ACE (angiotensin converting enzyme) inhibitors are a type of medicine used to treat heart attacks, high blood pressure, and heart failure. It is also frequently prescribed for a condition called "left ventricular systolic dysfunction," which is a decreased function of the left part of your heart. ACE inhibitors can help reduce the risk of death from a heart attack if taken within 24 hours of the first symptoms of a heart attack. Continued use may help prevent heart failure. ACE inhibitors work by stopping the production of a hormone that can narrow your blood vessels. This helps reduce the pressure in your heart, lowering your blood pressure.