Evaluation of repolarization dynamics using the QT–RR regression line slope and intercept relationship during 24-h Holter ECG

QT–RR linear regression consists of two parameters, slope and intercept, and the aim of this study was to evaluate repolarization dynamics using the QT–RR linear regression slope and intercept relationship during 24-h Holter ECG. This study included 466 healthy subjects (54.6 ± 14.6 years; 200 men and 266 women) and 17 patients with ventricular arrhythmias, consisted of 10 patients with idiopathic ventricular fibrillation (IVF) and 7 patients with torsades de pointes (TDP). QT and RR intervals were measured from ECG waves based on a 15-s averaged ECG during 24-h Holter recording using an automatic QT analyzing system. The QT interval dependence on the RR interval was analyzed using a linear regression line for each subject ([QT] = A[RR] + B; where A is the slope and B is the y-intercept). The slope of the QT–RR regression line in healthy subjects was significantly greater in women than in men (0.185 ± 0.036 vs. 0.161 ± 0.033, p < 0.001) and the intercept was significantly smaller in women than in men (0.229 ± 0.028 vs. 0.240 ± 0.027, p < 0.001). A scatter diagram of the QT–RR regression line slope and intercept among healthy subjects demonstrated a statistically significant negative correlation (B = −0.62A + 0.34, r = −0.79). Distribution of both scatter diagrams of the slope and the intercept of the QT–RR regression line in patients with IVF and TDP was different from healthy subjects (left corner for IVF and upward shift for TDP). The slope and intercept relationship of the QT–RR linear regression line based on 24-h Holter ECG may become a simple useful marker for abnormality of ventricular repolarization dynamics.