Heart attack is the death of a segment of heart muscle caused by the loss of blood supply.
The blood supply is usually lost because a coronary artery, one that supplies blood to the heart muscle, has a blood clot, a blockage (coronary thrombosis). If some of the heart muscle dies, the patient experiences chest pain and electrical instability of the heart muscle tissue.
Other terms used for a heart attack include myocardial infarction, cardiac infarction and coronary thrombosis (Infarction = the process whereby an area of dead tissue is caused by a loss of blood supply).
Blood supply to the heart can also be undermined if the artery suddenly narrows, as in a spasm.
According to the American Heart Association:
The animation above shows how plaque buildup, or a coronary artery spasm, can eventually lead to a heart attack, and how a heart attack can occur when blood flow in a coronary artery is blocked.
- During a heart attack the heart muscle that loses its blood supply starts to suffer injury.
- How much damage occurs depends on the size of the area that is supplied by the blocked artery, as well as the lapse in time between injury and treatment.
- The damaged heart muscle heals by forming scar tissue. The healing process may take several weeks.
- Despite severe injury to a part of the heart, the rest of the organ carries on working.
- However, as part of the heart has been damaged, it will probably be weaker and will not pump as much blood as it used to.
- With the right treatment and lifestyle changes, further damage can be prevented or limited.
Symptoms of a heart attack
The following are signs and symptoms for diagnosing a heart attack:
- Chest discomfort, mild pain - a study published in JAMA Internal Medicine reported that one fifth of younger women having a heart attack experience no chest pain. The researchers defined younger women as those aged up to 55 years.
- Crushing chest pain (see comment above on "mild pain").
- Dyspnea (shortness of breath).
- Face seems gray.
- A feeling of terror that your life is coming to its end.
- Feeling really awful (general feeling).
- The patient is clammy and sweaty.
If you experience these symptoms, or witness another person with them, call the emergency services immediately. In the United Kingdom the telephone number is 999, in the USA and Canada it is 911, Australia 000, and New Zealand 111.
When somebody has a heart attack, they usually feel pain in their chest first. The pain then spreads to the neck, jaw, ears, arms, and wrists. The pain may also make its way into the shoulder blades, the back, and the abdomen.
Changing position, resting or lying down does not alleviate the pain.
It is typically a constant pain, but it may sometimes come and go. Patients describe the pain as one of pressure, like a clamp squeezing inside your chest. The pain can last from a few minutes to many hours.
Silent heart attack
People with diabetes, and/or those over the age of 75 may experience a "silent heart attack", one with no pain at all. Painless heart attacks are more common among women than men.
Studies indicate that about 1 in every 5 mild heart attacks are not diagnosed. If this is the case, there are many people who are suffering progressive heart muscle damage because it is not being treated.
Heart attack warning signs in women
Image credit: U.S. Department of Health and Human Services Office on Women's Health
Causes of a heart attack
The following are possible factors associated with increased risk of heart attack.
1) AgeAge is the largest risk factor for heart attacks. When a man is over 45 years, and a woman is over 55 years of age, their risk of having a heart attack starts to rise significantly.
Age is said to be the biggest risk factor for heart attacks.
Scientists from the University of Copenhagen, Denmark, found that the visible physical signs of aging, such as the accumulation of fatty deposits on the eyelids and baldness are associated with a higher risk of developing heart disease and having a heart attack.
Senior researcher, Anne Tybjaerg-Hansen, said "The visible signs of aging reflect physiologic or biological age, not chronological age, and are independent of chronological age."
The researchers found that a receding hairline, baldness, earlobe crease and xanthelasmata (fatty deposits around the eyelids) increased heart attack risk by 57% and ischemic heart disease by 39%.
They presented their findings at the American Heart Association's Scientific Sessions 2012 in Los Angeles.
Angina is an illness where not enough oxygen is reaching the patient's heart. This raises the risk of a heart attack. In some cases a diagnosis of angina was wrong - it could have been a mild heart attack instead. The main difference between a heart attack and angina is that the patient with angina will feel better about 15 to 30 minutes after taking medication, while the heart attack patient won't.
