Complex sentence: Myocardial infarction (MI;) or acute myocardial infarction (AMI), commonly known as a heart attack, occurs when blood stops flowing properly to a part of the heart, and the heart muscle is injured because it is not receiving enough oxygen.
Split into simpler sentences: Myocardial infarction (MI;) or acute myocardial infarction (AMI) is the medical term for an event commonly known as a heart attack. An MI occurs when blood stops flowing properly to a part of the heart, and the heart muscle is injured because it is not receiving enough oxygen.