Acute Coronary Syndrome

Acute coronary syndrome is a life-threatening emergency that occurs when blood flow to the heart suddenly decreases or stops completely. This umbrella term includes heart attacks and unstable angina, all of which require immediate medical attention to prevent permanent heart damage or death.

Table of contents

• What is acute coronary syndrome?
• Types of acute coronary syndrome
• Symptoms
• Causes and risk factors
• How doctors diagnose acute coronary syndrome
• Treatment options
• Prevention and lifestyle changes
• What to expect after acute coronary syndrome

What is acute coronary syndrome?

Acute coronary syndrome (ACS) refers to a group of conditions that involve sudden, reduced blood flow to your heart^[1]. When blood cannot flow properly to the heart muscle, the heart cannot get enough oxygen to function as it should. This can result in irreversible damage to your heart or even sudden cardiac death^[1].

The term acute means the condition comes on suddenly. Coronary refers to the arteries that supply blood to the heart. Syndrome indicates that several related conditions are grouped together under this name^[2].

ACS is always a medical emergency that needs prompt treatment^[3]. If you experience symptoms of acute coronary syndrome, call emergency services immediately. Do not wait or try to drive yourself to the hospital^[1].

• Heart
• Coronary arteries

Types of acute coronary syndrome

There are three types of acute coronary syndrome, which differ based on how severe the blockage is and how much damage has occurred to the heart^[1].

Unstable angina is chest discomfort that is different, more severe, or happens more often than usual. Unlike stable angina, it occurs at times you would not expect, even at rest. It means there is reduced blood flow in a coronary artery, but no heart damage has occurred yet^[1].

Non-ST-segment elevation myocardial infarction (NSTEMI) is a heart attack that results from a partial blockage in a coronary artery. This type of heart attack can lead to heart damage. The blockage may be partial or temporary, so the damage to the heart is relatively small^[1].

ST-segment elevation myocardial infarction (STEMI) is a heart attack due to a complete blockage in a coronary artery. This is the most severe type of acute coronary syndrome. Your heart could be severely damaged, with the muscle starting to die, or you could die without quick treatment^[1].

It is possible for unstable angina to quickly turn into a heart attack, and for an NSTEMI to turn into a STEMI^[1].

Symptoms

The symptoms of acute coronary syndrome usually start suddenly and can occur without warning, even while you are resting^[1].

The most common symptom is chest pain or discomfort. This can feel like pain, aching, burning, pressure, tightness, squeezing, or crushing in the center of your chest^[1][2]. This chest pain is also called angina.

Pain may spread from your chest to other parts of the body. These areas include the shoulders, arms, upper abdomen, back, neck, or jaw^[1][2].

Other symptoms you might experience include^[1][2]:

• Shortness of breath
• Dizziness or fainting
• Sudden, excessive sweating
• Fatigue or weakness
• Racing or pounding heart
• Nausea or vomiting
• Upset stomach that may feel like indigestion or heartburn
• Anxiety

It is not always easy to tell if chest pain comes from your heart or something else, like acid reflux. Many people with acute coronary syndromes present with symptoms other than chest pain, particularly women, older people, and people with diabetes^[5]. Women and older adults often experience symptoms such as shortness of breath, nausea, or extreme fatigue, although chest pain is still common for them^[7].

The classic presentation is not always seen, and the symptoms can be very vague and subtle. Some people complain mainly of difficulty breathing, lightheadedness, isolated jaw or left arm pain, nausea, stomach pain, sweating, and weakness^[3].

That is why you should always seek medical care immediately for sudden chest pain. Do not try to guess the cause or wait it out. If it is acute coronary syndrome, every minute can make the difference between surviving and not^[1].

Causes and risk factors

A blood clot in your coronary artery causes acute coronary syndrome. This is generally due to cholesterol plaque rupturing inside your artery, but it can happen due to blood clots coming from other sources^[1]. Plaque is a fatty substance made up of cholesterol, fat, cells, and other materials^[7].

