What Causes a Heart Attack?

A heart attack, also called myocardial infarction (MI), occurs when blood flow to the heart is suddenly interrupted. This can lead to damage to the heart muscle. Treatment is the only way to avoid irreversible damage from a heart attack.

This article covers heart attack causes, triggers, warning signs, and prevention.

Main Cause: Coronary Heart Disease

Most heart attacks are caused by coronary heart disease, also called coronary artery disease.

Atherosclerosis leads to coronary heart disease. In atherosclerosis, plaque accumulates inside the arteries. Cholesterol, fat, calcium, and inflammatory blood cells form the plaque. As it builds up, the arteries narrow, and there's a reduced supply of blood going to the heart and other organs. This buildup can start as early as childhood.

Plaques can rupture, leading to the formation of blood clots. If the blood clot is big enough, it can partially or completely block blood flow to the heart, causing a heart attack.

Nearly 50% of Americans ages 45 to 84 have atherosclerosis. Yet they may not know it. In its early stages, atherosclerosis may not have any warning signs. Sometimes, nearby blood vessels will compensate to make up for reduced blood flow to the heart from the affected arteries.

Many things can increase the risk of developing coronary heart disease, including:

• Getting older, specifically starting around age 45 for men and age 55 for women
  
• Having a family history of coronary heart disease
• Having high blood pressure
• Having high cholesterol
• Not getting enough physical activity
• Not getting enough sleep
• Environmental factors like air pollution

More risk factors are discussed in the following "What Raises the Risk of a Heart Attack?" section. These are the same risk factors associated with coronary heart disease.

Other Heart Attack Causes

In addition to coronary heart disease, a condition called MINOCA, short for myocardial infarction with non-obstructive coronary arteries, can also cause a heart attack. This is more common in younger people in general and specifically younger women of color.

With MINOCA, if healthcare providers do a heart imaging test called an angiogram, they would not see any signs of heart disease. However, there is poor blood flow to the heart, which leads to a heart attack.

MINOCA can have several causes:

• Plaque buildup that causes erosion rather than a disruption in an artery. Again, this type of buildup can't be seen on imaging.
• Coronary artery spasms, or quick, sudden narrowing of arteries that take blood to the heart
• A coronary artery embolism is when a blood clot goes through the bloodstream and gets stuck in a coronary artery, blocking blood flow. This is more common in pregnant people and those with atrial fibrillation (an abnormal heart rhythm) or thrombocytopenia (low numbers of platelets, which are blood cells involved in clotting).
• Spontaneous coronary artery dissection, or SCAD, which occurs when a blood vessel tears. Although not common, SCAD is the most common cause of heart attacks in pregnant and post-partum people.
  

Like with coronary heart disease, high blood pressure, high cholesterol, and smoking can raise the risk for MINOCA. However, these health issues are less common in those having heart attacks from MINOCA compared with those having heart attacks from coronary heart disease.

Less Common Causes of Heart Attack

Here is more information on the less common causes of a heart attack, including drug misuse and lack of oxygen.

Misuse of Drugs

Certain recreational drugs can raise the risk of a heart attack, including:

• Cocaine
• Ecstasy
• Heroin
• Various forms of amphetamines, such as speed and crystal meth

Researchers sometimes call cocaine "the perfect heart attack drug." It can cause an increase in blood pressure and heart rate as well as cause atherosclerosis. These effects can occur even among those who consider themselves only recreational users. Most heart attacks from cocaine happen a couple of hours after using the drug.

Lack of Oxygen (Hypoxia)

It's possible to have a heart attack due to a lack of oxygen (hypoxia). This can occur if oxygen levels in the blood decrease because of causes such as carbon monoxide poisoning or the lungs not functioning as they should. In this case, the heart does not receive adequate oxygenated blood, causing heart muscle damage. In turn, a heart attack occurs.

What Raises the Risk of a Heart Attack?

Your risk for a heart attack will vary based on certain risk factors you may have. This will include risk factors you can control, factors you can't control, and health conditions that can increase your risk.

Risk Factors You Can Control

Heart attack risk factors that you can control include:

• Being a smoker
• Having obesity
• Eating a diet high in saturated fat
• Having a lot of stress
• Having high blood pressure
• Having high cholesterol
• Not getting enough physical activity
• Drinking too much alcohol
• Using recreational drugs associated with a risk for a heart attack, such as cocaine

Risk Factors You Can’t Control

Heart attack risk factors that you can't control include:

• Age, as risk rises as a person gets older
• Having a family history of heart disease and heart attacks
• Having gone through menopause
• Males have a higher risk for heart attacks at a younger age, but after menopause, the risk for all sexes is about equal

Conditions That Raise the Risk of Heart Attack

Having certain chronic health conditions can raise your risk for a heart attack, including:

• Both type 1 and type 2 diabetes
• Chronic kidney disease
• Lupus
• Metabolic syndrome
• Rheumatoid arthritis

How to Prevent a Heart Attack

Although you can't get rid of all of your risk factors to avoid a heart attack, making some lifestyle changes can lower your risk:

• Focus on healthy food choices such as vegetables, fruits, whole grains, and lean protein sources. Limit how much sugar and salt you eat.
• Get some physical activity every day. If you're new to regular exercise, even a few minutes of walking each day can be a great start.
• If you smoke, seek support to quit.
• Try to maintain a healthy weight.
• Aim to get enough sleep. Most adults need seven to nine hours of sleep every night.
• Limit how much alcohol you drink or avoid alcohol altogether. Current guidelines say that this means no more than one alcoholic drink per day for women and two drinks per day for men. If you don't drink, continue to avoid alcohol.
• If you have high blood pressure, work with a healthcare provider to help lower it. This includes making lower-sodium food choices.
• Monitor your cholesterol. Aim for an LDL (or "bad" cholesterol) of 70 milligrams per deciliter (mg/dl) or lower while also trying to increase your HDL ("good" cholesterol).
• Do what you can to manage stress.
  

When to Seek Emergency Care

You should seek emergency care anytime you or someone you are with has the signs of a heart attack, which include:

• Chest pain or feeling like there's an elephant on your chest
• Dizziness
• Extreme fatigue
• Indigestion
• Nausea/vomiting
• Pain in the jaw, arms, or upper back
• Shortness of breath
• Sweating a lot

Certain heart attack signs and symptoms can be more common in women, such as extreme fatigue nausea, and sweating both before and during the heart attack.

Summary

Most heart attacks are caused by atherosclerosis or a blockage in one or more arteries leading to the heart. Other conditions like MINOCA can cause a heart attack even if you don't have typical coronary artery disease. Drug misuse and hypoxia also sometimes can lead to a heart attack.

Risk factors that can increase your chances for a heart attack include being older, having a family history of heart disease, smoking, and having high blood pressure. Having certain health conditions, such as diabetes or lupus, also raise your heart attack risk.

Healthy choices like getting enough physical activity, eating nutrient-rich foods, and quitting smoking all go a long way toward preventing a heart attack.