1513 - Amiodarone-Induced Severely Long QT Syndrome: A Case in a High-Risk Patient

Amiodarone-induced severe long QT syndrome

Case Description:

We present this case of a 66-year-old female with a past medical history of type 2 diabetes mellitus, hypertension, hyperlipidemia, atrial fibrillation, and recent left basal ganglia ischemic infarct who presented to our clinic for a post hospital follow-up visit. She was recently discharged after completing her post-stroke rehabilitation at Mountain View Rehabilitation Hospital. Her inpatient stay was complicated by Afib with rapid ventricular response and amiodarone was initiated. 

At our outpatient follow-up visit, an electrocardiogram (ECG) revealed a normal sinus rhythm with a prolonged corrected QT (QTc) interval of 584ms. Amiodarone was discontinued and the patient was resumed on prior metoprolol for rate control. One week later, a repeat ECG demonstrated a normalized QTc interval of 413ms.

Discussions: Amiodarone is a class III antiarrhythmic agent that inhibits outward potassium channels, and also exhibits class I, II, and IV antiarrhythmic activity. Severe acquired long QT syndrome (ALQTS), defined as a QTc interval ≥500ms increases the risk of polymorphic ventricular tachycardia, which can progress to torsades de pointes (TdP), a fatal arrhythmia. A retrospective review of 41,649 hospital admissions over six months suggests that 0.7% of patients had a QTc >500ms with female sex being the highest risk factor for drug induced-TdP. Patients with severe ALQTS are associated with increased all-cause mortality and frequency for syncope and life-threatening arrhythmia.

 Prior studies have also shown that upon discontinuation of amiodarone, QTc often normalizes within 1-5 days. We encourage clinicians to routinely review their patient medication lists and risk factors to maximize patient safety, especially in the setting of transitioning care. 


Conclusions: While amiodarone is an effective antiarrhythmic agent, it poses a significant risk for ALQTS and subsequent fatal ventricular arrhythmias. Intermittent ECG and electrolyte monitoring are essential to reduce the risk of life-threatening cardiac events.