What effect does a beta blocker have on the heart?

Beta blockers are a class of medications that primarily work by blocking the effects of the hormone epinephrine, also known as adrenaline. This action results in a decrease in heart rate and a reduction in the force of contraction of the heart muscle, which collectively lead to lower blood pressure. By inhibiting the heart rate, beta blockers help to reduce the overall workload on the heart, making them particularly beneficial in conditions like hypertension, heart failure, and certain arrhythmias.

This property is critical in managing cardiovascular diseases as it helps prevent complications related to high blood pressure and reduces cardiac oxygen demand. By lessening the heart's workload, beta blockers can improve exercise tolerance and potentially decrease the risk of further heart issues.

The other options do not accurately represent the primary actions of beta blockers. For instance, while beta blockers can have some impact on blood vessels indirectly, their main function is not to cause dilation but rather to slow down the heart and reduce blood pressure. Additionally, they do not increase heart contractility; in fact, they typically decrease it, which helps in managing heart-related conditions. Furthermore, beta blockers do not cause angina; they are often used to manage symptoms of angina pectoris by reducing heart workload and oxygen demand.