Drugs acting on the heart: antiarrhythmics

Arrhythmias are abnormalities of cardiac rate or rhythm occurring for a variety of reasons. They are common in the perioperative period and in intensive care. Causes may reflect an underlying heritable predisposition, the presence of new pathology either of the heart or conducting system, or as a result of systemic illness. Targets for antiarrhythmics include myocardial ion channels, muscarinic or nicotinic acetylcholine receptors, adrenergic or adenosine receptors. Arrhythmias may cause cardiac arrest and haemodynamic compromise, requiring rapid identification and corrective treatment either of rate or rhythm. Even where stable, arrhythmias present an increased risk of thromboembolic events requiring the use of anticoagulation. Treatment may be directed at controlling heart rate or rhythm to restore the circulation and tissue perfusion. Strategies may include prevention or correction of precipitating factors (such as electrolyte abnormalities or sepsis) and sometimes non-pharmacological treatments (cardioversion, surgical ablation or pacing). Antiarrhythmic drugs are often required. The targets, mechanisms and clinical guidelines are reviewed for common antiarrhythmic agents.