Snapshot A 15-year-old girl presents with palpitations and dizziness. She has had similar episodes in the past but has never needed to go to a hospital. Her family history includes sudden cardiac death in her father and congenital sensorineural deafness in multiple family members. An echocardiogram reveals a sinusoidal waveform concerning for torsades de pointes. (Jervell and Lange-Nielsen syndrome) Introduction Clinical definition a polymorphic ventricular tachycardia characterized by sinusoidal and cyclic alterations on electrocardiogram (ECG) Epidemiology demographics female > male women have longer QT intervals risk factors hypomagnesemia hypokalemia 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 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 the triggered activity can produce torsades de pointes in susceptible patients Associated conditions congenital long QT syndrome Jervell and Lange-Nielsen syndrome autosomal recessive congenital sensorineural deafness Romano-Ward syndrome autosomal dominant no sensorineural deafness Prognosis usually preceded by a period of long QT intervals typically resolves spontaneously, but may degenerate into ventricular fibrillation and death 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 a sinusoidal waveform Making the diagnosis based on clinical presentation and electrocardiogram Differential Supraventricular tachycardia distinguishing factor non-sinusoidal waveforms on electrocardiogram Treatment Conservative discontinue all QT prolonging drugs indication for all patients outcomes torsades de pointes due to drugs typically do not recur after withdrawal of the drug Medical magnesium sulfate indications for all patients mechanism of action suppresses early afterdepolarizations to terminate the arrhythmia magnesium decreases influx of calcium and lowers the amplitude of the early afterdepolarizations β-antagonists indications long-term therapy for patients with congenital long QT syndrome only for those without bradycardia drugs propranolol esmolol Operative pacing indication long-term therapy for patients who are symptomatic despite pharmacologic treatment typically for patients with congenital long QT syndrome Complications Ventricular fibrillation