What is the diagnosis and treatment for Torsades de Pointes (TdP), a type of abnormal heart rhythm characterized by a specific pattern on an electrocardiogram (ECG)?

From the Guidelines

Torsades de pointes should be managed with immediate administration of IV magnesium sulfate 2g over 1-2 minutes as first-line therapy, regardless of serum magnesium levels, as recommended by the 2017 AHA/ACC/HRS guideline 1. The management of torsades de pointes involves several key steps, including:

• Stopping any QT-prolonging medications
• Correcting electrolyte abnormalities, particularly potassium and magnesium
• Administering IV magnesium sulfate 2g over 1-2 minutes as first-line therapy, regardless of serum magnesium levels
• Considering electrical cardioversion at 120-200 joules (biphasic) for unstable patients with persistent torsades
• Using isoproterenol infusion (2-10 mcg/min) or temporary overdrive pacing to increase heart rate and shorten the QT interval if torsades recurs or the patient remains unstable Some key points to consider in the management of torsades de pointes include:
• The importance of maintaining potassium levels >4.0 mEq/L and magnesium >2.0 mg/dL to prevent torsades
• The need to avoid class IA and III antiarrhythmics, which can worsen QT prolongation
• The use of temporary pacing to manage torsades de pointes that is recurrent after potassium and magnesium supplementation, as recommended by the 2017 AHA/ACC/HRS guideline 1
• The effectiveness of intravenous magnesium in suppressing episodes of torsades de pointes without necessarily shortening QT, even when serum magnesium is normal, as noted in the 2017 AHA/ACC/HRS guideline 1.

From the Research

Torsades de Pointes Overview

• Torsades de pointes is a life-threatening ventricular tachycardia that occurs in the setting of a prolonged QT interval 2.
• It is most frequently related to administration of antiarrhythmic drugs, but can also be caused by other factors such as low serum electrolyte levels, organic heart disease, and bradycardia or baseline QT prolongation 2.

Recognition and Diagnosis

• Prompt recognition of torsades de pointes is imperative, and the clue to its recognition is increased awareness 3.
• The QT interval in the long QT syndrome (LQTS) is not only prolonged but also odd looking, with abnormal QT morphology and giant U waves 3.
• The onset of ventricular extrasystoles and the appearance of bizarre QT changes in the sinus complex that follows each postextrasystolic pause are signs of "impending torsades" 3.

Treatment Options

• Emergency treatment includes withdrawal of any precipitating agents, intravenous administration of magnesium sulfate, potassium supplements, and lidocaine, and adequate sedation 3.
• For drug-refractory torsades de pointes, transvenous ventricular pacing at rapid rates can shorten the QT interval, eliminate the pauses that precipitate torsades, and prevent further bursts of arrhythmias 3.
• Acceleration of the basic heart rate with isoproterenol is also effective in preventing immediate recurrence, but should only be used in specific cases 3.
• Magnesium sulfate is a safe and effective treatment for torsades de pointes, and can be administered intravenously with a bolus dose followed by continuous infusion 4, 2, 5.
• The optimal dosage and serum magnesium concentration for torsades de pointes treatment are 3 to 12 mg/kg, 0.5 to 1.0 mg/kg/hr, and 3 to 5 mg/dL, respectively 4.

Prevention

• Torsades de pointes can be prevented by avoiding agents known to induce arrhythmias in patients with a pre-existing prolonged QT interval 6.
• Periodic serum electrolyte assessment is warranted, and new drugs that prolong the QT interval should be considered potential causative agents of torsades de pointes 6.