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Acute Coronary Syndrome

What are acute coronary syndromes?

Acute coronary syndrome (ACS) is a term used to denote any condition that occurs as a result of reduced blood supply to the heart muscle. The disorders range from a threatened heart attack, also known as unstable angina, to an actual heart attack, called myocardial infarction.

What causes acute coronary syndrome?

The blood vessels that carry blood away from the heart are known as arteries. The heart supplies oxygen-rich blood to the various parts of the body through an artery called aorta. The coronary arteries that branch off from the aorta in turn carry blood to the heart muscle. Any factor that reduces the blood flow to the heart muscle, either due to blood vessel narrowing or blockage, can lead to ACS. One of the most common causes of blood vessel narrowing is atheroma formation. Atheroma refers to deposits called plaques that develop in the wall of the arteries overtime. The plaques comprise an outer hard shell with an inner fatty core. These can impede the blood flow to the heart by narrowing the arterial lumen, that is, the cavity of the arteries. Apart from atheroma, inflammation of the coronary arteries, stab wound to the heart, cocaine abuse, migrating blood clot and surgical complications are a few other conditions causing vessel blockage. Figure 1 illustrates the chambers and different arteries supplying blood to the heart.

What is meant by unstable angina and myocardial infarction?

Unstable angina
Chest pain that occurs as a consequence of reduced blood supply to the heart is termed as angina. Unstable angina occurs as a result of lack of blood flow to the heart muscles. However, the heart muscle is not damaged. Unlike pain with stable angina, which gets better with rest, the symptoms of unstable angina typically occur at rest. The pain persists despite taking medications. Unstable angina is thus equivalent to a threatened heart attack and must be attended to immediately.

Myocardial infarction
A myocardial infarction (MI) is what is commonly known as a heart attack. This occurs as a result of clot formation subsequent to a plaque rupture. The clot can completely block the artery and cut off the blood supply to a portion of the heart muscle. Thus, if not treated at the earliest, it can lead to damage and death of the respective heart muscle. Occasionally, spasm of coronary arteries can also lead to a heart attack.

What are the signs and symptoms of acute coronary syndrome?

The symptoms of ACS are similar to that of a heart attack, and if unattended instantly, it can lead to an actual attack. Signs and symptoms of ACS include:

  • Heart attackSudden discomfort in the chest, which can be burning, squeezing or painful in nature
  • Discomfort or pain radiating to the jaw, shoulder or arm
  • Nausea and/or vomiting
  • Increased sweating
  • Shortness of breath (dyspnoea)
Atypical symptoms include:
  • Feeling of heartburn
  • Pain in the abdomen
  • Severe fatigue and restlessness
What should be done in case of a heart attack?

When in doubt of having a heart attack, urgent medical help should be sought. An early intervention can prevent severe damage. Driving on own should be discouraged. An ambulance can be called for further assistance.

What is cardiopulmonary resuscitation and how should it be performed?

Cardiopulmonary ResuscitationBrain damage can occur secondary to lack of oxygen-rich blood after the heart stops working. To restore the blood circulation, cardiopulmonary resuscitation (CPR) can be very useful. CPR is a procedure for maintaining the functioning of the heart and restoring the breathing function of the lungs.
The American Heart Association recommends the following while performing a CPR:

  • If you are not trained in CPR, then provide about 100 chest compressions per minute until the arrival of paramedics
  • If you are trained in CPR and confident, begin with 30 chest compressions before checking the airways and initiating rescue breaths
  • If you are trained and not confident enough, provide about 100 chest compressions per minute until the arrival of paramedics

Another form of resuscitation that is gaining popularity is cardiocerebral resuscitation, in which recommends on continuous chest compressions without mouth-to-mouth breathing.

Who is at risk of having a heart attack?

