An electrocardiographic series of flecainide toxicity

Anti-arrhythmic drugs (AADs) uniquely affect the various electrolyte channels in the heart and can slow conduction, increase refractoriness, and/or decrease automaticity with the goal of preventing tachyarrhythmias. Due to these properties, these same drugs are by nature pro-arrhythmic. Vaughan-Williams classification Ic AADs belong to a class of medications that inhibit sodium channels, leading to decreased conduction velocity of myocytes and Purkinje fibers as well as to decreased automaticity of pacemaker cells. When present in toxic amounts, this leads to classic changes on the electrocardiogram (ECG) that are harbingers of potentially lethal arrhythmias. Presented is a clinical series of ECGs that occurred in a patient who presented with flecainide toxicity.