|Definition Of A Heart Attack
A heart attack is where the muscle and tissue of the heart begin to die due to the loss of blood supply. It is also called myocardial infarction.
What Causes A Heart Attack?
A heart attack occurs when blood flow to the heart shuts off due to a blockage in one or more of the coronary arteries supplying it. Without blood and the oxygen and nutrients it carries, the heart muscle begins to die. The sooner medical intervention can restore blood flow (called reperfusion), the more the muscle tissue that will be saved. Once tissue is dead it can never be restored and the part of the heart affected will no longer function. If enough tissue is damaged the person can die because the heart is no longer able to pump. The severity of a heart attack depends on how much muscle is damaged and where in the heart the damage occurs.
How Does A Blockage Occur?
Most people believe that a heart attack is caused by the slow buildup of plaque - that is fatty materials, cholesterol and debris which collect in the coronary arteries and harden over time. This process is called atherosclerosis (image). If unchecked, it eventually narrows and blocks the blood vessels (it is a symptom of coronary heart disease). However scientists now believe atherosclerosis alone is not the main cause of heart attacks. They think most heart attacks occur either when:
A Blood Clot Sticks
A blood clot (techie word thrombus) forms in a blood vessel in the body, it travels through the network veins and ends up sticking to the wall of a coronary artery, which is already thickened with plaque. This sudden blockage stops blood flow. (image)
A Blood Clot Forms
A blood clot forms in the coronary artery itself when plaque breaks from the wall of the artery, causing an open wound (image). Blood platelets rush to the wound and stick to it to form a protective clot, called a thrombus. The clot can enlarge within a matter of minutes and block the artery. This explains why aspirin therapy is sometimes prescribed to people with heart attack risk factors because aspirin helps reduce the stickiness of platelets.
One final cause of blockage is where the coronary artery temporarily spasms narrowing and restricting blood flow. These spasms typically occur in a blocked artery but can occur in normal ones. This is more common in people who take illegal drugs like cocaine or amphetamines.
Why Are Clots More Dangerous?
Heart attacks which are caused by sudden clots are much more lethal than those which occur as the result of years of plaque buildup. This is because a slow blockage allows the body to gradually activate small backup blood vessels called collaterals (image). These bypass vessels serve by offering an alternative route for blood flow. If a blockage occurs suddenly, as is the case with a clot, these coronary collaterals may not have developed enough to take over. According to research published by the European Heart Journal people who have developed collaterals have a 36 percent less chance of dying of a heart attack than those who have not. Coronary collaterals are tiny specialized blood vessels which are invisible until activated. They can expand in width to carry significant amounts of blood flow in cases of blockages. Research shows that people who experience a heart attack and are treated with clot busters (thrombolytic therapy) or coronary angioplasty have better survival rates if their bypass collaterals have been developed.
What Happens When Blood Flow To The Heart Stops?
If blood flow is only partially blocked it causes angina chest pain. If it becomes completely obstructed the heart becomes starved of oxygen and nutrients. This is known as a heart attack. The heart can survive for 20 minutes without blood supply before tissue and muscle starts to die.
How Do Heart Attacks Kill?
A person can die from a heart attack in two ways: Either because so much tissue dies that the heart cannot pump enough to keep the person alive. Or, the heart develops a fatal abnormal heart arrhythmia called ventricular fibrillation. This is where the heart beats abnormally; interruption of the heart beat for only a few seconds is enough to cause sudden death. Heart attacks are the most common cause of ventricular fibrillation, although it can also be caused by congestive heart failure or being electrocuted in an accident.
What Is A Silent Heart Attack?
This is where a heart attack occurs but produces none of the usual heart attack symptoms. Nearly 4 million Americans suffer a silent heart attack every year; many are completely unaware that they have done so. The first sign may be cardiac arrest, where the heart stops pumping and the person collapses. Silent heart attacks are caused in the same way and have the same effects as a regular heart attack. The only difference is that the person experiences no obvious pain or symptoms. If it is a minor attack it may only be discovered later through a routine health screening and exercise stress test.
What Is A STEMI?
There are two main types of a heart attacks: STEMI and NSTEMI. A STEMI is a technical term used to describe a serious type of heart attack. It is caused by an extended period of blockage to a large area of heart muscle. A STEMI causes characteristic changes which can be picked up with an electrocardiogram test (ECG) and blood tests checking for protein markers which occur when the heart is damaged. A NSTEMI is more sneaky because it does not show up on an ECG but it does show up in blood tests. Fortunately NSTEMI’s cause less damage.
What if your heart stops beating? This is called sudden cardiac arrest which can be prompted by heart attacks, but also drowning, choking, electric shock and other traumas. Read about treatment with an automated external defibrillator. For those at risk of SCA, they may consider a home defibrillator.