Sources of QTc variability: Implications for effective ECG monitoring in clinical practice

Hnatkova, Katerina; Malik, Marek

doi:10.1111/anec.12730

Cited by 11 publications

(9 citation statements)

References 47 publications

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“…Heart rate (RR interval values) and uncorrected QT measurements were performed by one electrophysiologist in order to reduce any inter‐operator variability (S.‐S. B); 14 they were entered into a database and QT intervals were rate corrected using Bazett’s correction (heart rate < 90 beats per minute), and Fridericia’s correction (heart rate ≥ 90 beats per minute). For manual measurements, all 12 leads were visually analyzed; the lead where the QT interval was the most readily measured was selected for measurement (usually the precordial leads V2 or V3).…”

Section: Methodsmentioning

confidence: 99%

“…For manual measurements, all 12 leads were visually analyzed; the lead where the QT interval was the most readily measured was selected for measurement (usually the precordial leads V2 or V3). The QT interval was measured at this lead, and thereafter compared to other leads to ensure that the longest QT interval of all leads was recorded according to the guidelines 14–16 . For each 12 lead‐ECG, automated QTc measurements, and manual measurements as described above, were compared.…”

Section: Methodsmentioning

confidence: 99%

“…The QT interval was measured at this lead, and thereafter compared to other leads to ensure that the longest QT interval of all leads was recorded according to the guidelines. [14][15][16] For each 12 lead-ECG, automated QTc measurements, and manual measurements as described above, were compared. For automated ECG measurements, the proprietary QT algorithms contained in the ECG machines (General Electrics Marquette Mac 5500 HD and 1200 ST, GE Medical systems, Milwaukee, Wis.) were used.…”

Section: Qt Measurementmentioning

confidence: 99%

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QT Interval Prolongation Under Hydroxychloroquine/Azithromycin Association for Inpatients With SARS‐CoV‐2 Lower Respiratory Tract Infection

Bun

Taghji²,

Courjon

et al. 2020

Clin Pharma and Therapeutics

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Association between Hydroxychloroquine (HCQ) and Azithromycin (AZT) is under evaluation for patients with lower respiratory tract infection (LRTI) caused by the Severe Acute Respiratory Syndrome (SARS-CoV-2). Both drugs have a known torsadogenic potential, but sparse data are available concerning QT prolongation induced by this association. Our objective was to assess for COVID-19 LRTI variations of QT interval under HCQ/AZT in patients hospitalized, and to compare manual versus automated QT measurements. Before therapy initiation, a baseline 12 lead-ECG was electronically sent to our cardiology department for automated and manual QT analysis (Bazett and Fridericia's correction), repeated 2 days after initiation. According to our institutional protocol (Pasteur University Hospital), HCQ/ AZT was initiated only if baseline QTc ≤ 480ms and potassium level> 4.0 mmol/L. From March 24 th to April 20 th 2020, 73 patients were included (mean age 62 ± 14 years, male 67%). Two patients out of 73 (2.7%) were not eligible for drug initiation (QTc ≥ 500 ms). Baseline average automated QTc was 415 ± 29 ms and lengthened to 438 ± 40 ms after 48 hours of combined therapy. The treatment had to be stopped because of significant QTc prolongation in two out of 71 patients (2.8%). No drug-induced life-threatening arrhythmia, nor death was observed. Automated QTc measurements revealed accurate in comparison with manual QTc measurements. In this specific population of inpatients with COVID-19 LRTI, HCQ/AZT could not be initiated or had to be interrupted in less than 6% of the cases.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Qt Measurementmentioning

confidence: 99%

See 1 more Smart Citation

QT Interval Prolongation Under Hydroxychloroquine/Azithromycin Association for Inpatients With SARS‐CoV‐2 Lower Respiratory Tract Infection

Bun

Taghji²,

Courjon

et al. 2020

Clin Pharma and Therapeutics

View full text Add to dashboard Cite

show abstract

“…It is surely true that QTc interval changes may reflect not only treatment-related and channelopathy-based repolarisation abnormalities 2 but also electrolyte differences 15 , fever 16 , hormonal changes 17 , and alteration in autonomic and central nervous status 18 . Nevertheless, it is also apparent that imprecisions of QT interval measurement and inaccuracies of its heart rate correction may substantially contribute to an increased variability of measured QTc values 19 .…”

