23-35: Polymorphic Ventricular Tachycardia

ECG Findings

• Wide-complex irregular, extreme tachycardia

• QRS complexes with changing morphology

Pearls

1. Polymorphic ventricular tachycardia (PVT) may occur in association with a normal QT interval or a prolonged QT interval. When associated with a prolonged QT interval, torsades de pointes is diagnosed.

2. Normal-QT PVT is typically associated with cardiac ischemia. Immediate treatment consists of cardioversion; ventricular antiarrhythmics such as amiodarone, procainamide, or lidocaine may be used followed by assessment for and treatment of ischemia.

3. Torsades de pointes (literally translated “twisting of the points” in French) has a characteristic “twisting” appears of the QRS complexes around the ECG baseline, as shown in Figs. 23.24A-B.

4. Immediate treatment for torsades de pointes consists of cardioversion; if cardioversion is unsuccessful, a bolus of intravenous magnesium should be given. If the arrhythmia persists, overdrive electrical pacing or overdrive chemical pacing (with isoproterenol) will help shorten the relative QT and convert the patient back to sinus rhythm. Following conversion, a magnesium infusion should be initiated, and the cause of the prolonged QT should be aggressively sought out and treated.