Deepak Saluja1, Jason A Guyotte2, James A Reiffel1. 1. Columbia University, College of Physicians and Surgeons, New York, NY. 2. Emory University School of Medicine, Atlanta, GA.
Abstract
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.
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.
Authors: Charlotte E Larroude; Berit T Jensen; Erik Agner; Egon Toft; Christian Torp-Pedersen; Kristian Wachtell; Jørgen K Kanters Journal: Heart Rhythm Date: 2006-06 Impact factor: 6.343