Adverse reactions to antiarrhythmic drugs

Abstract

There are various types of adverse reactions to antiarrhythmic drugs (AADs). Proarrhythmia, which refers to an exacerbation of the preexisting arrhythmia or occurrence of a new arrhythmia, may occur under the therapeutic concentration of an AAD. Bradyarrhythmia is the most common type of proarrhythmia due to AADs, and prior myocardial infarction and old age are known risk factors. Atrial flutter with 1:1 atrioventricular conduction usually occurs during rhythm control of atrial fibrillation with class IC AADs. QT prolongation due to AADs, mainly class III AADs, elevates the risk of torsade de pointes by triggered activity due to early afterdepolarization. The addition of clinical factors that promote QT prolongation, such as hypokalemia, hypomagnesemia, female sex, and bradycardia, increases the risk of developing torsade de pointes. Proarrhythmic monomorphic ventricular tachycardia usually occurs as a result of slow conduction and disparity of refractoriness due to class IC AADs. In patients with preexisting left ventricular systolic dysfunction or structural heart disease, the risk of hypotension or cardiogenic shock caused by negative inotropic effects due to AADs should be considered. To prevent these major adverse reactions to AADs, we need to understand the electrophysiologic properties of AADs in detail. Furthermore, the risk of proarrhythmia could be heightened by interplay with clinical factors, such as electrolyte unbalances, heart rate, and hepatic/renal or myocardial dysfunction. Sufficient awareness about drug-drug interactions, which may affect the metabolism of AADs, will improve patient safety during the management of arrhythmia.