heart rate, QT intervals and QTc corrected with formulas other than Bazett's were not associated with a significant change (p= 0.07-0.29). During hypoglycaemia, significantly lower values of QTc compared with the subject-specific method were seen for Fridericia's formula (p=0.02) and the nomogram method (p=0.04). Conclusions/interpretation Spontaneous hypoglycaemia was associated with a modest increase in QTc. Bazett's formula resulted in overcorrection of QTc while both Fridericia's formula and the nomogram method undercorrected the QTc compared with the subject-specific method during hypoglycaemia. The results may indicate that the use of a fixed heart rate correction formula can lead to misleading results in investigations of spontaneous hypoglycaemia.

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Section: Ecg Measurementsmentioning

confidence: 99%

QT interval prolongation during spontaneous episodes of hypoglycaemia in type 1 diabetes: the impact of heart rate correction

et al. 2010

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“…The QT interval was defined as the onset of QRS to the point of return of the T wave to the isoelectric line using the maximum slope technique. The QT interval was measured in all leads where the terminal segment of the T wave was clearly demarcated (11), with the longest interval in any lead used as the representative QT interval. The RR interval was calculated from the preceding two consecutive R waves.…”

Section: Ecg Acquisitionmentioning

confidence: 99%

Torsades de pointes during complete atrioventricular block: Genetic factors and electrocardiogram correlates

Subbiah

Gollob

Gula

et al. 2010

Canadian Journal of Cardiology

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V entricular arrhythmias have been reported in the setting of complete atrioventricular (AV) block since 1918 (1). In 1966, Dessertenne (2) described such an arrhythmia as torsades de pointes (TdP), a polymorphic ventricular tachycardia preceded by QT interval prolongation, now known to be caused by congenital or acquired long QT syndrome (LQTS) (3).Bradyarrhythmias caused by high-grade AV block are common. It is, however, infrequent that bradyarrhythmias are associated with QT interval prolongation and TdP phenomena (4-6). In patients with bradycardia-induced TdP, a number of electrocardiogram (ECG) parameters during bradycardia correlate with increased risk of TdP, including the QT interval (4-6), T wave morphology and T peak to T end (T p -T e ) (6). Although ECG parameters can be reasonable predictors of TdP in bradyarrhythmias (4-6), there are limited data on cellular or genetic mechanisms of bradycardia-induced TdP (7,8).We hypothesized that patients with bradycardia-mediated QT arrhythmia may have latent congenital LQTS or a vulnerable genetic polymorphism. In the setting of AV block, reduced repolarization reserve may be 'unmasked' in patients, manifesting as QT interval prolongation and TdP. Such an occult form of LQTS has previously been reported among patients with undiagnosed congenital LQTS who develop marked QT interval prolongation and TdP when exposed to QT-prolonging drugs (9,10). Moreover, the development of TdP in the setting of AV block may identify ion channel mutations that have a propensity to cause TdP and sudden cardiac death. INtRodUCtIoN: Atrioventricular (AV) block is infrequently associated with QT prolongation and torsades de pointes (TdP). It was hypothesized that patients with AV block-mediated QT-related arrhythmia may have latent congenital long QT syndrome or a vulnerable genetic polymorphism. Methods: Eleven patients with complete AV block and TdP were prospectively identified. Patients underwent assessment, resting electrocardiography and telemetry at baseline, during AV block and pre-TdP. Genetic testing of KCNH2, KCNQ1, KCNE1, KCNE2 and SCN5A was performed. Thirty-three patients with AV block without TdP were included for comparison. ResULts: Genetic variants were identified in 36% of patients with AV block and TdP. Patients with AV block who developed TdP had significantly longer mean (± SD) corrected QT intervals (440±93 ms versus 376±40 ms, P=0.048) and T peak to T end (T p -T e ) intervals (147±25 ms versus 94±25 ms, P=0.0001) than patients with AV block alone. In patients with a genetic variant, there was a significant increase in T p -T e intervals at baseline, in AV block and pre-TdP compared with those who were genotype negative. A personal or family history of syncope or sudden death was more likely observed in patients with a genetic variant. CoNCLUsIoNs: TdP in the setting of AV block may be a marker of an underlying genetic predisposition to reduced repolarization reserve. The T p -T e interval at baseline, in AV block and pre-TdP may predict a genetic mutation ...

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“…В современных системах ХМ для автоматического анализа интервала QT используется несколько методов определения окончания Т зубца [69]. Интервала QT у здоровых пациентов, опреде-ленный пороговым методом, практически не отлича-лись от значений QT, измеренных вручную [70,71]. У больных с сердечно-сосудистой патологией, приво- [73], где автоматический анализ интервала QT проводился у 40 молодых людей в возрасте 28±9 лет парабаличе-ским методом, были получены QTср 343±24 мсек у мужчин и 343±23 мсек для женщин, QTс составил 400±20 мсек для мужчин и 420±17 мсек для женщин, а QTр ср.…”

Section: оценка интервала Qt при хмunclassified

National Russian Guidelines on Application of the Methods of Holter Monitoring in Clinical Practice

Макаров¹,

Комолятова²,

Куприянова³

et al. 2014

Russ J Cardiol

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Comparison of automatic QT measurement techniques in the normal 12 lead electrocardiogram.

Abstract: Different QT measurement techniques produced results which were influenced, to varying degrees, by filtering and technique variables. This is relevant for the inter-comparison of studies using different techniques. Technique TH, a common approach, is not recommended.

Cited by 116 publications

References 12 publications

QT interval prolongation during spontaneous episodes of hypoglycaemia in type 1 diabetes: the impact of heart rate correction

QT interval prolongation during spontaneous episodes of hypoglycaemia in type 1 diabetes: the impact of heart rate correction

Torsades de pointes during complete atrioventricular block: Genetic factors and electrocardiogram correlates

National Russian Guidelines on Application of the Methods of Holter Monitoring in Clinical Practice

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