The ECG data revealed a slight QT prolongation observed at two hours post hydroxyzine dose (at the time of peak plasma levels); however, the QTc analysis did not reveal an increased risk for clinically significant individual abnormalities. No clear treatment effect was seen on other ECG parameters. …show more content…
The most commonly used is the Bazett formula while the others are Fridericia, and Framingham formulas. While Bazett and Fridericia are logarithmic corrections, Framingham is linear correction formulae. In detail, Bazett’s formula: QT / (RR) 0.5 [Observed QT interval divided by root of RR interval, in seconds]; Fridericia’s formula: QT / (RR)0.33 [Observed QT interval divided by cube root of RR interval, in seconds] and Framingham formula: QT + 0.154 (1 – RR).
Bazett and Fridericia formulas were described long back and the initial studies involved only a very small number of patients of around 30 while Framingham formula was backed by a study of around 5000 patients. But Framingham formula is cumbersome to used at bedside being a linear regression equation
After studying over ten thousand ECGs, Luo and colleagues in 2004 opined that upper normal limits of corrected QT interval (excluding the top two percent) should be 460 millisecond for Fridericia’s formula. The values recommended for Bazett formula was 483 milliseconds while 457 milliseconds was suggested for Framingham