Final answer:
β-blockers are a type of sympatholytic drug used to treat cardiovascular diseases such as heart failure and irregular heartbeats.
Step-by-step explanation:
Based on the information provided, the drug being referred to is a sympatholytic drug, specifically a β-blocker. These drugs are commonly used to treat cardiovascular diseases like heart failure and irregular heartbeats. By blocking the β-receptors associated with vasoconstriction and cardioacceleration, they can improve cardiac function by dilating blood vessels and preventing an increase in heart rate.