Hypertension
Beta blockers are used to treat and manage hypertension to lower high blood pressure. Blood pressure is the force needed to pump blood around the body. Blood pressure measurements are divided into systolic pressure, which is when the heart contracts forcing blood out into the arteries, and diastolic when the heart rests and fills with blood. Hypertension is high blood pressure at rest and causes reduced blood flow, increases the force needed to pump blood around the body, increases workload on the heart and increases oxygen demand. This can cause damage to blood vessels as well as end organ tissue damage to the kidneys, eyes and nerves. Hypertension also increases risk of cardiovascular disease, including stroke and heart attack.
Heart conditions
Beta blockers are used to treat and manage several cardiovascular conditions, including:
- Angina, which is caused by narrowing of the arteries that supply the heart (coronary arteries) reducing blood flow to the heart and causing symptoms like discomfort or pain in the chest and breathlessness on exertion.
- Heart failure, which is inefficient pumping of the heart so that it cannot maintain an adequate circulation of blood and is due to weakened heart muscle caused by a previous heart attack, high blood pressure or an enlarged heart (cardiomyopathy). Symptoms include oedema (fluid in the tissues) and breathlessness.
- Irregular heart beat also known as dysrhythmia or arrhythmia, which is due to abnormal electrical activity to the heart resulting in a heart beat that is too fast or slow or irregular. It has several known causes, including high blood pressure or heart disease, with symptoms including heart palpitations and shortness of breath.
- Heart attack (myocardial infarction), which is when blood flow to the heart is blocked and the heart muscle does not get enough oxygen so that cells begin to die. Beta blockers can help prevent serious damage to the heart during early stages of acute myocardial infarction and can help with prevention of further heart attacks.
How do beta blockers work?
Beta blockers work by binding to beta adrenergic receptors in the heart blocking the action of chemicals like adrenaline that are released by the adrenal glands in response to nerve stimulation during physical and mental stress. Adrenaline stimulates increased heart rate and constriction (narrowing) of blood vessels and beta blockers reverse this action to slow heart rate, dilate (widen) blood vessels, lower blood pressure, and increase blood flow and oxygen to the heart. Several beta blockers are available, including the cardioselective beta 1 receptor blockers atenolol, metoprolol, carvedilol; also nadolol, which is non-selective and also binds to beta 2 receptors in the bronchial smooth muscle in the lungs and vascular smooth muscle.