Both beta-blocking agents and calcium channel blockers are commonly used to treat AFF in the ED. Metoprolol is the most commonly used beta-blocker; and diltiazem is the most frequently used calcium channel antagonist.[8] Diltiazem was released by the FDA for treatment of AFF in 1992. Shreck et al. were the first to demonstrate both the efficacy of diltiazem in the ED management of AFF with rapid rate and its clear superiority over the previously most commonly used pharmacologic agent, digoxin.