What Is a Heart Attack?A heart attack, also called a myocardial infarction (MI), is the most severe form of acute coronary syndrome (ACS). MIs, like all forms of ACS, are usually triggered by the rupture of a plaque within a coronary artery. This plaque rupture causes a blood clot to form, leading to blockage of the artery. The portion of the heart muscle being supplied by the blocked artery then begins to die. It's the death of heart muscle that defines an MI.
What Are the Consequences of a Heart Attack?To a large degree, the outcome of an MI depends on how much of your heart muscle dies, which, in turn, is related to which of your coronary artery is blocked, and where in the artery the blockage occurs. (A blockage near the origin of an artery will affect more heart muscle than a blockage farther down the artery.)
If the heart muscle damage is severe, it is possible to develop acute heart failure during the MI itself, which is a very dangerous condition. If the amount of heart muscle damage is less severe but still significant, you can develop heart failure later on. So, taking steps to prevent heart failure after an MI, or aggressively treating heart failure should it develop, is an extremely important aspect to treating an MI.
An MI can also produce dangerous heart arrhythmias. During the acute MI itself, electrical instability occurs that may cause ventricular tachycardia (VT) and ventricular fibrillation (VF). Later, the scar tissue that results from the healing process can cause a permanent electrical instability. So, unfortunately, cardiac arrest and sudden death are risks both during an acute MI and after full recovery from an MI.
Why Are the First Few Hours of a Heart Attack Critical?For anyone having an MI, getting rapid medical attention is absolutely critical for two reasons:
- Most of the cardiac arrests seen with acute MIs occur within the first few hours. If the cardiac arrest happens after you have come under medical care, there is an excellent chance it can be successfully treated; otherwise the odds of surviving a cardiac arrest are very low.
- Both the short-term and the long-term consequences of an MI are largely determined by how much of your heart muscle dies. With rapid and aggressive medical treatment, the blocked artery can usually be opened quickly, thus preserving most of the heart muscle that is at risk of dying. If treatment is given within three or four hours, much of the permanent muscle damage can be avoided. But if treatment is delayed beyond five or six hours, the amount of heart muscle that can be saved drops off significantly. After about 12 hours, the damage is usually irreversible.