Atrial fibrillation: Propranolol

• Antiarrhythmic effects are due mainly to beta-adrenergic receptor blockade.

  • Normally, sympathetic drive results in increased in Ca²⁺ ,K⁺ ,and Cl^- currents.

• Increased sympathetic tone also increases phase 4 depolarization (heart rate goes up), and increases DAD (delayed afterdepolarizations) and EAD (early afterdepolarization) mediated arrhythmias.

  • These effects are blocked by beta-adrenergic receptor blockers.

• Beta-adrenergic receptor blockers increase AV conduction time (takes longer) and increase AV nodal refractoriness, thereby helping to terminate nodal reentrant arrhythmias.

• Beta-adrenergic receptor blockade can also help reduce ventricular following rates in atrial flutter and fibrillation, again by acting at the AV node.

• Adverse effects of beta blocker therapy can lead to fatigue, bronchospasm, depression, impotence, and attenuation of hypoglycemic symptoms in diabetic patients and worsening of congestive heart failure.

Category: Pharmacology Notes