Abstract 12718: Better Than Bazett: Accounting for Recent Heart Rate History Improves QT Correction in Atrial Fibrillation
Introduction: QT interval prolongation is associated with a risk of polymorphic ventricular tachycardia. The QT interval shortens with increasing heart rate and correction for this effect is necessary for meaningful QT interval assessment. The best way to correct the QT interval during atrial fibrillation (AF) is uncertain.
Methods: Digitized Holter recordings were analyzed from patients with AF. Models of QT interval dependence on RR intervals were tested by sorting the beats into 20 bins based on corrected RR interval and assessing ST-T variability within the bins. Less variability indicated better model performance. Signal-averaging within bins was then performed to determine QT/RR dependence. Finally, standard deviation of QTc estimates was calculated for each model as a measure of real world utility.
Results: Data from 30 patients (29 men, 69.3±7.3 years) were evaluated. QT behavior in AF is well described by a linear function (slope ~0.19) of steady-state corrected RR interval, which combines an “immediate response” component (weight ~ 0.18) with an exponential weight function (time-constant 120 s) over the preceding 3 minutes. This model performs significantly (p<0.0001) better than models based on instantaneous RR interval only, provides better QT/RRc correlation, and results in more consistent QTc estimates. It also outperforms models based on shorter time-constants and other previously proposed models on all parameters.
Conclusions: QT interval accommodation during AF is well described by a formula combining a small “immediate response” to instantaneous RR interval change and an exponentially weighted “history” of RR intervals over the preceding 3 minutes. This model may improve detection of repolarization delay in AF. QT response to heart rate changes in AF is similar to previously published QT dynamics during atrial pacing and in sinus rhythm.
Author Disclosures: F.S. Riad: None. E. Razak: None. S. Saba: None. A. Shalaby: None. J. Nemec: None.
- © 2016 by American Heart Association, Inc.