Definition of Myocardial Infarction (Heart Attack)

1 million myocardial infarctions (MI or heart attacks) occur annually in the U.S., and are the most common cause of heart failure worldwide.

Helpful Highlights

  • Myocardial infarction (MI) or acute myocardial infarction (AMI) are the medical terms for a heart attack.

  • There are major and minor ("mini" or mild) heart attacks, and both are dangerous.

  • There are many risk factors for heart attacks that can be controlled.

  • Women and persons with diabetes are more likely to have atypical (unusual) symptoms of heart attack, and 20% of MI are silent (no symptoms).

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In medical terms, a heart attack is known as an acute myocardial infarction (AMI) or myocardial infarction (MI).

Myocardial infarction, also known as a heart attack, is a life-threatening condition that occurs when one or more areas of the heart muscle don't get enough oxygen.

The lack of oxygen occurs when blood flow to the heart muscle is blocked.

Lack of blood flow happens by several means, though is usually related to plaque build-up in one (or more) of the arteries that supply blood to the heart muscle (called coronary arteries).

Without blood flow, there is no oxygen, and without oxygen, the affected heart muscle will begin to die. If blood flow isn’t restored quickly, a heart attack can cause permanent heart damage and possibly death.

When a coronary artery is completely blocked, it is considered a "major" heart attack.

The coronary artery most susceptible and most commonly blocked is called the left main coronary artery (LMCA), which branches into the left anterior descending (LAD) and circumflex arteries that supply blood flow to the left chambers of the heart (atrium and ventricle).

The left ventricle is the large pump that sends blood to the rest of the body, and the left atrium fills the left ventricle. If either of these chambers fails, the heart cannot get blood to itself, the brain, or anywhere else in the body.

A blockage in the left coronary artery has long been referred to as, "the widow-maker" for good reason.

"Mini" (or mild) heart attack - Still dangerous

In a “mini” heart attack, blood flow to the heart is partially blocked. Symptoms are similar to those of a heart attack, including chest pain, though there is often less damage to the heart. That is, however, unless the attack is ignored and goes untreated, in which case "mini" can become "major."

Causes of a heart attack

Plaque is a hardened substance attached to artery walls that is made up of cholesterol, calcium deposits, and other cellular substances (like platelets and circulating fat). When plaque breaks (ruptures), a blood clot quickly forms, and the clot is the actual cause of the heart attack. The clot blocks the artery and prevents blood flow. When the blood and oxygen supply is cut off, muscle cells of the heart suffer damage and begin to die. Irreversible damage starts within about 30 minutes of blockage.

Plaque causes the clot and the clot causes the heart attack. What causes the plaque?

  • High blood pressure (chronic state: hypertension)

  • High cholesterol (LDL and triglycerides)

  • Diabetes

  • Smoking

  • Obesity

  • Stress and anxiety

  • Sedentary (inactive) lifestyle

  • Genetics (family history of heart disease - arteriosclerosis and atherosclerosis)

Controlling those things that can be controlled to reduce plaque build-up is essential to preventing a first heart attack, and make all the difference in whether there will be a second one after the first. And everything except genetics can be controlled.

Survival rates

Heart attack survival rates vary and depend on many factors - the type of heart attack, the person's general health, how quickly the person receives treatment, how quickly the arterial blockage is cleared, and how much of the heart muscle is permanently damaged.

Fatality rates were once as high as 50%, though today more than 90% of people hospitalized for heart attacks survive (rates are lower for those who don't receive rapid treatment and hospitalization).

Response time greatly affects survival rate. You may have heard the phrase, "Time is tissue." Quickly getting in an ambulance and to a hospital emergency room for treatment reduces the amount of damage to the heart muscle and increases the chance of survival.

Time is tissue

Some may think that if symptoms aren’t intense or severe it's not a heart attack. However, any and all symptoms associated with those of a heart attack should be evaluated immediately. Also, note that calling for an ambulance rather than driving to the emergency room can be life-saving. Paramedics can conduct an ECG (a.k.a. EKG) for transmission to an emergency physician to determine whether a heart attack is present, and if so, begin therapies right away.

Typical heart attack symptoms:

  • Chest pain (usually described as pressure or squeezing)

  • Shortness of breath, unable to catch a breath

  • Pain or tingling/numbness that extends up the left side of the neck to the jaw and/or down the left arm

  • Lightheadedness, nausea, and even vomiting

  • Clamminess or sweating

  • Change in skin color to pale, bluish, or grayish (can even be seen in dark skin tones)

Atypical (unusual) heart attack symptoms:

Women and people with diabetes are more likely to present with atypical symptoms, and 20% of heart attacks are silent (no symptoms).

  • Right-sided neck, jaw, and/or arm pain (vs left-sided)

  • Back pain

  • Stomach pain

  • Throat discomfort (feeling like something is lodged there or unable to swallow)

  • A sense of impending doom

  • No symptoms

If you notice the symptoms of a heart attack in yourself, your loved one, or anyone else, call 9-1-1 immediatelyDO NOT wait.

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