A patient who has had an MI is taking a beta-blocker. What is the main benefit of beta-blocker therapy for this patient?

Choice A rationale Beta-blockers do not cause vasodilation of the coronary arteries. In some cases, non-selective beta-blockers may even cause unopposed alpha-1 receptor stimulation, leading to vasoconstriction. Their primary benefit post-MI is not related to vasodilation but to their effects on cardiac work. Choice B rationale Beta-blockers decrease the force of cardiac contraction (negative inotropic effect) rather than increasing it. This reduction in contractility, along with a decreased heart rate, reduces the heart's workload and oxygen demand, which is beneficial after a myocardial infarction. Choice C rationale Beta-blockers slow the heart rate (negative chronotropic effect) by blocking beta-1 receptors in the sinoatrial (SA) node. This action reduces myocardial oxygen demand, decreases the workload on the heart, and prolongs diastole, allowing for improved coronary artery filling. This is the main benefit for a post-MI patient. Choice D rationale While beta-blockers are used to treat hypertension and can help maintain blood pressure, the primary benefit for a post-MI patient is the reduction of myocardial oxygen demand by slowing the heart rate and decreasing contractility. This action helps to prevent further damage to the heart muscle.