Chapter 22: Arrhythmias – Antiarrhythmic Drug Therapy

Arrhythmias are clinically categorized as supraventricular (e.g., Atrial Fibrillation/Flutter, PSVT) or ventricular (e.g., VT, VF), with the latter typically requiring more urgent intervention. Patient management focuses first on correcting reversible causes (like electrolyte imbalances or drug toxicity) and assessing hemodynamic stability. Antiarrhythmic Drugs (AADs) are categorized using the Vaughan Williams system: Class I (Sodium channel blockers: Ia, Ib, Ic), Class II (Beta-blockers), Class III (Potassium channel blockers), and Class IV (Nondihydropyridine Calcium Channel Blockers). Specific agents are examined, noting their mechanism, pharmacokinetics, and adverse effects; for instance, Class Ia drugs like quinidine can cause TdP and have anticholinergic effects, while Class Ib agents like lidocaine are effective primarily for ventricular arrhythmias in ischemic tissue. Class III agents, such as amiodarone and sotalol, significantly prolong the QT interval, with amiodarone being unique for its multi-class properties and relative safety in heart failure with reduced ejection fraction (HFrEF), despite risks like pulmonary toxicity. Treatment strategies for persistent or recurrent Atrial Fibrillation emphasize ventricular rate control (using agents like beta-blockers, diltiazem, or digoxin based on LV function) and meticulous anticoagulation based on the CHA2DS2-VASc score, often preferred over rhythm control due to clinical trial data. Pharmacological or electrical cardioversion is used to restore sinus rhythm, requiring careful consideration of the duration of AF and necessary anticoagulation measures to prevent thromboembolism. Acute, life-threatening arrhythmias like Pulseless VT/VF require immediate high-quality cardiopulmonary resuscitation (CPR), defibrillation, and administration of vasopressors (epinephrine), followed by AADs like amiodarone or lidocaine. Special populations, such as geriatric patients, require dosage adjustments due to declining organ function, and comprehensive patient education regarding medication adherence, monitoring for adverse effects, and avoiding interactions with complementary medications is essential for safe long-term management.