Final answer:
A heart attack is a more serious and immediately life-threatening condition than heart failure. It occurs when there is a blockage in a coronary artery, leading to the death of cardiac muscle cells.
Step-by-step explanation:
A heart attack is generally a more serious and immediately life-threatening condition compared to heart failure. A heart attack, also known as a myocardial infarction (MI), occurs when there is a blockage in a coronary artery, preventing blood and oxygen from reaching a region of the heart, causing death of the cardiac muscle cells. On the other hand, heart failure refers to the heart's inability to pump blood effectively, which can be a chronic condition.