Comparison of methods for correcting QT interval in athletes and young people: A systematic review

Screening elite athletes for conditions associated with sudden cardiac death is recommended by numerous international guidelines. Current athlete electrocardiogram interpretation criteria recommend the Bazett formula (QTcB) for correcting QT interval. However, other formulae may perform better at lower and higher heart rates (HR). This review aimed to examine the literature on various QT correction methods in athletes and young people aged 14-35 years and determine the most accurate method of calculating QTc in this population. A systematic review of MEDLINE, EMBASE, Scopus, and SportDiscus was performed. Papers comparing at least two different methods of QT interval correction in athletes or young people were included. Quality and risk of bias were assessed using a standardized tool. The search strategy identified 545 papers, of which 10 met the criteria and were included. Nine of these studies concluded that QTcB was least reliable for removing the effect of HR and was inaccurate at both high (>90 beats per min [BPM]) and low (<60 BPM) HRs. No studies supported the use of QTcB in athletes and young people. Alternative QT correction algorithms such as Fridericia (QTcF) produce more accurate correction of QT interval at HRs seen in athletes and young people. QTcB is less accurate at lower and higher HRs. QTcF has been shown to be more accurate in these HR ranges and may be preferred to QTcB for QTc calculation in athletes and young people. However, accurate QTc reference values for discrete HRs using alternative algorithms are not well established and require further research.

Frequency of QTc Interval Prolongation in Children and Adults with Williams Syndrome

QTc prolongation (≥ 460 ms), according to Bazett formula (QTcB), has been identified to be increased in Williams syndrome (WS) and suggested as a potential cause of increased risk of sudden cardiac death. The Bazett formula tends to overestimate QTc in higher heart rates. We performed a retrospective chart review of WS patients with ≥ 1 electrocardiogram (EKG) with sinus rhythm, no evidence of bundle branch blocks, and measurable intervals. A total of 280 EKGs from 147 patients with WS were analyzed and 123 EKGs from 123 controls. The QTc was calculated using Bazett formula. The average QTcB for individuals with WS and controls was 444 ± 24 ms and 417 ± 26 ms, respectively (p < 0.001). In our WS cohort 34.4% had at least 1 EKG with a QTcB ≥ 460 ms. The mean heart rate (HR) from patients with WS was significantly higher than controls (96 bpm vs 76 bpm, p < 0.001). Linear regression showed that HR contributed 27% to QTcB prolongation in the patients with WS. Patients with WS have a mean QTcB in the normal range but higher than controls, and a higher than expected frequency of QTc ≥ 460 ms compared to the general population. HR is also higher in WS and contributes modestly to the WS QTcB prolongation. Future studies are needed to assess if these findings contribute risk to sudden cardiac death but in the interim we recommend routine EKG testing, especially when starting QTc prolonging medications.

Estimation of cardiac QTc intervals in people prescribed antipsychotics: a comparison of correction factors

BACKGROUND

A prolonged electrocardiogram (ECG) QT interval is associated with cardiac events and increased mortality. Antipsychotics can prolong the QT interval. The QT interval requires correction (QTc) for heart rate using a formula or QT-nomogram. The QT and QTc can be calculated automatically by the ECG machine or manually; however, machine-measured QT(c) intervals may be inaccurate.

OBJECTIVE

We aimed to investigate the mean QTc and proportion of prolonged QTc intervals in people taking antipsychotic medicines.

METHODS

We conducted an observational retrospective chart review and data analysis of all consecutive patients taking antipsychotics, with an ECG record, admitted to the psychiatric unit of a large tertiary hospital in Brisbane, Australia, between 1 January 2017 and 30 January 2019. We investigated the mean QTc of people taking antipsychotics to determine differences using (a) machine versus manual QT interval measurement and (b) QTc correction formulae (Bazett, Fridericia, Framingham, Hodges and Rautaharju) and the QT-nomogram. We also determined the number of people with a prolonged QTc using different methods and compared rates of prolonged QTc with antipsychotic monotherapy and polypharmacy.

RESULTS

Of 920 included people, the mean (±SD) machine-measured, Bazett-corrected QT interval (recorded from the ECG) was 435 ms (±27), significantly longer (p < 0.001) than the mean manually measured corrected QT intervals with Fridericia 394 ms (±24), Framingham 395 ms (±22), Hodges 398 ms (±22) and Rautaharju 400 ms (±24) formulae. There were significantly more people with a prolonged QTc using machine-measured QT and the Bazett formula (12.0%, 110/920) when compared with manually measured QT and the Fridericia formula (2.2%, 20/920) or QT-nomogram (0.7%, 6/920). Rates of QTc prolongation did not differ between people taking antipsychotic polypharmacy compared with monotherapy.

