How do beta-blockers like metoprolol help in angina and post-MI management, and what key adverse effect must nurses monitor?

• A. They increase heart rate to improve perfusion.
• B. They dilate arteries to lower afterload.
• C. They block beta-adrenergic receptors reducing heart rate and contractility, lowering myocardial oxygen demand.
• D. They inhibit the renin-angiotensin-aldosterone system.

Answer: (C)

Beta-blockers work by blocking beta-1 receptors in the heart, which lowers both heart rate and the force of contraction. That reduction cuts the heart’s oxygen demand, so during chest pain (angina) there’s less mismatch between oxygen supply and demand, easing symptoms. After a myocardial infarction, the same effects help by decreasing myocardial workload, which can lessen further injury and reduce the risk of dangerous arrhythmias and death. The most important adverse effect to monitor is bradycardia from the slower heart rate; hypotension can also occur. Nurses should routinely check the pulse and blood pressure and be alert for dizziness, fatigue, or signs of poor perfusion, adjusting treatment if the heart rate becomes too slow.