Snapshot A 45-year-old woman presents to the emergency room for a syncopal episode. She currently experiences lightheadedness and palpitations. Her medications include ondansetron and oral contraceptives. An electrocardiogram reveals torsades de pointes. She is given magnesium sulfate. Introduction Clinical definition a polymorphic ventricular tachycardia characterized by sinusoidal and cyclic alterations on electrocardiogram (ECG) Associated conditions congenital long QT syndrome Jervell and Lange-Nielsen syndrome login to view 2 more bullets Romano-Ward syndrome login to view 2 more bullets Epidemiology Demographics female > male women have longer QT intervals Risk factors ↓ magnesium ↓ potassium Etiology Familial Drugs (ABCDE) class IA Antiarrhythmics (quinidine, procainamide, and disopyramide) due to ↑ QT interval class III Antiarrhythmics (sotalol and ibutilide) antiBiotics antipsyChotics antiDepressants antiEmetics diuertics (e.g., furosemide) Pathogenesis torsades de pointes is thought to result from prolonged repolarization and early afterdepolarizations when early afterdepolarizations reach the threshold potential and depolarize the cell membrane, triggered activity occurs, resulting in additional action potentials login to view 1 more bullet Presentation Symptoms palpitations dizziness syncope symptoms may be triggered by stress sudden cardiac death Physical exam tachycardia pallor Studies Labs serum electrolytes (↓ magnesium and potassium) Electrocardiogram (ECG) if in sinus rhythm prolonged QT interval pathological U waves if in an episode change in polarity of QRS around the isoelectric line sinusoidal waveform Differential Supraventricular tachycardia distinguishing factor non-sinusoidal waveforms on electrocardiogram Diagnosis Making the diagnosis based on clinical presentation and electrocardiogram Treatment Conservative discontinue all QT prolonging drugs indication login to view 1 more bullet outcomes login to view 1 more bullet Medical magnesium sulfate indications login to view 1 more bullet mechanism of action login to view 2 more bullets β-antagonists indications login to view 2 more bullets drugs login to view 2 more bullets Operative pacing indication login to view 2 more bullets Complications Ventricular fibrillation Prognosis Usually preceded by a period of long QT intervals Typically resolves spontaneously but may degenerate into ventricular fibrillation and death