SmokingRisk factors of a heart attack are similar to that of any other heart disease. These are classified into modifiable and non-modifiable risk factors. Modifiable risk factors include:

  • Smoking
  • Hypertension
  • Obesity
  • High cholesterol
  • Lack of physical activity
Non-modifiable risk factors include:
  • Age (over 45 years for men and 55 for women)
  • A family history of heart disease
  • Preeclampsia (pregnancy-induced hypertension)

How is acute coronary syndrome diagnosed?

It is important to differentiate the pain caused by ACS from the pain due to other causes. Various tests that help in appropriate diagnosis have been discussed below:

Electrocardiogram (ECG/EKG)

ECG is usually the first investigation performed if a heart disease is suspected. Electrodes attached to the body transmit electrical impulses, which get recorded as waves on the ECG paper. A dead heart tissue lacks electrical activity and hence an ECG can depict signs of current or previous heart attack.

Blood sample

An injury to the heart tissue can lead to leakage of certain enzymes of the heart, which can be detected in the blood. Hence, a blood sample is usually collected for testing the enzymes. A positive test warrants hospitalisation.


An echocardiogram is a procedure that principally uses sound waves to create a moving image of the heart. Sound waves are transmitted to the heart by a device called transducer. These waves are reflected back as electrical impulses, which eventually get converted into heart images. An echocardiogram can detect areas of damaged heart tissue.

Chest x-ray

Chest x-ray aids in determining the size and shape of the heart and the arteries.

Nuclear scan

Nuclear scans are performed using radioactive materials. These radioactive materials are injected into the blood stream and traced using special cameras as they flow to organs such as the heart and lungs. Areas with impeded or reduced flow appear as dark spots.

Computerised tomography (CT) angiogram

A CT angiogram helps in detecting any narrowing or blockage of the coronary arteries. A radioactive dye is injected and multiple images of the arteries are taken with the help of a CT scanner, which are then sent to the doctor for review.

Angiography (Coronary angiogram/ cardiac catheterisation)

It is an invasive procedure that can help in the diagnosis as well as treatment of an arterial block. Coronary arteries are accessed via the blood vessels (veins) in the legs, with the help of a long thin catheter. A liquid dye is injected into the coronary arteries, which then appear on the x-rays and detects any blockage. The same catheter can be used to widen the blocked area with the help of small balloons; this procedure is termed angioplasty.

How is acute coronary syndrome treated?

Treatment in the first 12 hours

The treatment of ACS depends on the symptoms and the extent of arterial blockage. The aim of the treatment is to relieve the pain and improve the circulation of blood through the coronary arteries.

Medical management

Oxygen therapy
Oxygen therapy provides extra oxygen to the lungs and helps in patients in whom oxygen delivery is hampered. The oxygen is contained in a metal cylinder and delivered with the help of a nasal cannula, mask or a tube inserted into the trachea (windpipe).

Blood thinning treatment

AsprinAspirin therapy
Aspirin is usually the first medicine to be given in patients with suspected acute coronary event. Aspirin prevents clotting of blood and eases the flow of blood through the narrowed arteries. Chewing the tablet aids in better absorption. Once ACS is confirmed, the patient is usually put on lifelong treatment with aspirin.

Aspirin and clopidogrel
A combination of aspirin and clopidogrel is recommended in patients with:

  • Change in rhythm of the heart
  • Raised cardiac enzymes (troponin) levels

Glycoprotein llb/lla receptor antagonist
Patients who are at increased risk of having a heart attack or undergoing a procedure called angioplasty (percutaneous coronary intervention)are usually prescribed glycoprotein llb/lla receptor antagonist. These drugs are given intravenously (directly inside the veins),which helps in widening the blocked arteries.


Anticoagulants are a class of drug that prevents clotting of blood and are prescribed to patients who have heart rhythm changes. Examples of commonly used anticoagulants include low-molecular-weight heparin and fondaparinux. These drugs are usually given for 8 days, or until discharge, or if the patient is undergoing heart surgeries.

Beta blockers

Beta blockers are a class of drug that helps in reducing the blood pressure, heart rate and workload of the heart. They also help in alleviating chest pain and improve the blood flow through the heart. During a heart attack, they can also reduce the risk of damage to the heart tissues.

