Pathophysiology
Clinical meaning
Chronic sympathetic nervous system activation in heart failure increases heart rate, myocardial oxygen demand, and direct catecholamine toxicity to cardiomyocytes (beta-1 receptor downregulation, calcium overload, apoptosis, fibrosis). Beta-blockers counteract this maladaptive neurohormonal activation, reducing mortality by 30-35% in HFrEF. Only THREE beta-blockers have mortality benefit in HFrEF: carvedilol, metoprolol succinate (extended-release), and bisoprolol. These are NOT interchangeable โ other beta-blockers (atenolol, propranolol, metoprolol tartrate) lack HF mortality data. Carvedilol is a non-selective beta-blocker (beta-1 and beta-2) with additional alpha-1 blocking activity (vasodilation) and antioxidant properties. It causes more blood pressure lowering than beta-1 selective agents and is preferred in patients with concomitant hypertension. Metoprolol succinate (Toprol-XL) is beta-1 selective, causing less bronchospasm than carvedilol, making it preferred in patients with reactive airway disease. Bisoprolol is the most beta-1 selective and has the longest half-life, enabling once-daily dosing. The critical principle is 'start low, go slow': beta-blockers must be initiated at the lowest dose during clinical stability (not during acute decompensation) and titrated every 2 weeks to maximum tolerated dose. During initiation, patients may experience transient worsening of HF symptoms from...