Conventional QT corrections may be inappropriate in AF due to RR variability and
QT lag. Existing formulas have been modified by RRmod to account for this lag. We
developed a novel correction formula for use in AF (QTAF) based on the slope
∆QT/∆RRmod and report its performance in AF. We also compare QTAF obtained in AF with
rate-independent corrections in NSR.
A total of 3063 RR/QT pairs from
28 patients with AF were measured, 22 of whom also had measurements during sinus
rhythm. QTc, QTLC, and QTAF were calculated
utilizing RRmod, and the rate-independence of each formula in AF
tested. Mean QTAF values in AF were compared to QT intervals
corrected with QTLC in NSR.
∆QTc/∆RRmod and ∆QTLC/∆RRmod slopes were significantly non-zero
whereas ∆QTAF/∆RRmod was not. QTLC and QTc corrections were imperfect at extremes of RRmod while QTAF was constant. QTAF corrections in AF were shorter than QTc or QTLC corrections in NSR.
QTAF is a novel QT correction
with a defined relationship to correction in NSR that performs better than
Credits: Deepak Saluja; Jason A. Guyotte; James A.Reiffel