Angina, also known as angina pectoris, is chest pain or pressure, usually caused by insufficient blood flow to the heart muscle (myocardium). It is most commonly a symptom of coronary artery disease.
Angina is typically the result of partial obstruction or spasm of the arteries that supply blood to the heart muscle. The main mechanism of coronary artery obstruction is atherosclerosis as part of coronary artery disease. Other causes of angina include abnormal heart rhythms, heart failure and, less commonly, anemia. The term derives from the Latin angere ("to strangle") and pectus ("chest"), and can therefore be translated as "a strangling feeling in the chest".
There is a weak relationship between severity of angina and degree of oxygen deprivation in the heart muscle, however, the severity of angina does not always match the degree of oxygen deprivation to the heart or the risk of a myocardial infarction (heart attack). Some people may experience severe pain even though there is little risk of a heart attack. Others may have a heart attack and experience little or no pain. In some cases, angina can be quite severe. Worsening angina attacks, sudden-onset angina at rest, and angina lasting more than 15 minutes are symptoms of unstable angina (usually grouped with similar conditions as the acute coronary syndrome). As these may precede a heart attack, they require urgent medical attention and are, in general, treated similarly to myocardial infarction.
In the early 20th century, severe angina was seen as a sign of impending death. However, modern medical therapies have improved the outlook substantially. Middle-age patients who experience moderate to severe angina (grading by classes II, III, and IV) have a five-year survival rate of approximately 92%.
Classification
Stable angina
Also known as 'effort angina', this refers to the classic type of angina related to myocardial ischemia. A typical presentation of stable angina is that of chest discomfort and associated symptoms precipitated by some activity (running, walking, etc.) with minimal or non-existent symptoms at rest or after administration of sublingual nitroglycerin. Symptoms typically abate several minutes after activity and recur when activity resumes. In this way, stable angina may be thought of as being similar to intermittent claudication symptoms. Other recognized precipitants of stable angina include cold weather, heavy meals, and emotional stress.
Unstable angina
Unstable angina (UA) (also "crescendo angina"; this is a form of acute coronary syndrome) is defined as angina pectoris that changes or worsens.
It has at least one of these three features: it occurs at rest (or with minimal exertion), usually lasting more than 10 minutes it is severe and of new-onset (i.e., within the prior 4–6 weeks) it occurs with a crescendo pattern (i.e., distinctly more severe, prolonged, or frequent than before).
UA may occur often occur unpredictably and even at rest, which may be a serious indicator of an impending heart attack. The primary factor differentiating unstable angina from stable angina (other than symptoms) is the underlying pathophysiology of the atherosclerosis. The pathophysiology of unstable angina is the reduction of coronary blood flow due to transient platelet aggregation on apparently normal endothelium, coronary artery spasms, or coronary thrombosis.
The process starts with atherosclerosis, progresses through inflammation to yield an active unstable plaque, which undergoes thrombosis and results in acute myocardial ischemia, which, if not reversed, results in cell necrosis (infarction). Studies show that 64% of all unstable anginas occur between 22:00 and 08:00 when patients are at rest.
In stable angina, the developing atheroma (a fatty plaque) is protected with a fibrous cap. This cap may rupture in unstable angina, allowing blood clots to precipitate and further decrease the area of the coronary vessel's lumen or the interior open space within an artery. This explains why, in many cases, unstable angina develops independently of activity.