Which QT Correction Formulae to Use for QT Monitoring?

Abstract

BackgroundDrug 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 ResultsAll 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.ConclusionsFridericia 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.

Characteristics of cardiomyopathy in Alström syndrome: Prospective single-center data on 38 patients

“…This difference may be explained by the fact that we corrected the QT interval using both the Bazett and Fredericia formulas. The Fredericia formula has been proven to be superior to the Bazett formula, especiallyin terms of risk assessment for mortality [23]. In addition, in our cohort, we did not identify an increased incidence of arrhythmias or symptoms related to abnormal heart rhythms.…”

Impact of QTc formulae in the prevalence of short corrected QT interval and impact on probability and diagnosis of short QT syndrome

“…Vanderbecket al have shown that Fridericia and Framingham correction provide the best rate correction for prolonged QT intervals and improved prediction of 30-day and 1-day mortality 15. In the setting of short QTc intervals, the association of different formulae with a higher probability of arrhythmic events remains to be proven, and assessing which one of the linear regression functions ( Framingham , Hodges or others8) to use, should be the aim of future research.…”

A prolonged QTc‐interval at the emergency department: Should we always be prepared for the worst?

“…All adult patients (≥18 years) who had an ECG performed at the ED during a 3‐month period from 1 August, 2014 to 31 October, 2014, were eligible for inclusion in the study. QTc‐intervals >450 millisecond for men, and >470 millisecond for women were considered prolonged . The cutoffs were on the basis of the proposal by Goldenberg et al in 2006 and are supported by our previous work in a healthy subset determining an optimal reference interval for each formula .…”

“…In daily clinical practice, the Bazett correction formula (QTcB) is the most frequently used formula despite multiple reports of its limitations . There is a known overcorrection at high heart rates and a lack of correction for ventricular conduction defects (VCD) . This could lead to a large number of patients misclassified by automatic warning systems incorporating QTcB as having an increased risk and requiring more intensive medical follow‐up, whereas better correction formulas are available.…”