Two automatic QT algorithms compared with manual measurement in identification of long QT syndrome

Diamant, Ulla‐Britt; Winbo, Annika; Stattin, Eva‐Lena; Rydberg, Annika; Kesek, Milos; Jensen, Steen M.

doi:10.1016/j.jelectrocard.2009.09.008

Cited by 20 publications

(14 citation statements)

References 17 publications

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“…The end of the T‐wave was determined using the tangent method, 56 which involves locating the intersection between the line through the terminal descending part of the T‐wave and the isoelectric line (). This approach of using the tangent method in the vector magnitude lead produces more consistent measurements of the QT interval 57 . Of note, the U‐wave was not included in the measurement of the end of the T‐wave.…”

Section: Methodsmentioning

confidence: 99%

Differentiating Drug-Induced Multichannel Block on the Electrocardiogram: Randomized Study of Dofetilide, Quinidine, Ranolazine, and Verapamil

Johannesen

Vicente

Mason

et al. 2014

Clin Pharmacol Ther

216

282

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Block of the hERG potassium channel and prolongation of the QT interval are predictors of drug-induced torsade de pointes. However, drugs that block the hERG potassium channel may also block other channels that mitigate torsade risk. We hypothesized that the electrocardiogram can differentiate the effects of multichannel drug block by separate analysis of early repolarization (global J-Tpeak) and late repolarization (global Tpeak-Tend). In this prospective randomized controlled clinical trial, 22 subjects received a pure hERG potassium channel blocker (dofetilide) and three drugs that block hERG and either calcium or late sodium currents (quinidine, ranolazine, and verapamil). The results show that hERG potassium channel block equally prolongs early and late repolarization, whereas additional inward current block (calcium or late sodium) preferentially shortens early repolarization. Characterization of multichannel drug effects on human cardiac repolarization is possible and may improve the utility of the electrocardiogram in the assessment of drug-related cardiac electrophysiology.

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Section: Methodsmentioning

confidence: 99%

Differentiating Drug-Induced Multichannel Block on the Electrocardiogram: Randomized Study of Dofetilide, Quinidine, Ranolazine, and Verapamil

Johannesen

Vicente

Mason

et al. 2014

Clin Pharmacol Ther

216

282

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“…VCG provides both 3D QRST-derived "conventional" ECG measures [e.g., the QRS, QT, and T-peak to T-end (Tp-e) intervals], and information on other global aspects of VR, as reflected by T vector and T-vector loop morphology parameters. VCG also outlines the 3D relationship between depolarization and repolarization forces (3,19,24,25,29,30,31) and has proven superior to ECG for detection of VR changes in the long QT syndrome and of cardiac memory, as induced by ventricular pacing or appearing after Wolff-Parkinson-White ablation (6,30,31).…”

mentioning

confidence: 99%

Vectorcardiography analysis of the repolarization response to pharmacologically induced autonomic nervous system modulation in healthy subjects

Vahedi

Odenstedt

Hartford

et al. 2012

Journal of Applied Physiology

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Autonomic nervous system activity is essential for regulation of ventricular repolarization (VR) and plays an important role in several arrhythmogenic conditions. This study in 31 healthy adult subjects (16 men, 15 women) evaluated the VR response to pharmacologically modulated autonomic nervous system activity applying vectorcardiography (VCG) analysis. During continuous VCG recording, 0.01-0.1 μg·kg(-1)·min(-1) isoprenaline (Iso) was infused at an increasing flow rate until three targeted heart rates (HR) were reached. After Iso washout, one intravenous bolus of 0.04 mg/kg atropine was given followed by an intravenous bolus of 0.2 mg/kg propranolol. A 5-min steady-state VCG recording was analyzed for each of the seven phases (including baseline 1 and 2). Furthermore, during the first 4 min following atropine, six periods of 10-s VCG were selected for subanalysis to evaluate the time course of change. The analysis included QRS, QT, and T-peak to T-end intervals, measures of the QRS and T vectors and their relation, as well as T-loop morphology parameters. By increasing HR, Iso infusion decreased HR dependent parameters reflecting total heterogeneity of VR (T area) and action potential morphology (ventricular gradient). In contrast, Iso prolonged QT HR corrected according to Bazett and increased the T-peak to T-end-to-QT ratio to levels observed in arrhythmogenic conditions. HR acceleration after atropine was accompanied by a transient paradoxical QT prolongation and delayed HR adaptation of T area and ventricular gradient. In addition to the expected HR adaptation, the VR response to β-adrenoceptor stimulation with Iso and to muscarinic receptor blockade with atropine thus included alterations previously observed in congenital and acquired long QT syndromes, demonstrating substantial overlap between physiological and pathophysiological electrophysiology.

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“…In addition, it is stated that if the appropriateness of automated measurement can be proven, the guideline will be amended to incorporate such methods. In this regard, there have been several studies on the automatic QT interval algorithms that may prove to be more accurate and reliable method to measure the QT interval in the near future 8–12 . For example, the results of the recent studies focusing new automatic QT interval algorithms such as the vectorcardiography online automatic measurements or the QT sensor show the possibility of an accurate, efficient, and easily applied method to measure the QT interval 9,12 …”

Section: Discussionmentioning

confidence: 99%

Automated versus Manual Measurement of the QT Interval and Corrected QT Interval

Kasamaki

Ozawa

Ohta

et al. 2011

Noninvasive Electrocardiol

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We conclude that, for a thorough assessment of the QT/QTc interval, the tangent method or the differential threshold method appears to be suitable because of smaller interreader differences and better reproducibility. Correction of data should be done by readers who are experienced in measuring the QT interval. It is also important for electrocardiograms to have little noise and for a suitable heart rate and appropriate leads to be selected.

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Two automatic QT algorithms compared with manual measurement in identification of long QT syndrome

Cited by 20 publications

References 17 publications

Differentiating Drug-Induced Multichannel Block on the Electrocardiogram: Randomized Study of Dofetilide, Quinidine, Ranolazine, and Verapamil

Differentiating Drug-Induced Multichannel Block on the Electrocardiogram: Randomized Study of Dofetilide, Quinidine, Ranolazine, and Verapamil

Vectorcardiography analysis of the repolarization response to pharmacologically induced autonomic nervous system modulation in healthy subjects

Automated versus Manual Measurement of the QT Interval and Corrected QT Interval

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