Cardiac safety, drug-induced QT prolongation and torsade de pointes (TdP)

摘要

Torquere is Latin for 'to twist' and gave rise to 'torque' in English and, in French, to 'torsade' a 'twisted fringe, cord or ribbon'. Torsade de pointes (TdP) is a ballet sequence in which the dancer twists around her'pointes' (dancing en pointe means'onthetip'and is a classical ballet technique, usually performed using special shoes called pointes). Des-sertenne used this phrase to describe a distinctive form of ventricular tachycardia in an elderly woman, because the electrical axis of the ventricular complexes varied cyclically giving the electrocardiogram (ECG) a twisted appearance (Figure 1) . Similar polymorphic ventricular tachycardia had previously been identified as the cause of loss of consciousness during quinidine therapy ('quinidine syncope') TdP can be fatal and occurs in several clinical settings associated with prolongation of the ventricular action potential, notably drug treatment and inherited abnormalities of cardiac ion channels. Prolongation of the ventricular action potential is recognized non-invasively by QT segment prolongation on the ECG (a useful but tricky surrogate end-point for risk of clinically important.