Dilemma of finding the most useful QTc formula: a retrospective analysis of south-east London

Abstract

Background: Accurate measurement of the corrected QT (QTc) interval is crucial for assessing the risk of arrhythmias. Various formulas, including Bazett’s, Fridericia’s, Framingham’s, and Hodges’, are used to calculate QTc, but discrepancies between them can lead to clinical misclassification. Objectives: This study aimed to compare the performance of different QTc formulas and identify the most reliable method for clinical practice. Methods: A retrospective analysis was conducted on 200 type 2 diabetic patients from South-East London. QT and RR intervals were measured to calculate QTc values. Due to the non-normal distribution of QTc values (Shapiro-Wilk test, p < 0.05), non-parametric statistical methods were employed, including the Friedman test and pairwise Wilcoxon signed-rank tests, to assess differences between QTc formulas. Results: The mean QTc values differed significantly between formulas, with Bazett’s formula producing higher values (445 ± 30 ms) compared to Fridericia’s (426 ± 29 ms), Framingham’s (424 ± 28 ms), and Hodges’ (428 ± 29 ms) formulas. The Friedman test confirmed significant variation across formulas (χ²(3) = 218.86, p < 0.001). Fridericia’s formula demonstrated consistent performance and lower variability compared to other formulas. Conclusion: This study highlights the importance of selecting an appropriate QTc correction formula. Fridericia’s formula may be a more reliable choice for accurate QTc interval measurement in clinical practice, particularly in patients with varying heart rates.