Assessment of QT Interval in Ventricular Conduction Defects: Validation of a New Formula

• Published in: Journal of electrocardiology 2018-11, Vol.51 (6), p.1184-1184
• Main Author: Gil, Miguel Ángel Cobos
• Format: Article
• Language: English
• Subjects: Cardiac arrhythmia; Data analysis; Electrocardiography; Patients
• ISSN: 0022-0736; 1532-8430
• DOI: 10.1016/j.jelectrocard.2018.10.081

Background: QT interval prolongation is a marker of abnormal repolarization. In patients with major ventricular conduction defects (VCD), the assessment of ventricular repolarization remains controversial. Use of special indexes, or 2-parameters formulas for QTc and JTc has been proposed. However, the complexity of these methods precludes its wide clinical application. We have proposed (AHA 2012) a very simple formula for QT correction: QTc=2QT/((l +RR)). We propose that this expression can be used for the evaluation of repolarization across all the spectrum of QRS duration (QRSD), including patients with ventricular conduction defects. Methods: We have analyzed the data from a random subset (19023 subjects, including 434 VCD cases) of the ECC-ViEW II, a Korean electrocardiogram database. We calculated the QTc interval using 4 correction formulas (Bazett, Fridericia, Framinham, and our new formula). We correlated the QTc values of each method with the RR interval and QRS duration (QRSD), performing a multiple regression analysis . An ideal correction formula should minimize the coefficient of determination (R2). Results: We found that our formula provides the best correction. (R2 for the new formula 0, 07, Bazett 0,16, Fridericia 0,22, Framinham 0,12). Using the new formula in the subjects with normal ventricular conduction, the mean QTc is 0,416 +- 0,023 with an upper 5% normal limit of 0,459. In the VCD cases these values are 30 ms higher (mean 0,446 +- 0,028, upper 5% normal limit 0,489) Conclusion: We propose a very simple, universal formula for the evaluation of QT interval in patients with normal conduction and in patients with major ventricular conduction defects.