What is a beta-blocker used for?

A beta-blocker is a medication primarily used to reduce the workload on the heart. It achieves this by blocking the effects of adrenaline, which in turn slows down the heart rate and decreases the force of heart contractions. This reduction in heart rate and contractility allows the heart to pump more efficiently and decreases the overall oxygen demand of the heart muscle, making beta-blockers particularly useful in treating conditions such as hypertension, heart failure, and certain types of arrhythmias.

The other options involve different mechanisms or treatments. For instance, increasing heart rate would be counterproductive in the context of what beta-blockers are designed to do. Dissolving blood clots is the role of anticoagulants or fibrinolytics, but this is not related to the action of beta-blockers. Finally, enhancing oxygen delivery in the body is not the direct function of beta-blockers, as their primary role is to modulate heart activity rather than directly improving oxygen transport.