Pathophysiology of angina
Angina is caused by an imbalance between myocardial oxygen supply and demand that results in myocardial ischaemia. Myocardial ischaemia occurs where the coronary arteries deliver insufficient oxygenated blood to the heart muscles resulting in hypoxia. Myocardial ischaemia associated with angina does not result in cell death or tissue necrosis.3
The supply of oxygen to the myocardium is determined by the coronary blood flow and the level of oxygen within the blood. Coronary blood flow can be significantly reduced by the presence of atherosclerotic plaques in the coronary arteries. As these plaques increase in size they occlude the coronary arteries, reducing the arterial lumen and impairing coronary blood flow.
Factors that can increase the myocardial oxygen demand include:
- Emotional stress such as fright, anger or stress
- Increased physical activity such as exercise or sex
- Additional features including cold weather, fever or overeating