What is the leading cause of ACS?

In the realm of healthcare and particularly cardiovascular medicine, we often encounter various acronyms that represent significant conditions. One such acronym stands for "Acute Coronary Syndrome" or ACS, a potentially life-threatening medical emergency. So, I must inquire, what is the leading cause of ACS? Is it the buildup of plaque within the coronary arteries, leading to a blockage of blood flow? Or perhaps it's a spasm of the coronary artery, causing a temporary reduction in blood supply? Understanding the root cause of ACS is crucial in devising effective treatment strategies and preventing future occurrences.