Key result
The novel QTAF formula provided a rate-independent QT correction in atrial fibrillation (slope -0.003, p>0.05), outperforming conventional QTc and QTLC formulas which remained significantly rate-dependent.
Why the study?
Does the novel QTAF formula improve rate-independent QT correction compared to QTc and QTLC in patients with atrial fibrillation?
Observational (n=28)
No
Does the novel QTAF formula improve rate-independent QT correction compared to QTc and QTLC in patients with atrial fibrillation?
Absolute Event Rate: -0.003% vs -0.081%
p-value: p=>0.05
The novel QTAF formula provides a more rate-independent QT correction in atrial fibrillation compared to conventional Bazett and Framingham formulas, which may improve the assessment of proarrhythmic risk.
May support QTAF for QT assessment in AF; leaves open prospective outcome validation before practice change.
BACKGROUND: Conventional QT corrections may be inappropriate inatrial fibrillation (AF) due to RR variability and QT lag. Existing formulashave been modified by the formula RRmod to account for this lag. Wedeveloped a novel correction formula for use in AF (QTAF) based onthe slope ∆QT/∆RRmod and report its performance in AF.We also compare QTAF obtained in AF with rate-independentcorrections in NSR. MATERIALS AND METHODS: A total of 3063 RR/QT pairs from 28 patients with AFwere measured, 22 of whom also had measurements during sinus rhythm. QTc (theBazett equation), QTLC (the Framingham linear correction), and QTAFwere calculated utilizing RRmod, and the rate-independence of eachformula in AF tested. Mean QTAF values in AF were compared to QTintervals corrected with QTLC in normal sinus rhythm. RESULTS: ∆QTc/∆RRmod and∆QTLC/∆RRmod slopes were significantlynon-zero whereas ∆QTAF/∆RRmod was not. QTLCand QTc corrections were imperfect at extremes of RRmod whileQTAF was constant. QTAF corrections in AF were shorterthan QTc or QTLC corrections in NSR. CONCLUSIONS: QTAF is a novel QT correction with adefined relationship to correction in NSR that performs better than existingstrategies.
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Saluja et al. (2008) conducted an observational in Atrial Fibrillation (n=28). QTAF formula vs. QTc (Bazett) and QTLC (Framingham) formulas was evaluated on Rate-independence of QT correction (ΔQTx/ΔRRmod slope) (p=>0.05). The novel QTAF formula provided a rate-independent QT correction in atrial fibrillation (slope -0.003, p>0.05), outperforming conventional QTc and QTLC formulas which remained significantly rate-dependent.
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