The present invention relates to a system or method for analyzing drug influence on ECG curvature and Long QT Syndrome. The system has an input means connected to an ECG source, where different parameters of a received ECG curvature are indicated and/or isolated for indicating possible symptoms which relate to certain diseases that influence the ECG curvature. The aim of the invention is to achieve a system and a method for diagnosing Long QT Syndrome in an objective, fast and effect way by indication of a number of symptoms derivable from an ECG curve. Further aim is to achieve an effective test of drug influence on ECG curvature. The system analyzes the QT curvature of the ECG curvature for indicating Long QT Syndrome.