The clot partly or completely blocks the space where blood can flow. This means your heart cannot get enough blood. Severe blockages can damage your heart muscle or even be fatal^[1].

You may develop acute coronary syndrome if you are living with coronary artery disease. This means you have cholesterol plaque buildup in your arteries. The plaque gradually narrows your arteries over many years^[1]. This may cause stable angina, or chest discomfort that comes and goes in predictable patterns, usually when you exercise or are physically active^[1].

Things can quickly change if the surface of that plaque wears away (called plaque erosion) or breaks open (called plaque rupture). When the plaque ruptures, it triggers the formation of a blood clot that can rapidly and severely narrow or block the artery^[1].

Sometimes acute coronary syndrome can be secondary to vasospasm, which is a sudden tightening of the blood vessel, with or without underlying plaque buildup^[3]. Cocaine abuse can also lead to vasospasm^[3].

Several risk factors can increase your chances of developing acute coronary syndrome. Common risk factors include^[3]:

• Smoking
• High blood pressure
• Diabetes
• High cholesterol
• Being male
• Physical inactivity
• Obesity
• Poor nutrition

A family history of early heart attack (before age 55 in men or before age 65 in women) is also a high-risk factor^[3].

How doctors diagnose acute coronary syndrome

Acute coronary syndrome is diagnosed at a hospital as an emergency. The healthcare team will run tests to check your heart and determine the cause of your symptoms^[9].

Your healthcare provider will perform a physical examination, listen to your chest with a stethoscope, and ask about your symptoms and medical history^[1][7].

The main tests used to diagnose acute coronary syndrome include:

Electrocardiogram (ECG or EKG) is usually the first test your provider will run. This quick test shows how the heart is beating. Sticky patches with sensors attach to the chest and sometimes to the arms or legs. Changes in the heartbeat may mean the heart is not working as it should. Your healthcare professional can look for patterns in the heartbeat to find the general location of any blockages^[9]. Guidelines recommend that people receive this test within 10 minutes of arriving at the emergency department^[6].

A distinctive pattern on the ECG (a rise in the ST segment, which is normally flat) usually means one of the main coronary arteries is completely blocked, indicating a STEMI. About 70% of people with acute coronary syndrome have an artery that is not completely blocked, so their ECGs show different patterns, often involving dips instead of rises in the ST segment^[6].

Blood tests are done to check for certain heart proteins that slowly leak into the blood after heart damage from a heart attack. A troponin blood test can indicate if your heart cells have been damaged and confirm if you are having a heart attack^[7][9]. Troponin levels are generally elevated within 2 to 4 hours of symptom onset but may not become abnormal for up to 12 hours. Troponin elevations may persist for more than 14 days^[6].

Your healthcare team looks at your symptoms and test results to diagnose acute coronary syndrome. This information also helps classify your condition as a heart attack or unstable angina^[9].

Other tests may be done to determine the best treatment or rule out other possible causes of symptoms. These include^[7][9]:

Coronary angiogram looks for blockages in the heart arteries. A doctor places a thin, flexible tube called a catheter into a blood vessel, usually in the groin or wrist, and guides it to the heart. Dye flows through the tube to arteries in the heart. The dye helps the arteries show up more clearly on images taken during the test. Some heart treatments can be done during this test^[9].

Echocardiogram uses sound waves to create pictures of the beating heart. This test shows how blood flows through the heart and heart valves. An echocardiogram can show whether the heart is pumping properly and can help identify some types of heart problems^[7][9].

While you are in the hospital, you may undergo additional tests to evaluate your heart, including exercise stress test, nuclear stress test, or stress echocardiography^[7].

Treatment options

The goals of treatment are to relieve symptoms, restore blood flow to the heart, and prevent complications^[10]. Your provider may use medicines, surgery, or other procedures to treat your symptoms and restore blood flow to your heart. Your treatment depends on your condition and the amount of blockage in your arteries^[7].

