Angina pectoris pathophysiology
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Myocardial Ischemia and Oxygen Imbalance in Angina Pectoris Pathophysiology
Angina pectoris is primarily caused by an imbalance between the heart muscle’s oxygen supply and its oxygen demand. This mismatch leads to myocardial ischemia, which is the underlying mechanism for the chest pain experienced during angina episodes Costa1997Zahr2013Kaski2016+3 MORE. The main factors that increase myocardial oxygen demand include higher heart rate, increased contractility, elevated preload and afterload, and increased blood pressure Zahr2013Kaski2016Julius1997. When the coronary arteries cannot deliver enough oxygen-rich blood to meet these demands, ischemia and angina occur Costa1997Zahr2013Kaski2016+3 MORE.
Coronary Artery Disease and Atherosclerosis: Key Contributors
The most common cause of angina pectoris is coronary artery disease, where atherosclerotic plaques build up in the coronary arteries, narrowing the vessel lumen and restricting blood flow Costa1997Zahr2013Kaski2016+3 MORE. This narrowing becomes especially problematic during times of increased oxygen demand, such as physical exertion or emotional stress, leading to the classic symptoms of stable angina Quyyumi1990Gobel1982. In stable angina, the plaques are typically uncomplicated, while in unstable angina, plaque rupture, fissures, or thrombus formation can further reduce blood flow and increase the risk of heart attack .
Endothelial Dysfunction and Microvascular Angina
Endothelial dysfunction is now recognized as an important early event in the development of atherosclerosis and angina. Even in the absence of significant blockages in the large coronary arteries, dysfunction in the smaller vessels (microvascular dysfunction) can lead to angina symptoms . This is sometimes referred to as microvascular angina and is more common in patients who have chest pain but normal coronary angiograms .
Other Causes: Aortic Stenosis and Hypertrophic Cardiomyopathy
While atherosclerosis is the most common cause, angina pectoris can also result from other heart conditions. Severe aortic stenosis, hypertrophic obstructive cardiomyopathy, and hypertensive heart disease can all cause angina by increasing the workload of the heart or by reducing coronary blood flow, even when the coronary arteries themselves are not blocked Quyyumi1990Cohn1972. In aortic stenosis, for example, increased wall stress and reduced coronary flow reserve can lead to myocardial ischemia and angina, even in the absence of coronary artery disease .
Dynamic and Functional Mechanisms
In addition to fixed blockages, dynamic changes such as coronary artery spasm or changes in vasomotor tone can also reduce blood flow and trigger angina Zahr2013Quyyumi1990Julius1997. These functional mechanisms can play a role in both stable and unstable angina, and may explain symptoms in patients without significant atherosclerotic disease Zahr2013Quyyumi1990Julius1997.
Conclusion
The pathophysiology of angina pectoris centers on an imbalance between myocardial oxygen supply and demand, most often due to atherosclerotic narrowing of the coronary arteries. However, other factors such as endothelial dysfunction, microvascular disease, dynamic changes in vessel tone, and non-atherosclerotic heart conditions can also contribute. Understanding these mechanisms is crucial for effective diagnosis and management of angina pectoris Costa1997Zahr2013Kaski2016+5 MORE.
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Stable Angina Pectoris: Definition, Clinical Presentation and Pathophysiologic Mechanisms
Angina pectoris is a clinical presentation of myocardial ischaemia caused by obstructive coronary atherosclerosis, with various pathophysiological mechanisms and potential exacerbating factors.
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