3) Blood cholesterol levels
If a person's blood cholesterol levels are high, he/she runs a higher risk of developing blood clots in the arteries. Blood clots can block the supply of blood to the heart muscle, causing a heart attack.
4) Living near major highways
Heart attack survivors who live near major highways have a 27% higher risk of another heart attack within a decade compared to survivors who live further away, researchers from the Beth Israel Deaconess Medical Center reported in the journal Circulation (May 2012 issue).
The researchers compared heart attack survivors who lived within 328 feet (100 meters) or less from a major highway to their counterparts who lived at least 3,280 feet (1,000 meters) away.
People with diabetes have a higher risk of developing several diseases and conditions, many of them contribute to a higher risk of heart attack.
A person who consumes large quantities of, for example, animal fats, or saturated fats, will eventually have a higher risk of having a heart attack.
7) Gut bacteria can cause heart problems
The action of bacteria in the intestines on certain compounds contained in digested food, especially lecithin, is linked to an increased risk of heart attack and stroke, researchers from the Cleveland Clinic, Ohio, USA, reported in NEJM (New England Journal of Medicine (April 2013 issue). Eggs are rich in lecithin.
A growing number of studies have been suggesting a link between the action of gut bacteria and heart attack and stroke risk.
In another study, published in Nature Medicine (April 2013 issue), scientists explained that L-carnitine, a compound added to energy drinks and found in red meat, may increase heart risk, because gut bacteria digest it and produce TMAO (trimethylamine-N-oxide). TMAO is a metabolite that experts believe clogs up the arteries.
You can inherit a higher risk of heart attack from your parents, and/or their parents. A person whose sibling died of a heart attack has a higher risk of suffering a fatal heart attack, a report published in the Journal of the American Heart Association informed.
9) Heart surgery
Patients who have had heart surgery have a higher risk of having a heart attack.
10) Hypertension (high blood pressure)
This could be due to lack of physical activity, overweight/obesity, diabetes, genes, and some other factors.
11) Obesity, overweight
As more and more people are overweight, especially children, experts believe heart attacks will become more common in future (if the overweight children become overweight adults).
12) Physical inactivity
People who do not exercise have a much higher risk of having a heart attack, compared to people who exercise regularly.
13) Previous heart attack
Anybody who has already had a heart attack is more likely to have another one, compared to other people.
People who smoke heavily or regularly run a much higher risk of heart attack, compared to people who never smoked and those who gave up. Smoking regularly means smoking every day.
15) Being HIV positive
People who are HIV positive have a 50% higher risk of heart attack, researchers reported in JAMA Internal Medicine (March 2013 issue)
16) Work stress
If you have a very demanding job, not much freedom to make decisions, i.e. a job with a lot of stress, your risk of heart attack is higher-than-normal, researchers from University College London reported in The Lancet.
Shift work was also linked to a higher risk of heart attack, according to an analysis that reviewed studies covering over two million people.
17) Calcium supplements
A study published in the journal Heart (May 2012 issue), which analyzed data on nearly 24,000 people over a ten-year period, suggested that taking calcium supplements may raise the risk of heart attack.
Diagnosis of heart attacks
Any doctor, nurse, or health care professional, will send a patient straight to hospital if he/she suspects the person may have a heart attack. In hospital several tests may be done:
An ECG is a medical device that monitors the electrical activity of the heart muscles. Our hearts produce a small electric signal at every beat. A heart specialist (cardiologist) can use this device to see how well the heart is functioning, whether there is any damage to the heart muscle, or abnormalities with the heart rhythm. A doctor can tell, when checking the data coming from the ECG, whether the patient has had a heart attack recently, or even earlier.
Cardiac enzyme tests
When a person has a heart attack some enzymes make their way into the bloodstream. A blood test can detect these enzymes. Usually, enzyme blood levels are checked regularly over a few days.
This can be useful to see if the heart has any swelling.
On the next page we look at the available treatments for heart attack sufferers, including treatments carried out during a heart attack and those used when the patient is in recovery.