Medications

Your provider may give you one or more types of medicine^[7][13]:

• Aspirin and other antiplatelet drugs (such as clopidogrel, prasugrel, or ticagrelor) help prevent blood clots from forming
• Beta-blockers reduce the heart’s workload and help stabilize the heart
• Statins help lower cholesterol levels
• Blood thinners (anticoagulants like heparin or bivalirudin) help prevent clots from getting larger
• Clot-dissolving medicines (thrombolytics or fibrinolytics) can break up existing blood clots
• Angiotensin-converting enzyme (ACE) inhibitors help lower blood pressure and reduce strain on the heart
• Nitroglycerin helps relieve chest pain by widening blood vessels

Chest pain can be treated with nitroglycerin or sometimes morphine. Nitroglycerin is preferable to morphine, which should be used carefully^[15].

Procedures and surgery

Rapid restoration of blood flow with primary percutaneous coronary intervention (PCI) is the goal with either clinical presentation^[10]. This is the preferred treatment whenever possible.

Angioplasty and stent placement is a procedure that opens the clogged artery using a long, thin tube called a catheter. The tube is placed in the artery and a small deflated balloon at the end of it is inflated inside the artery to open it up. Your doctor may also insert a wire tube called a stent to keep the artery open^[7].

Coronary artery bypass surgery is surgery to route the blood around the artery that is blocked^[7].

If percutaneous coronary intervention cannot be performed rapidly, patients with STEMI can be treated with fibrinolytic therapy (clot-dissolving drugs). However, fibrinolysis is not recommended in patients with NSTEMI or unstable angina, as it can worsen outcomes for these conditions^[10].

Some patients with severe low blood pressure or other signs of shock may require the insertion of an intra-aortic balloon pump to help the heart pump blood^[13].

Prevention and lifestyle changes

Secondary prevention after acute coronary syndrome should be offered to every patient and should start as early as possible after the event. It has been shown to both increase quality of life and decrease morbidity and mortality^[21].

The most important aspects of prevention focus on reducing risk factors for coronary artery disease^[10]:

Smoking cessation is critical. Smoking, combined with a lack of exercise or dietary restraint, for even 6 months after an acute coronary syndrome incident, increases nearly 4-fold the incidence of heart attack, stroke, and death^[20].

Regular exercise is essential. At least a half hour of moderate exercise 5 times per week is recommended for patients who have been cleared for exercise^[20]. Lack of exercise, including excessive sitting, increases cardiac illness and death^[20].

Healthy diet should be maintained. Improvements in diet can help prevent recurrence of acute coronary syndrome^[20].

Managing other health conditions is important. This includes controlling high blood pressure, high cholesterol, and diabetes through medication and lifestyle changes^[10].

Maintaining a healthy weight and reducing obesity can lower your risk^[3].

Early, individualized education leads to better self-care and greater satisfaction with that care. Family and health care social support increases the perceived benefit, which improves adherence with self-care and thereby improves outcomes^[20].

What to expect after acute coronary syndrome

How well you do after acute coronary syndrome depends on several factors^[7]:

• How quickly you get treatment
• The number of arteries that are blocked and how bad the blockage is
• Whether or not your heart has been damaged, as well as the extent and location of the damage

In general, the quicker your artery gets unblocked, the less damage you will have to your heart^[7].

Most individuals will adhere to self-care for a month after they are given an acute coronary syndrome diagnosis, but adherence drops at about 6 months after discharge from the hospital^[20]. Regular monitoring and education on the benefits of diet and exercise can improve patient adherence to healthy behaviors^[20].

Patients discharged after acute coronary syndrome should be directed to care pathways appropriate to their individual risk level to ensure appropriate patient management^[21]. Post-event care should be closely coordinated with your cardiologist and based on a comprehensive secondary prevention strategy to prevent recurrence, illness, and death^[10].

Engaging and educating the patient is a key component of acute coronary syndrome care and should take place throughout the patient journey, from admission to hospital discharge and cardiac rehabilitation^[21].

Adherence to medical treatment is a priority. Long-term adherence to self-care depends on a patient’s beliefs, disease knowledge, overall ability to function, emotions (such as anxiety and depression), and outside influences (such as social and health care networks)^[20].