CONCLUSION

Machine-measured QTc using the Bazett formula overestimates the QTc interval length and number of people with a prolonged QTc, compared with other formulae and the QT-nomogram. We recommend manually measuring the QT and correcting with the Fridericia formula or QT-nomogram prior to modifying antipsychotic therapies.

QT Assessment in Early Drug Development: The Long and the Short of It

The QT interval occupies a pivotal role in drug development as a surface biomarker of ventricular repolarization. The electrophysiologic substrate for QT prolongation coupled with reports of non-cardiac drugs producing lethal arrhythmias captured worldwide attention from government regulators eventuating in a series of guidance documents that require virtually all new chemical compounds to undergo rigorous preclinical and clinical testing to profile their QT liability. While prolongation or shortening of the QT interval may herald the appearance of serious cardiac arrhythmias, the positive predictive value of an abnormal QT measurement for these arrhythmias is modest, especially in the absence of confounding clinical features or a congenital predisposition that increases the risk of syncope and sudden death. Consequently, there has been a paradigm shift to assess a compound's cardiac risk of arrhythmias centered on a mechanistic approach to arrhythmogenesis rather than focusing solely on the QT interval. This entails both robust preclinical and clinical assays along with the emergence of concentration QT modeling as a primary analysis tool to determine whether delayed ventricular repolarization is present. The purpose of this review is to provide a comprehensive understanding of the QT interval and highlight its central role in early drug development.

Significance of prolonged QTc in acute exacerbations of COPD requiring hospitalization

Background

A prolonged QT interval is associated with increased risk of Torsade de Pointes and cardiovascular death. The prevalence and clinical relevance of QT prolongation in acute exacerbations of COPD (AECOPD), with high risk for cardiac morbidity and mortality, is currently unclear.

Methods

A dual cross-sectional study strategy was therefore designed. A retrospective study evaluated 140 patients with an AECOPD requiring hospitalization, half of which had prolonged QTc on the admission ECG. Univariate and multivariate analyses were conducted to determine associated factors; Kaplan–Meier and Cox regression analyses to assess prognostic significance. A prospective study evaluated 180 pulmonary patients with acute respiratory problems requiring hospitalization, to determine whether a prolonged QTc at admission represents an AECOPD-specific finding and to investigate the change in QTc-duration during hospitalization.

Results

Retrospectively, hypokalemia, cardiac troponin T and conductance abnormalities on ECG were significantly and independently associated with QTc prolongation. A prolonged QTc was associated with increased all-cause mortality (HR 2.698 (95% CI 1.032–7.055), p=0.043), however, this association was no longer significant when corrected for age, FEV₁ and cardiac troponin T. Prospectively, QTc prolongation was observed in 1/3 of the patients diagnosed with either an AECOPD, lung cancer, pulmonary infection or miscellaneous acute pulmonary disease, and was not more prevalent in AECOPD. The QTc-duration decreased significantly during hospitalization in patients with and without COPD.

Conclusion

A prolonged QTc is a marker of underlying cardiovascular disease during an AECOPD. It is not COPD-specific, but a common finding during the acute phase of a pulmonary disease requiring urgent hospital admission.

[Comparison of four formulas of adjusting QT interval for the heart rate in young elite athletes]

PURPOSE

Sudden cardiac death in young athlete is always tragic. Some international guidelines recommend the realization of an electrocardiogram before practicing competitive sports to carry out the risk of sudden cardiac death due to genetic cardiopathy like QT long syndrome. Unfortunately, the diagnosis can be difficult because intensive sport can increase the QT interval over normal recognized values for sedentary people. Using a QT correction formula free of heart rate appears essential.

PATIENTS AND METHODS

Four hundred and forty-six young athletes (aged 10 to 18) had an electrocardiogram. QT intervals were measured and four methods were used to correct the QT interval for heart rate.

RESULTS

The Bazett formula performed the worst in terms of rate adjustment success. Hodges and Fridericia formulas are the best both in males and females, independently of age. Female had longer QTc intervals than males.

CONCLUSION

The most widely used Bazett formula should be surrendered whereas Hodges and Fridericia formulas should be preferred, particularly in young athletes.