- Patient is unstable. Shock instead.
- Patient is pregnant. Amiodarone is class D. Consider lidocaine (class B - no evidence of risk to humans) or procainamide (class C - risk can't be ruled out) instead.
- Patient is in atrial fibrillation with WPW. Amiodarone has AV nodal blocking properties which encourages conduction down the accessory pathway and may induce ventricular tachycardia/fibrillation. Consider procainamide or shock instead.
- Torsades. Amiodarone will prolong the QT interval making things worse. Consider magnesium instead.
- Accelerated idioventricular rhythm. AKA "slow VT." This rhythm arises below the AV node and has a rate between 50 - 120 beats/min. It can be an escape rhythm or represent an abnormal ectopic focus in the ventricle that competes with the sinus node. Pharmacologic treatment is CONTRAINDICATED if AIVR is an escape rhythm (as it often is in setting of myocardial infarction), since supression of the pacemaker focus can result in asystole. There is no convincing data linking AIVR to sustained VT or VF.
Mattu, A. MD. EM Cast: Amiodarone Imperfections. Dec 2008. http://www.emedhome.com
Podrid, P. MD. "Ventricular arrhythmias in heart failure and cardiomyopathy" Up to Date. Oct 2008.