What effect do beta-blockers have on the heart?

Beta-blockers are primarily known for their role in managing cardiovascular conditions, particularly in reducing the workload on the heart. When beta-blockers are administered, they specifically bind to beta-adrenergic receptors, which are primarily found in the heart. The activation of these receptors normally increases heart rate and contractility; however, beta-blockers inhibit this process.

By blocking these receptors, beta-blockers lead to a decrease in both heart rate and the force of contraction (contractility) of the heart muscle. This results in a reduction of the heart's oxygen demand because the heart doesn’t have to pump as aggressively or as fast. Lowering the heart rate also allows more time for coronary blood flow to improve, thus supporting the overall efficiency of oxygen use by the heart.

The other options speak to functions that are contrary to the effects of beta-blockers—such as increasing oxygen demand or stimulating vessel constriction—which are not in line with the mechanism of action of these agents. Overall, the primary therapeutic effect of beta-blockers in the context of antianginal treatment is to decrease heart rate and contractility, helping to alleviate symptoms of angina by reducing myocardial oxygen consumption.