Heart Attack (Myocardial Infarction)

Heart attack, also known as a myocardial infarction, is one of the leading causes of death in many parts of the world. In Singapore, it is the number two killer after cancer.

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What is a heart attack?

A heart attack occurs when blood flow to part of the heart is blocked, causing poor supply of oxygen to the heart muscles. If not treated promptly, the affected heart tissue dies.

Some people have chest pains when a heart attack happens, while others have no symptoms at all. It is important to be aware of the risks of a heart attack because most of them are preventable.

Chest pain does not always mean a person is suffering from a heart attack. It can be a sign that there is a problem in another body system, such as in the lungs or gastrointestinal tract.

Before a heart attack, most victims experience episodes of angina (chest pain) that, like a heart attack, are triggered by blockage of blood flow to the heart (ischaemia). With angina, blood flow is quickly restored, pain recedes within minutes, and the heart is not permanently damaged.

However, a third of all heart attacks occur without warning signs. Victims suffer from sporadic interruptions of blood flow to the heart that, for unknown reasons, are pain-free, although they gradually damage the heart tissue. This condition is known as silent ischaemia and can be detected by an electrocardiogram (ECG).

Related: Chest Pains  

Heart Attack Causes and Risk Factors 

The most common cause of a heart attack is atherosclerosis (narrowing of the artery due to build-up of cholesterol) of one or more arteries that supply the heart. The heart needs a steady supply of oxygen to function well. When there is disruption of the blood flow due to blockage or narrowing of the artery, oxygen supply to the heart is compromised. If the blood flow is not restored, the heart cells are injured and eventually die.

Risk factors for a heart attack include the following:
High level of lipids in blood, especially low-density lipoprotein (LDL) cholesterol
Too much stress
Inactive lifestyle
Tobacco smoking
Excessive alcohol consumption
Family history of heart attack
High levels of certain proteins in the body, such as C-reactive protein, fibrinogen and homocysteine

In general, men have a higher risk of heart attack than women. However, women have increased risk of heart attack after menopause.


Signs of a Heart Attack



Myocardial infarction symptoms include the following:
Prolonged crushing, squeezing or burning pain in the centre of the chest
Pain that radiates from the chest area to the neck, arms, shoulders or the jaw
Shortness of breath
Dizziness
Nausea
Chills and sweating
Weak pulse
Cold and clammy skin, grey pallor


Heart Attack Complications 

Damage to the heart caused by a heart attack leads to serious consequences like:
Heart failure
Abnormal heartbeats which can be fatal
Weakening of heart muscles with the potential risk of heart rupture
Damage to the heart valves

Heart Attack Treatment   

If You Are Outside of a Hospital
Immediately call for an ambulance
Take an aspirin tablet if available

Once in a Hospital
Pain relief will be provided
All the relevant tests will be carried out once you are stabilised, including:
An ECG — a specific pattern will arise from the tracings of the electrical activity of the heart 
Blood tests — the level of cardiac enzymes will rise above normal in the event of a myocardial infarction, due to injury/death of the heart muscle cells

The degree of abnormality in the ECG and the level of cardiac enzymes can be used to reveal what type of myocardial infarction you have suffered, and the extent of the heart damage caused by the attack.

If the flow of blood (and therefore oxygen) is restored as soon as possible (within a few hours) to the heart muscles that were affected during a heart attack, much of the muscle cells will survive. This is the reason for prompt treatment. 

There are two types of myocardial infarction treatment that may be given:

Thrombolysis 

This method uses medications that are given intravenously to break down any clots causing the heart attack, and in doing so, restore the blood flow to the damaged heart muscles. If administered quickly, this can work in 50 percent to 70 percent of patients, reducing fatalities. 

Thrombolysis carries with it risks, including increased risks of haemorrhage (bleeding). Therefore, it will be unsuitable for patients who have had a recent major bleed, stroke, uncontrolled hypertension, recent surgery, or bleeding disorders. 

Angioplasty 

A thin wire with a balloon at the end will be passed into the blocked coronary artery via a vessel in the groin or arm. The balloon is then inflated inside the blocked/narrowed artery to widen it, allowing blood to flow again. A stent may be placed as well to keep the vessel open.

Because of the increased risks of fatal heart arrythmias (irregular heartbeats) developing after a heart attack, you may be transferred to a coronary care unit (CCU) for closer monitoring and intervention if required. ECGs and blood tests will be carried out over the course of your stay to monitor your progress.

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Heart Attack (Myocardial Infarction)

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