ACS is a bit of a catch all term for sudden reduced blood flow (ischemia) to the heart .
I only know of the of the CDC acknowledging increased myocarditis in young men after recieving the Moderna vaccine. But, there are journal articles from other countries documenting myocarditis in both mRNA vaccines. Also, the FDA is seeking to restrict access to the mRNA trial data (from FOIA requests) for 55 years for some reason.
I am really only familiar with ASC thru the surgical risk calculator that assesses your risk of cardiac ischemia during or after surgery (where high blood pressure, high cholesterol and smoking are contributing risks). The two mosts serious conditions related to ACS are a Myocardial Infarction (Heart Attack) resulting in cell death that damages or destroys the heart. And, Infarction with ischemia and no cell death. Leaving your function permanently altered and at much higher risk of severe heart attacks leading to death.