From http://www.webmd.com/heart-disease/understanding-heart-attack-basics

Understanding Heart Attack: The Basics

What Is a Heart Attack?

The heart requires its own constant supply of oxygen and nutrients, like any muscle

in the body. Two large, branching coronary arteriesdeliver oxygenated blood to the

heart muscle. If one of these arteries or branches becomes blocked suddenly, a

portion of the heart is starved of oxygen, a condition called "cardiac ischemia."

If cardiac ischemia lasts too long, the starved heart tissue dies. This is aheart attack,

otherwise known as a myocardial infarction -- literally, "death of heart muscle."

Most heart attacks occur during several hours -- so never wait to seek help if you

think a heart attack is beginning. In some cases there are no symptoms at all, but

most heart attacks produce some chest pain.

Other signs of a heart attack include shortness of breath, dizziness, faintness,

or nausea. The pain of a severe heart attack has been likened to a giant fist

enclosing and squeezing the heart. If the attack is mild, it may be mistaken

for heartburn. The pain may be constant or intermittent. Also, women are less likely

to experience the classic symptoms of chest pain than men are.

Angina: Early Warning Sign of a Heart Attack

Many heart attack victims are warned of trouble by episodes of angina, which is

chest pain that, like a heart attack, is provoked by ischemia. The difference is mainly

one of degree: With angina, blood flow is restored, pain recedes within minutes, and

the heart is not permanently damaged. With a heart attack, blood flow is critically

reduced or fully blocked, pain lasts longer, and heart muscle dies without prompt

treatment.

About 25% of all heart attacks occur without any previous warning signs. They are

sometimes associated with a phenomenon known as "silent ischemia" -- sporadic

interruptions of blood flow to the heart that, for unknown reasons, are pain-free,

although they may damage the heart tissue. The condition can be detected by ECG

(electrocardiogram) testing. People with diabetes often have silent ischemia.

A quarter of all heart attack victims die before reaching a hospital; others suffer life-

threatening complications while in the hospital. Serious complications include stroke,

persistent heart arrhythmias (irregular heart beats), heart failure, formation of blood

clots in the legs or heart, and aneurysm, or bulging, in a weakened heart chamber.

But those who survive the initial heart attack and are free from major problems a few

hours later stand a better chance of full recovery.

Angina: Early Warning Sign of a Heart Attack continued...

Recovery is always a delicate process, because any heart attack weakens the heart

to some degree. But generally, a normal life can be resumed. Depending on the

severity of a heart attack, a person may experience:

Heart failure , where the heart doesn't pump well enough to meet the body's needs

Arrhythmias or abnormal heart rhythms

Cardiac arrest or sudden cardiac death, where the heart stops beating

Cardiogenic shock, where the heart is so damaged from the heart attack that a person goes

into shock, which may result in damage of other vital organs like the kidneys or liver

Death

What Causes a Heart Attack?

Most heart attacks are the result of coronary artery disease, also known

as atherosclerosis or "hardening of the arteries," a condition that clogs coronary

arteries with fatty, calcified plaques over time. The typical trigger for a heart attack is

often a blood clot that blocks the flow of blood through a coronary artery.

In the early 1980s, researchers confirmed that the trigger for nearly all heart attacks

is not the obstructive plaque itself, but the sudden formation of a blood clot -- like a

scab -- on top of plaque that cuts off blood flow in an already narrowed vessel. This

is called "plaque rupture." Contrary to prior belief, doctors now recognize that the

less severe plaques are the cause of most heart attacks: It's the milder blockages

that rupture and then cause the blood clot to form.

Heart attacks may also be caused by coronary artery spasm, where a heart artery is

temporarily constricted, although this is a fairly rare cause.

New research shows that inflammation also plays a role in the evolution of heart

attacks. It appears that the coronary artery walls become inflamed over time, further

increasing the buildup of fatty plaques.

While the step-by-step process leading to a heart attack is not fully understood,

major risk factors for coronary artery disease are well-known. Some can be

controlled, including high blood pressure, high cholesterol, obesity, smoking, and a

sedentary lifestyle. Stress is also said to raise the risk, and exertion and excitement

can act as triggers for a heart attack.

Other risk factors include having diabetes and having a family history of heart

disease.

WebMD Medical Reference

View Article Sources  

Reviewed by James Beckerman, MD, FACC on February 28, 2015

© 2015 WebMD, LLC. All rights reserved.