What effect does Class II antidysrhythmic medication have on the heart?

Class II antidysrhythmic medications primarily work by blocking beta-adrenergic receptors in the heart. The correct answer, which states that these medications decrease AV (atrioventricular) velocity, is accurate because beta-blockers reduce the conduction velocity through the AV node. This effect is beneficial in managing tachyarrhythmias by slowing down the electrical signals that can lead to rapid heart rates.

By decreasing AV nodal conduction, these medications help to restore a more regular rhythm and control the heart rate during episodes of atrial fibrillation or flutter, thus preventing the heart from beating too quickly and allowing for more effective filling of the heart chambers. Understanding this mechanism is crucial for applying pharmacological principles in clinical practice, especially in treating patients with dysrhythmias.