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J Am Heart Assoc. 2016 Jun 17;5(6). pii: e003264. doi: 10.1161/JAHA.116.003264.

Which QT Correction Formulae to Use for QT Monitoring?

Author information

1
Department of Cardiovascular Sciences, University of Leuven, Belgium Department of Cardiology, University Hospitals Leuven, Leuven, Belgium bert.vandenberk@med.kuleuven.be.
2
Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, Belgium.
3
Department of Cardiovascular Sciences, University of Leuven, Belgium Department of Cardiology, University Hospitals Leuven, Leuven, Belgium.
4
Department of Neurosciences, University of Leuven, Belgium.

Abstract

BACKGROUND:

Drug safety precautions recommend monitoring of the corrected QT interval. To determine which QT correction formula to use in an automated QT-monitoring algorithm in our electronic medical record, we studied rate correction performance of different QT correction formulae and their impact on risk assessment for mortality.

METHODS AND RESULTS:

All electrocardiograms (ECGs) in patients >18 years with sinus rhythm, normal QRS duration and rate <90 beats per minute (bpm) in the University Hospitals of Leuven (Leuven, Belgium) during a 2-month period were included. QT correction was performed with Bazett, Fridericia, Framingham, Hodges, and Rautaharju formulae. In total, 6609 patients were included (age, 59.8±16.2 years; 53.6% male and heart rate 68.8±10.6 bpm). Optimal rate correction was observed using Fridericia and Framingham; Bazett performed worst. A healthy subset showed 99% upper limits of normal for Bazett above current clinical standards: men 472 ms (95% CI, 464-478 ms) and women 482 ms (95% CI 474-490 ms). Multivariate Cox regression, including age, heart rate, and prolonged QTc, identified Framingham (hazard ratio [HR], 7.31; 95% CI, 4.10-13.05) and Fridericia (HR, 5.95; 95% CI, 3.34-10.60) as significantly better predictors of 30-day all-cause mortality than Bazett (HR, 4.49; 95% CI, 2.31-8.74). In a point-prevalence study with haloperidol, the number of patients classified to be at risk for possibly harmful QT prolongation could be reduced by 50% using optimal QT rate correction.

CONCLUSIONS:

Fridericia and Framingham correction formulae showed the best rate correction and significantly improved prediction of 30-day and 1-year mortality. With current clinical standards, Bazett overestimated the number of patients with potential dangerous QTc prolongation, which could lead to unnecessary safety measurements as withholding the patient of first-choice medication.

KEYWORDS:

QT interval electrocardiography; electrocardiography; mortality; population; risk factors; risk prediction

PMID:
27317349
PMCID:
PMC4937268
DOI:
10.1161/JAHA.116.003264
[Indexed for MEDLINE]
Free PMC Article

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