Cardiac monitoringCardiac monitoring

Continuous heart rhythm monitoring is done to enable early detection of abnormalities.

Insulin therapy

Patients with a history of diabetes presenting with a heart attack, or those with increased levels of blood sugar are put on insulin for blood sugar control.

Invasive management

Angiography and Revascularisation

Patients in whom invasive procedures are considered include:

  • Patients with non-ST elevation acute coronary syndromes at medium to high risk of early recurrent cardiovascular events
  • Patients with ST elevation acute coronary syndromes treated with thrombolytic therapy

After the first 12 hours have passed, the coronary arteries are unblocked using coronary angiography and revascularisation. The range of procedures that aid in unblocking a narrowed artery is termed as revascularisation.

Primary angioplasty (primary percutaneous coronary intervention)

This procedure is basically performed to widen a blocked or narrowed artery. A small tube called catheter with a deflated balloon at its tip is inserted in to the coronary artery via an artery in the groin or arm. X-rays are used to gain access to the coronary artery and the blocked area within. Upon reaching the narrowed segment, the balloon is inflated, which compresses the fatty deposits, thereby widening the artery. A small steel mesh, called stent, is left in place to keep the artery open. Glycoprotein llb/lla receptor antagonists are administered along with the procedure to reduce pain and decrease the formation of clots.

Rescue angioplasty (rescue percutaneous coronary intervention)

In a patient presenting with acute coronary syndrome, if thrombolytic therapy fails to reperfuse the infarcted myocardium within 6 hours of symptom onset, a rescue angioplasty is performed.

Bypass heart surgery (coronary artery bypass graft/CABG)

Bypass heart surgery is an alternative surgical procedure to treat a heart attack. It involves grafting or connecting a healthy vessel (artery or vein) to the blocked coronary artery to bypass the blockade, hence, providing an alternative route for blood to go around a blocked coronary artery.

Thrombolytic therapy

Also known as ‘clot busters’, thrombolytics are the drugs that help in dissolving clots and clearing the block. Thrombolytics need to be administered as soon as possible if angioplasty is not performed in the first 90 minutes after diagnosis; early treatment minimises the damage to the heart muscle and improves survival rates.

Treatment beyond the first 12 hours

Surgical management

Cardiac surgery
Patients presenting with rupture of cardiac muscle in heart attack should undergo corrective surgery within 24 to 48 hours.

What are the common medicines prescribed after a heart attack?

Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs)

These drugs help in reducing blood pressure and improve the pumping capacity of the heart. They are generally prescribed after an attack to prevent repeat attacks. ACE inhibitors are initiated within the first 36 hours in case of a

  • Heart attack
  • Unstable angina or
  • Heart tissue damage

ARBs are generally prescribed in case of reduced tolerance to ACE inhibitors or in conditions where the left side of the heart is compromised.


Aspirin tablet can be either chewed or swallowed. Long-term aspirin therapy with a daily dose of 75 to 150mg recommended.
Clopidogrel is prescribed for a period of 1 to 3 months by the physician depending upon the nature of ACS in

  • Patients with unstable angina scheduled for an invasive procedure
  • Patients with drug-eluting stents to prevent the formation of clots
  • Patients with heart attack undergoing angioplasty (percutaneous coronary intervention) or thrombolytic therapy
Beta blockers and anti-anginal therapy

Patients are put on long-term beta blockers if they have a history of heart attack, unstable angina or damage to the heart muscles. Nitrates are given to relieve the pain associated with angina and heart failure.


Eplerenone are aldosterone receptor antagonists and are prescribed to patients with diabetes or heart failure after a heart attack.

Cholesterol-lowering drugs

Long-term statin therapy is given to patients after discharge to reduce the cholesterol levels.

