Results
The QTe/RR and QTa/RR slopes at the entire 24-hour were significantly steeper in LQT2 compared to those in LQT1 patients (0.262 +/- 0.063 vs 0.204 +/- 0.055, P = 0.0007; 0.233 +/- 0.052 vs 0.181 +/- 0.040, P = 0.0002, respectively). The QTe interval was significantly longer, QTe/RR and QTa/RR slopes at daytime were significantly steeper in LQT2 than in LQT1 patients. The receiver operating curve analysis revealed that the QTa/RR slope of 0.211 at the entire 24-hour Holter was the best cut-off value for differential diagnosis between LQT1 and LQT2 (sensitivity: 80.0%, specificity: 75.0% and area under curve: 0.804 [95%CI = 0.68-0.93]).