Which of the following statements regarding beta-blockers is true?

Beta-blockers are a class of medications that primarily work by blocking the effects of adrenaline on the beta-adrenergic receptors in the heart. This leads to several cardiovascular effects, one of which is the reduction of the heart's workload. By decreasing heart rate and the force of contraction, beta-blockers lower myocardial oxygen demand, making them particularly useful in conditions like hypertension, heart failure, and angina.

The ability of beta-blockers to decrease the workload of the heart helps in preventing complications related to excessive cardiac stress. This is vital in managing various cardiovascular conditions, as it allows the heart to function more efficiently without straining. Reducing the workload also assists in lowering blood pressure and improving overall cardiac function.

Other choices do not align with the primary effects of beta-blockers. They are not aimed at increasing blood pressure, contractility, or cardiac output; rather, they work to stabilize these parameters to prevent adverse cardiovascular events. Thus, the truthful statement regarding beta-blockers pertains to their ability to decrease the workload of the heart.