1. The electrophysiological mechanisms responsible for the long QT interval and torsades de pointes in patients with acquired and idiopathic LQTS are uncertain. 2. The intracardiac abnormality results in afterdepolarisations, probably early afterdepolarisations, that cause triggered activity and torsades de pointes. 3. EADs have been documented from the endocardium in a patient with quinidine-induced long QT interval and torsades de pointes. 4. The agents and clinical situations that cause torsades de pointes also prolong repolarisation. 5. Syncope is unrelated to plasma concentrations of quinidine or duration of therapy, and torsades de pointes can occur at low plasma concentrations. 6. Procainamide and disopyramide likewise have the potential for causing torsades de pointes. 7. Thioridazine prolongs the QT interval, produces T wave changes and occasionally torsades de pointes, and has been implicated as a cause of sudden death in schizophrenics. 8. Haloperidol has been implicated as a cause of torsades de pointes and death. 9. Hypokalaemia and hypomagnesaemia, when severe, can prolong repolarisation and precipitate torsades de pointes. 10. Liquid protein diets, and nutritional disorders such as starvation and anorexia nervosa, have likewise been associated with QT prolongation, torsades de pointes, and sudden death. |