Section: Introductionmentioning

confidence: 99%

Influence of heart rate correction formulas on QTc interval stability

Andršová

Hnatkova²,

Šišáková

et al. 2021

Sci Rep

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Monitoring of QTc interval is mandated in different clinical conditions. Nevertheless, intra-subject variability of QTc intervals reduces the clinical utility of QTc monitoring strategies. Since this variability is partly related to QT heart rate correction, 10 different heart rate corrections (Bazett, Fridericia, Dmitrienko, Framingham, Schlamowitz, Hodges, Ashman, Rautaharju, Sarma, and Rabkin) were applied to 452,440 ECG measurements made in 539 healthy volunteers (259 females, mean age 33.3 ± 8.4 years). For each correction formula, the short term (5-min time-points) and long-term (day-time hours) variability of rate corrected QT values (QTc) was investigated together with the comparisons of the QTc values with individually corrected QTcI values obtained by subject-specific modelling of the QT/RR relationship and hysteresis. The results showed that (a) both in terms of short-term and long-term QTc variability, Bazett correction led to QTc values that were more variable than the results of other corrections (p < 0.00001 for all), (b) the QTc variability by Fridericia and Framingham corrections were not systematically different from each other but were lower than the results of other corrections (p-value between 0.033 and < 0.00001), and (c) on average, Bazett QTc values departed from QTcI intervals more than the QTc values of other corrections. The study concludes that (a) previous suggestions that Bazett correction should no longer be used in clinical practice are fully justified, (b) replacing Bazett correction with Fridericia and/or Framingham corrections would improve clinical QTc monitoring, (c) heart rate stability is needed for valid QTc assessment, and (d) development of further QTc corrections for day-to-day use is not warranted.

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“…Although correcting QT interval duration for heart rate (or corresponding RR interval) derived from QT/RR hysteresis assessment leads to a substantial reduction in QTc variability (Malik et al, 2008a;Jacquemet et al, 2011Jacquemet et al, , 2014Hnatkova and Malik, 2020), the variability is not entirely eliminated as also demonstrated by the positive (i.e., > 0) regression residuals that we report (also note that the vertical width of the scatter diagram shown in Figure 15 spans some 10 ms). There are different sources of such a variability.…”

Section: Qt/qtc Variabilitymentioning

confidence: 63%

Sex and Rate Change Differences in QT/RR Hysteresis in Healthy Subjects

et al. 2022

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While it is now well-understood that the extent of QT interval changes due to underlying heart rate differences (i.e., the QT/RR adaptation) needs to be distinguished from the speed with which the QT interval reacts to heart rate changes (i.e., the so-called QT/RR hysteresis), gaps still exist in the physiologic understanding of QT/RR hysteresis processes. This study was designed to address the questions of whether the speed of QT adaptation to heart rate changes is driven by time or by number of cardiac cycles; whether QT interval adaptation speed is the same when heart rate accelerates and decelerates; and whether the characteristics of QT/RR hysteresis are related to age and sex. The study evaluated 897,570 measurements of QT intervals together with their 5-min histories of preceding RR intervals, all recorded in 751 healthy volunteers (336 females) aged 34.3 ± 9.5 years. Three different QT/RR adaptation models were combined with exponential decay models that distinguished time-based and interval-based QT/RR hysteresis. In each subject and for each modelling combination, a best-fit combination of modelling parameters was obtained by seeking minimal regression residuals. The results showed that the response of QT/RR hysteresis appears to be driven by absolute time rather than by the number of cardiac cycles. The speed of QT/RR hysteresis was found decreasing with increasing age whilst the duration of individually rate corrected QTc interval was found increasing with increasing age. Contrary to the longer QTc intervals, QT/RR hysteresis speed was faster in females. QT/RR hysteresis differences between heart rate acceleration and deceleration were not found to be physiologically systematic (i.e., they differed among different healthy subjects), but on average, QT/RR hysteresis speed was found slower after heart rate acceleration than after rate deceleration.

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Sources of QTc variability: Implications for effective ECG monitoring in clinical practice

Cited by 11 publications

References 47 publications

QT Interval Prolongation Under Hydroxychloroquine/Azithromycin Association for Inpatients With SARS‐CoV‐2 Lower Respiratory Tract Infection

QT Interval Prolongation Under Hydroxychloroquine/Azithromycin Association for Inpatients With SARS‐CoV‐2 Lower Respiratory Tract Infection

Influence of heart rate correction formulas on QTc interval stability

Sex and Rate Change Differences in QT/RR Hysteresis in Healthy Subjects

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