A method differentiating LQT1 mutation from LQT2 mutation is disclosed. An ECG signal is obtained for a patient. At least a first ECG parameter and a second ECG parameter are determined from the ECG signal. A probability that the patient is an LQT1 carrier or an LQT2 carrier is determined based on a regression model which takes into account the first ECG parameter and the second ECG parameter. A system for assessing repolarization abnormalities is also disclosed. The system has a processor configured to differentiate between LQT1 and LQT2 based on at least two ECG parameters from ECG data. The system also has a data input coupled to the processor and configured to provide the processor with the ECG data. The system further has a user interface coupled to either the processor or the data input.