estimate for QT based on heart rate in milliseconds =
= 496 - (1.75 * (heart rate))
corrected QT interval (QTm) =
= (QT interval) + (1.75 * ((heart rate) - 60))
Advantages:
(1) reduced variance in the correction
(2) absence of systematic error
(3) more accurate prediction of risk for ventricular arrhythmias
Disadvantages:
(1) prolongation of corrected QT interval during peak exercise
(2) overcorrects at high heart rates
Alternative representation (Luo et al):
corrected QT in milliseconds =
= (QT interval) + (105 * ((1/(RR interval in seconds)) - 1))
where:
• R-R interval is the measurement between 2 consecutive R-R waves in seconds.
• RR = 60 / (heart rate) in a simplified world
• 105 = 1.75 * 60
As noted by Luo et al (in the abstract), QT shows a linear trend with heart rate but not with the RR-interval.
