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Myocardial Infarction (MI) or Heart Attack

Definition and Overview

Myocardial infarction, more commonly known as a heart attack, prevents vessels from supplying blood to the heart and is considered a medical emergency. Heart attacks lead to 12.6% of deaths worldwide. Recent advancements in technology have made it possible for more people to survive and resume fairly normal lives. 

Causes and Symptoms

Blocking the arteries (usually by a blood clot) that supply the heart with blood usually causes a myocardial infarction. The arteries become hardened and build up plaque over many years. This change can be caused by cholesterol that accumulates and damages the arteries. There is a resulting lack of oxygen in the heart tissue that normally receives blood from the blocked artery, and when this occurs the heart muscle is damaged and begins to die. If tissue death is extensive enough the heart will stop beating and cause death. The lack of blood to parts of the heart can also cause the heart to beat irregularly, which can on its own be deadly. 

Different people will often experience very different symptoms during a heart attack. In women, symptoms can often be overlooked or mistaken for other things as they tend to be less pronounced or not seen at all. Signs of an attack include pressure, fullness, or squeezing in the center of the chest and a pain that radiates away from the chest to the shoulder, arm or jaw. Signs also include shortness of breath, sweating, prolonged abdominal pain, nausea, vomiting, lightheadedness, and fainting. Heart attacks can occur very suddenly, but many people can recognize the symptoms before the attack occurs.

Some risk factors include smoking, obesity, high cholesterol and blood pressure, Type II diabetes, stress, alcohol, and family history of heart problems.

Diagnosis A myocardial infarction can be diagnosed by a physician after looking at blood tests, as well as by using an electrocardiogram to examine the electrical activity of the heart. The doctor can also do other tests to examine the extent of the damage such as an angiogram, an echocardiogram, or a chest X-ray. 

Treatment and Prognosis

When having a heart attack it is important to immediately call for emergency medical help, and to take prescribed nitroglycerine or other medication. If someone is found unconscious from a heart attack it is important to call for emergency help and to then perform CPR, especially performing the chest compressions to keep blood flowing throughout the body. When emergency help arrives a defibrillator is usually necessary to restart the heart beating properly.

Once in the hospital there are a number of medications that can be given to try to prevent more clots in the heart and to try to break up the clot in the vessel that caused the ischemia in the first place. In addition to the medication it may be necessary to perform surgery on the heart to remove the clot and to repair the damaged vessel and heart tissue. After this it is important to let the patient recover and the heart to try to regain function. It is also important to discuss lifestyle changes to try to prevent an event such as this from recurring.

Approximately 1/3 of people will die of their heart attack; if the patient survives the first two hours of the attack then they are likely to recover sometimes even fully. The patient is still at risk of suffering a subsequent heart attack, especially if risk factors are not modified.