What is angina pectoris?
Angina pectoris (Latin for chest pain) is pain that is caused by injury to the heart muscle (myocardium) during times of increased cardiac activity as a result of impaired blood flow and reduced oxygen supply. Angina pain is often described as a dull, constricting or crushing pain that is felt behind the sternum (retrosternal).It may also be described as a squeezing, burning or heaviness.
What does angina pectoris mean?
Angina pectoris is NOT a heart attack. As discussed below, angina pectoris is a sign of myocardial ischemia (injury to the heart muscle) and not a myocardial infarction (heart attack ~ death of heart muscle). This means you heart muscle is getting too little oxygen for its needs. However, angina pectoris often precedes a heart attack and can exist for months or years before a heart attack occurs. It should therefore be seen as a warning sign of an impending heart attack.
Angina pectoris is most commonly due to progressive narrowing of the coronary artery so if left untreated the attacks will get worse and more frequent until a person has a heart attack. Since the arm, neck and heart develop from the same embryonic tissue, angina typically causes pain to radiate to the arm, particularly left arm, and the neck. It tends to last for a few minutes and subside with rest or the use of nitrates.
Why does angina occur?
The myocardium of the heart is constantly working and pumps blood throughout the body by contracting and relaxing. Being such an active part of the body, it needs a constant supply of oxygen and nutrients, which means a good blood supply. As the activity increases, the heart has to work harder and faster. A slight restriction of the blood supply may not cause any symptoms or damage when at rest or with moderate activity.
However, if there is increased activity like during exercise, then the heart needs an intact blood supply with sufficient oxygen availability. If this is not available then the heart muscle tissue undergoes damage known as ischemia. The muscle does not die but is injured. If this injury is severe or persistent, it may lead to death to a portion of the heart muscle which is known as an infarct (myocardial infarction or heart attack).
Pathophysiology of Angina Pectoris
The coronary arteries of the heart supply oxygen-rich blood primarily to the heart muscle. These arteries have numerous branches to ensure that there is adequate coverage to the heart muscle. This is explained further under blood supply to the heart.
Clogged coronary arteries most often arises as a result of atherosclerosis. Here fatty plaques develop under the inner lining of the artery and is associated with high blood cholesterol, high blood pressure and cigarette smoking among other risk factors. The build up of these plaques gradually narrows the lumen of the artery over months or even years. It is usually asymptomatic meaning that a person does not know that is occurring because there are no symptoms.
Once the occlusion reaches a point where the blood supply to the heart muscle is severely impaired, it can cause pain during physical activity – this pain (angina pectoris) is a result of damage to the heart muscle. In severe cases, the blockage may be so severe and further compounded by the sudden lodging of a clot, that the heart muscle will die (heart attack or myocardial infarction).
Different Types of Angina
There are three types of angina :
- Stable angina or typical angina pectoris
- Prinzmetal variant angina
- Unstable angina or crescendo angina
Stable angina or typical angina pectoris is the most common form of angina. It occurs as a result of increased cardiac workload associated with physical activity or emotional stress. The narrowed coronary artery cannot deliver enough blood that is necessary for the heart’s needs and this causes injury as described above. The pain is relieved by rest or the use of nitrates. The process related to this form of angina is well understood.
Prinzmetal Variant Angina
This is an uncommon form of angina that occurs in episodes without any clearly defined trigger factors. It is not related to physical activity or emotional stress but is a consequence of a spasm in the coronary artery which worsens the narrowing already caused by moderate atherosclerosis. It also responds well to nitrates. This form of angina is less well understood when compared to stable angina.
Unstable angina, also known as crescendo angina, is a progressing form of angina that occurs with physical exertion and eventually even at rest. The frequency of pain increases, lasts longer with successive attacks and with time the person’s ability to undertake activity reduces significantly. It is believed to be a consequence of more than one factor – atherosclerosis, coronary artery spasm and possibly even a blood clot (thrombus or embolus) all at the same time. It tends to occur prior to a heart attack and is considered as a warning signal of an impending heart attack (myocardial infarction). Therefore it is also known as preinfarction angina.