Drug-induced torsade de pointes.

Area of Science:

• Cardiology
• Clinical Pharmacology
• Electrophysiology

Background:

• Torsade de pointes (TdP) is a specific form of ventricular tachycardia characterized by a prolonged QT interval and polymorphic QRS complexes.
• Drug-induced TdP can arise from therapeutic doses of medications affecting cardiac repolarization, including certain antiarrhythmics and psychotropics.
• Identifying predisposing factors and understanding clinical presentations are crucial for managing this potentially life-threatening arrhythmia.

Observation:

• Three cases illustrate TdP associated with thioridazine, trifluoperazine, quinidine, and procainamide.
• Clinical scenarios included syncopal episodes, ventricular tachycardia progressing to ventricular fibrillation, and refractory ventricular arrhythmias.
• Electrocardiographic findings consistently showed polymorphous ventricular tachycardia and a prolonged QT interval.

Findings:

• Drug-induced TdP management involves definitive emergency therapy with overdrive pacing and supportive care with electrolyte repletion (potassium and magnesium).
• Lidocaine and bretylium are generally ineffective for TdP, while isoproterenol may be cautiously used.
• Prevention strategies emphasize avoiding known QT-prolonging agents in susceptible patients and monitoring serum electrolytes.

Implications:

• Clinicians must be vigilant for TdP in patients prescribed drugs known to prolong the QT interval.
• Proactive patient assessment for pre-existing conditions (e.g., prolonged QT syndrome) and regular electrolyte monitoring are essential.
• Understanding the specific mechanisms and management of TdP is critical for improving patient outcomes and preventing sudden cardiac death.