TQTc stands for 'thorough QT/QTc study'. The test studies the effect of a compound on the electrical activity of the heart. In cardiology, the QT interval is a measure of the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle. The QT interval represents the electrical activity associated with the contraction and relaxation of the heart chambers. A lengthened QT interval is used as an (imperfect) biomarker to assess the risk that a medicine may provoke arrhythmia.