Cardiac rehabilitation

Cardiac rehabilitation is a set of programmes specially designed for patients with heart disease to enable them cope better with the condition. The rehabilitation team consists of highly qualified professionals who provide solutions for improving the health and well-being of the individual. The programme mainly focuses on:

  • Exercise
  • Education
  • Counselling
  • Training to prevent a future episode of ACS

Cardiac rehabilitation or secondary prevention is recommended in patients with multiple modifiable risk factors and/or patients with moderate to high risk for ACS. They are provided with supervised exercise training, which is known to improve exercise tolerance without increasing cardiovascular complications. Education about their heart condition and counselling helps to further reduce recurrent of cardiovascular events, cope with stress of adjusting to a new healthy lifestyle and improve psychosocial well-being. Cardiac rehabilitation can also facilitate in faster recovery to resuming work.


Eplerenone are aldosterone receptor antagonists and are prescribed to patients with diabetes or heart failure after a heart attack.

Cholesterol-lowering drugs

Long-term statin therapy is given to patients after discharge to reduce the cholesterol levels.

What are the complications associated with ACS?

Complications of ACS include:

  • Pulmonary oedema: Fluid collection in the lungs leading to dyspnoea (shortness of breath)
  • Cardiogenic shock: A sudden drop in the blood pressure along with reduced blood flow
  • Heart muscle rupture
  • Long-lasting pain
How can you prevent ACS?

ACS can be prevented by adopting a heart healthy lifestyle.

Quit SmokingQuit smoking

Smoking can adversely affect the heart and blood vessels. Smoking is an independent risk factor for the development of heart disease. Smoking damages the function of the heart and blood vessels and accelerates the progression of atherosclerosis (a condition where a deposit called plaque blocks the arteries and causes narrowing of the arterial cavity). Passive or second-hand smoking can also be detrimental for the health of the arteries and the heart and can increase the risk of heart attack substantially.
Quitting smoking at any age has huge health benefits. People who quit before the age of 50 or after 60 have decreased risk of cardiovascular events.

Follow a healthy dietFollow a healthy diet

Patients at risk of ACS and those after an episode of ACS are advised to restrict their salt and fat intake. This helps in keeping the blood pressure and cholesterol in control. A wholesome, low-fat diet that includes fruits, vegetables and grains is recommended.

Control Body WeightControl body weight

Obesity is a risk factor for coronary heart disease and heart attack. Moderate exercise for around 30 minutes a day can promote weight loss and help in controlling the levels of sugar, cholesterol and blood pressure. Regular exercise also helps in improving the blood flow to the heart and increases stamina. However, it is advisable to consult a doctor before initiating any exercise programme.

Periodic blood tests to assess cholesterol levels

Cholesterol levels need to be checked at frequent intervals. The recommended lipid levels are:

Total cholesterol
<200 mg/dL
Low-density lipoprotein cholesterol
<130 mg/dL for individuals at low risk
<100 mg/dL in people with moderate risk
<70 mg/dL for those with high risk
High-density lipoprotein cholesterol
>40 mg/dL for men
>50 mg/dL for women

Diet changes and medications are prescribed in case of increased lipid levels.

Maintain normal blood pressure

Blood pressure should be checked every 2 years and more frequently if already on treatment for hypertension and/or heart disease. The normal blood pressure is <120/80 (systolic/diastolic) millimetres of mercury (mm Hg).

Manage Stress LevelsManage stress levels

Reduction of stress levels decreases the risk of heart attack in individuals. Lifestyle changes should be considered to manage stress levels efficiently.

Moderate consumption of alcohol

Alcohol should be consumed in moderation as excessive drinking can increase the blood pressure.

How is life after an episode of ACS?
  • Patients after an attack can have a better quality of life if prompt treatment is administered
  • Earlier the treatment better is the chances of recovery
  • Regular follow-ups with the doctor are essential
  • Patients who do not have chest pain can resume normal daily activities within a few weeks
  • If the condition is associated with complications, patients should refrain from driving till the symptoms are stabilised
  • Professional counselling and health groups can help in coping with post-attack anxiety; medications can be prescribed if required

Source: AstraZeneca (