Which medical condition is defined as a sudden disruption of blood flow to the heart muscle?

The correct answer is myocardial infarction, which is characterized by a sudden interruption of blood flow to a section of the heart muscle. This interruption is typically caused by a blockage in one or more of the coronary arteries, often due to a buildup of plaque, which can rupture and form a clot. When blood flow is restricted, the affected area of the heart muscle begins to suffer from a lack of oxygen and nutrients, leading to tissue damage or death if blood flow is not restored quickly.

In contrast, heart failure refers to a chronic condition where the heart is unable to pump blood efficiently, rather than a sudden disruption of flow. Cardiac arrest is defined as the cessation of heart function, where the heart stops beating effectively, which can be a consequence of a myocardial infarction but is not a direct description of a disruption to blood flow. Atrial fibrillation is an irregular heartbeat that can lead to various complications, including an increased risk of stroke, but it does not directly define a sudden disruption of blood flow to the heart muscle. Thus, the most precise term for that acute situation is indeed myocardial infarction.