Torsades de Pointes

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Pause-dependent polymorphic ventricular tachycardia occurs in the presence of a prolonged QT interval (ECG pattern often resembles twisting around a point, hence the name)

• Torsades de pointes in congenital long QT syndrome (LQTS) is not pause dependent:

  • – It is referred to as adrenergic torsades de pointes

  • – It is secondary to delayed after depolarizations (DADs) due to prolonged refractory period of the cardiac action potential

GENERAL CONSIDERATIONS

• Lengthening of the pause-dependent action potential provides the substrate for the arrhythmia

• QT prolongation may be induced by:

  • – Medications such as class IA and III antiarrhythmic drugs

  • – Antibiotics such as erythromycin (macrolides), fluoroquinolones

  • – The phenothiazine group of drugs

  • – Metabolic states such as hypokalemia and hypomagnesemia

• Antihistamines such as terfenadine can cause QT prolongation (avoid in combination with macrolide antibiotic)

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Family history of LQTS in some

• Malignant syncope

• Lightheadedness

• Palpitations

• Sudden cardiac death

PHYSICAL EXAM FINDINGS

• Deafness as part of congenital LQTS

DIFFERENTIAL DIAGNOSIS

• Polymorphic ventricular tachycardia secondary to acute ischemia (QT interval may be normal)

• Catecholamine-dependent polymorphic ventricular arrhythmia

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• Serum potassium

• Serum magnesium

• Cardiac biomarkers

• Basic metabolic panel

ELECTROCARDIOGRAPHY

• ECG usually shows prolonged QT interval

• Telemetry for arrhythmia detection

• Outpatient cardiac monitoring if patient complains of palpitations or syncope but has no documented arrhythmia

IMAGING STUDIES

• Echocardiogram to evaluate left ventricular function and evaluate for structural heart disease

TREATMENT

CARDIOLOGY REFERRAL

• All patients should be evaluated by a cardiologist and preferably by an electrophysiologist at the cardiologist’s discretion

HOSPITALIZATION CRITERIA

• All patients must remain hospitalized until the problem resolves and secondary prevention is addressed

MEDICATIONS

• Patients with hemodynamic collapse require emergent electrical countershock

• Stable patients can start with aggressive boluses of IV magnesium

• For frequent pauses, consider temporary pacing (ideally atrial pacing) or IV isoproterenol

• Eliminate medications that prolong the QT interval

• Beta blockers for congenital LQTS

THERAPEUTIC PROCEDURES

• Implantable cardioverter-defibrillator (ICD) in patients with congenital LQTS

MONITORING

• ECG monitoring in the hospital

DIET AND ACTIVITY

• No long-term restrictions recommended

ONGOING MANAGEMENT

HOSPITAL DISCHARGE CRITERIA

• Once the acute symptoms and arrhythmia resolve

• After an ICD implantation in patients with ...