Angina in coronary artery disease
Acidic substances, such as lactic acid or other analgesic products, such as histamine, kinins, or cellular proteolytic enzymes, are not eliminated rapidly enough by the slow-moving coronary blood flow. .
Normally, a person cannot “feel” his or her heart, but ischemic heart muscle often causes pain that is sometimes intense. It is not clear exactly what causes this pain, but it is believed that ischemia causes the muscle to secrete acidic substances, such as lactic acid, or other pain-relieving products, such as histamine, kinins, or cellular proteolytic enzymes, are not eliminated rapidly enough by the slow-moving coronary blood flow.
High concentrations of these abnormal products then stimulate pain nerve endings in the myocardium, sending pain impulses through sensory nerve fibres into the central nervous system.
In most people who maintain constant constriction of the coronary arteries, a heart attack, known as angina, begins whenever the cardiac load becomes too great in relation to blood flow. coronary arteries are available. This pain is usually felt below the sternum, and in addition, it is often referred to as the distal surface areas of the body, most commonly in the left arm and left shoulder but also frequently to the neck and even the neck. on the side of the face. The reason for this pain distribution is that during infancy, the heart originates in the neck, as well as the arm. Thus, both the heart and these surface areas of the body receive pain-relieving nerve fibres from the same segments of the spinal cord.
Most people with chronic angina experience pain during exercise or when experiencing emotions that increase cardiac metabolism or temporarily constrict the coronary arteries due to sympathetic nerve signals. Angina is also aggravated by cold temperatures or by eating well, both of which increase the heart's workload. The pain usually lasts only a few minutes. However, some patients have such severe and persistent ischemia that the pain is present all the time. The pain is often described as hot, squeezing, and constricting and of such a quality that it often causes the patient to stop all bodily activities.
Certain vasodilators, when used during an acute attack of angina, can often provide immediate relief. The commonly used short-acting vasodilators are nitro-glycerine and other nitrate drugs. Other vasodilators, such as angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, calcium channel blockers, and ranolazine, may be beneficial in the treatment of chronic stable angina.
Another class of drugs used to treat persistent angina are beta-blockers, such as propranolol. These drugs block sympathetic beta-adrenergic receptors, preventing sympathetic enhancement of heart rate and heart metabolism during exercise or emotional episodes. Thus, treatment with beta-blockers reduces the heart's need for additional metabolic oxygen during stress. For obvious reasons, this therapy can also reduce the number of angina attacks, as well as their severity.