The primary cause of acute coronary syndrome in patients with heart disease is typically:

The primary cause of acute coronary syndrome (ACS) in patients with heart disease is atherosclerosis. Atherosclerosis is a progressive condition characterized by the buildup of fatty deposits, cholesterol, and other substances within the arterial walls, leading to the narrowing of the arteries over time. This narrowing restricts blood flow to the heart muscle, especially during increased physical activity or stress when the heart requires more oxygen.

When the atherosclerotic plaques become unstable, they can rupture, leading to the formation of a thrombus (blood clot). This thrombus can further obstruct blood flow, resulting in conditions that fall under the umbrella of acute coronary syndrome, including unstable angina and myocardial infarction (heart attack). The association between atherosclerosis and ACS is well-documented and is a key focus in the management and prevention of heart disease, as addressing the underlying atherosclerotic changes can significantly reduce the risk of ACS events.

Other causes listed, such as atrial damage, coronary artery spasm, and coronary artery rupture, may contribute to cardiac issues but are not the primary drivers of ACS in patients with established heart disease. The complexity and multifactorial nature of heart disease makes atherosclerosis the most significant and prevalent cause of acute coronary syndrome.