What effect do beta blockers have when used to treat angina?

Beta blockers are primarily used in the management of angina due to their ability to decrease heart rate and reduce myocardial oxygen demand. By decreasing heart contractility, beta blockers help to relieve the strain on the heart during episodes of angina. This results in more efficient functioning of the heart and reduced symptoms associated with angina attacks.

When beta blockers lower the contractility of the heart, they ultimately reduce the workload of the heart muscle. This is crucial because angina typically occurs when the demand for oxygen by the heart exceeds the supply available, often due to coronary artery disease. By decreasing the force of contraction, beta blockers help to ensure that the heart does not require as much oxygen, thereby alleviating the symptoms of angina.

In contrast, the other options would not achieve the desired outcome in treating angina. For example, increasing heart rate or oxygen demand would exacerbate angina symptoms rather than alleviate them. Decreasing afterload may also not directly address the underlying problem of oxygen supply versus demand. Thus, the choice of decreased heart contractility aligns perfectly with the goal of managing angina effectively.