Prolonged QT Syndrome, Torsades

Drugs

• Complete list at www.QTDrugs.org
• Class Ia antidysrhythmics—quinidine, procainamide, disopyramide
• Class III antidysrhythmics—sotalol, ibutilide, amiodarone
• Antibiotics—erythromycin, pentamidine, chloroquine, trimethoprim–sulfamethoxazole
• Antifungal agents—ketoconazole, itraconazole
• Psychotropic drugs—phenothiazines, haloperidol, risperidone, STCAs
• Cisapride
• Antihistamines
• Organophosphates
• Narcotics—methadone

Electrolyte abnormalities

• Hypokalemia
• Hypomagnesemia
• Hypocalcemia

Cardiac

• Bradyarrhythmias
• Arteriovenous block
• Mitral valve prolapse
• Myocarditis
• Myocardial ischemia

CNS

• Subarachnoid hemorrhage
• Stroke
• Congenital (idiopathic)

Other

• Protein-sparing fasting
• Anorexia nervosa
• Hypothyroidism
• Hypothermia

• Stable patients with prolonged QT transported without intervention
• Cardioversion for unstable patients with confirmed torsades de pointes
• Magnesium sulfate for stable patients with evidence of torsades de pointes

ED TREATMENT/PROCEDURES

• Magnesium sulfate followed by pacing for torsades de pointes.

  • Magnesium sulfate: 2 g (peds: 25–50 mg/kg) IV bolus over 2–3 min followed by IV infusion at 2–4 mg/min

• Potassium to serum levels of 4.5–5 mEq/L
• Temporary transvenous cardiac pacing (rates from 100–120 beats/min) for recurrences of torsades de pointes refractory to magnesium sulfate therapy (shortens QTc)
• IV isoproterenol for refractory cases or hemodynamically unstable patients with acquired long QT (ineffective in congenital cases) who do not respond to transvenous pacing

  • • Isoproterenol: 1 μg/min (peds: 0.05–0.1 μg/kg/ min) IV continuous infusion, titrate for effect, up to 10 μg/min

• Remove any offending medications and correct metabolic derangements.
• Consult with cardiology in those with symptomatic long QT regarding use of β-blockers at maximum doses.
  
  • Propranolol: 2–3 mg/kg/d (peds: 2–3 mg/kg/d) PO (in consultation with cardiology)
• Pacemaker or defibrillator placement with or without cervicothoracic stellectomy (to reduce adrenergic stimulation) may be required in high-risk patients.
• β-Blockers prevent 70% of cardiac events in congenital cases.

▢ EKG ordered, look for prolonged QT syndrome
▢ Recognition of torsades after decompensation
▢ Resuscitation per pediatric advanced life support (PALS) guidelines
▢ Cardiology consultation