Walter Lee, MD, Nikul Patel, MD, Jacquelynn Tran, BS, William Whitehead, MD ... Kay GN, Plumb VJ, Arciniegas JG, Henthorn RW, Waldo AL. Torsade de ...
Amiodarone Induced Torsades de Pointes Walter Lee, MD, Nikul Patel, MD, Jacquelynn Tran, BS, William Whitehead, MD Department of Anesthesiology University of Texas Medical Branch, Galveston, TX
Introduction Atrial fibrillation (AF) occurs postoperatively in 15-40% of patients after CABG and is associated with increased risk of heart failure, stroke, length of stay, and mortality. Amiodarone is an antiarrhythmic shown to be able to prevent post-op AF effectively but has potential to cause arrhythmias including Torsades de Pointes (TdP). TdP is a form of polymorphic ventricular tachycardia associated with prolonged QT interval and characteristic “twisting” of QRS peaks around an isoelectric line. It may lead to ventricular fibrillation and sudden death. The prolonged QT interval (defined as >460 ms in women) associated with TdP may be congenital or acquired. Drugs and electrolyte imbalances are two common causes of acquired long QT and TdP. Major drug classes that may cause prolonged QT include antiarrhythmics, macrolides, some antihistamines and psychotropic medications. These drugs affect QT during phase 3 of the action potential by blocking IKr K+ channels.
Case Report Continued… ACLS was performed and the patient was defibrillated twice and given 1 mg of epinephrine along with chest compressions with return of spontaneous circulation and a rhythm of sinus tachycardia. Prior to the event, patient was in sinus tachycardia with HR 100-110 and MAP 70-80. Potassium was 5.2 mEq/L, magnesium was 2.2 mEq/L, and ionized calcium was 4.60 mg/dL. Electrolytes were closely monitored and corrected appropriately. EKG later revealed sinus tachycardia and was notable for prolonged QTc of 507. The patient’s medication regimen was examined for drugs that could potentially prolong QT interval, and amiodarone was discontinued. She was later started on metoprolol and did not develop subsequent ventricular arrhythmias. The patient made a full recovery from the event and the surgery. She was eventually discharged and remained in sinus rhythm. Subsequent follow-up EKG’s at different hospital visits showed QTc ranging from 430-465.
EKG tracing Case Report
Discussion Post-op AF prophylaxis can be given with beta-blockers, amiodarone, or sotalol. Betablockers are the most well-studied for post-op AF and are ideally started for at least 48 hours before surgery due to concern of induction of excessive bradycardia. This patient presented within this window however, and amiodarone was initially selected as an alternative drug. After the patient recovered from the ventricular arrhythmias, she was able to tolerate beta-blocker without any notable adverse events. Amiodarone is a Class III antiarrhythmic (with additional effects similar to Class Ia, II, and IV) which predominantly blocks K+ channels and prolongs repolarization. Incidence of TdP associated with amiodarone is thought to be
