Statistical analysis
Measurements are presented as mean value ± SD. Comparisons of measurements between two groups were analyzed by Mann–Whitney U test. Fisher exact test was used for discrete variables. Receiver-operator characteristics (ROC) curves were used to optimize each parameter’s cutoff value for differentiation between LQT1 and LQT2.
A p-value < .05 was considered significant. Statistical calculations were performed with SPSS version 20 software (IBM Inc., Chicago, Illinois, USA).