What causes angina
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Causes of Angina: An Overview
Coronary Artery Disease and Myocardial Ischemia
Coronary Artery Stenosis
The most common cause of angina is significant stenosis of one or more coronary arteries, typically when the stenosis is 70% or more of the artery's diameter. This condition restricts blood flow, leading to myocardial ischemia, especially during periods of increased oxygen demand such as physical exertion. Atherosclerosis, which involves the buildup of plaques in the coronary arteries, is responsible for about 90% of angina cases.
Nonocclusive Thrombus
In unstable angina, a nonocclusive thrombus on a preexisting atherosclerotic plaque can reduce myocardial perfusion. These thrombi are often found on complex, irregular lesions and can lead to continued thrombus formation, contributing to the angina. Inflammation within vulnerable plaques can also promote rupture and erosion, further exacerbating the condition.
Coronary Vasoconstriction and Spasm
Vasospastic Angina
Coronary vasoconstriction, particularly at the site of a preexisting stenosis, can contribute to myocardial ischemia and produce angina. This condition, known as vasospastic or Prinzmetal's angina, involves intense focal spasm of a segment of an epicardial coronary artery, which may or may not be involved by atherosclerosis . Vasospastic angina is characterized by ST-segment elevation and typically occurs at rest.
Microvascular Angina
Some patients experience angina despite having normal or non-obstructive coronary arteries. This condition, known as microvascular angina, is due to limited microvascular vasodilator capacity and heightened sensitivity to vasoconstrictor stimuli in the coronary microcirculation. Factors such as impaired endothelium-dependent and independent vasodilation and structural anomalies can also contribute to this type of angina.
Other Contributing Factors
Functional Causes
Functional causes of angina include conditions that affect the heart's ability to receive adequate oxygen. These include aortic valvular disease, thyroid disease, and pulmonary hypertension. Emotional or stressful events, extreme temperatures, and large meals can also trigger angina by increasing myocardial oxygen demand.
Inflammation and Infection
Inflammation and infection can play a role in the development of unstable angina. Activated leukocytes and other inflammatory markers are often found in patients with unstable angina, indicating a systemic inflammatory response that can exacerbate coronary artery disease .
Conclusion
Angina is primarily caused by myocardial ischemia due to significant coronary artery stenosis, nonocclusive thrombi, and coronary vasoconstriction. Other contributing factors include microvascular dysfunction, functional conditions affecting oxygen supply, and systemic inflammation. Understanding these causes is crucial for the effective diagnosis and management of angina.
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