Gender-specific comparison of six QT correction formulae in dyslipidemic patients in primary prevention

Aim: Analysis of QT duration limited to a single heart rate (HR) correction formula might be problematic in cross-sectional studies. Aim of this study was to investigate six frequently used equations with respect to over-and under-correction of QT intervals in a middle-aged population in primary prevention. Methods: A total of 404 individuals, 183 males (55.3±11.9y) and 222 females (64.3±9.6y) were investigated. HRs and QT intervals were measured automatically from resting ECGs. Six methods (Bazett, Fridericia, Hodges, Nomogram-Karjalainen, Rautaharju and Sagie-Framingham,) were used to correct the QT interval for HR. Exclusion criteria were: cardiovascular disease, left or right bundle branch block, atrial fibrillation and use of medications affecting QT interval duration (eg, beta-blockers, digoxin, anti-arrhythmics). Results: Males had shorter HR than females (63.3+/-8.9 vs. 67.8+/-10.0 beats/ min, p< 0.001), with shorter QTc Bazett (409.8+/-21.1 vs 425.5+/-21.9), Fridericia (406.7+/-20.0 vs. 417.5+/-20.8) Hodges (407.2+/-20.7 vs. 416.5+/-20.6), Nomogram-Karjalainen (408.1+/-20.0 vs. 418.8+/-20.3), Rautaharju (408.5+/-19.7 vs. 420.6+/-20.0) and Sagie-Framingham (406.5+/-19.7 vs. 417.9+/-20.1). Significant differences were observed between the genders for the QTc regardless of the formulas (p< 0.001). The Bazett formula performed worst (slopes B=0.7719 in males and 0.6662 in females); the Rautaharju best in terms of rate adjustment success in both males and females (slope B= 0.0366; 0.0534). Conclusions: These results demonstrate that automatic QT measurements performed can be used reliably in cardiovascular prevention, encouraging further investigation of their clinical value in risk stratification. The selected QT correction formulas apply to a specific population in particular in dyslipidemic patients.