Isoproterenol is a non-selective activator or agonist of beta-1 and beta-2 receptors. It is very rarely used in the clinical context for treatment of heart block.

Key Points

  • Isoproterenol
    • Mechanism
      • Beta-1 Receptor Agonist
        • Acts on heart to increase cardiac output by increasing heart rate and contractility
      • Beta-2 Receptor Agonist
        • Acts on blood vessels to cause vasodilation, decreasing systemic vascular resistance and blood pressure
    • Indications
      • Heart Block and Bradycardia
        • Increases dromotropy (AV nodal conduction) and heart rate
      • Electrophysiologic evaluation of tachyarrhythmias
        • May provoke tachyarrhythmias in patients
      • May worsen ischemia
        • Increased cardiac output by beta-1 stimulation increases myocardial oxygen demand, which can induce ischemia
    • Adverse Effects
      • Reflex Tachycardia
        • Beta-2 stimulated vasodilation reduces vascular resistance and blood pressure, which causes a compensatory increase in heart rate