Doctors use β-blocker drugs to treat many conditions, including high blood pressure, chest pain (angina), heart attacks, and migraine headaches. There are several types of β-blockers. Cardioselective β-blockers (β-1–blockers) act mainly on the heart. They slow heart rate, decrease blood pressure, and reduce the heart's workload. Other β-blockers act on the heart but also may narrow blood vessels throughout the body and the airways to the lungs (bronchi).