What Does Angina Look Like on an ECG?

Angina is a clinical syndrome characterized by chest discomfort or pressure caused by a transient lack of blood supply, but no damage to heart muscles. Reduced blood flow manifests as chest pain, causing identifiable changes on the ECG. 

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Exertion or psychological stress causes angina, but it is relieved on rest or by sublingual nitroglycerin. Symptoms, along with an ECG and myocardial imaging, can aid in diagnosing it. The two diagnostic features on ECG are:-

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• ST depression

• T-wave inversion 

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Doctors can thus evaluate the severity of ischemia, determine the need for further tests, such as angiography, and plan treatments accordingly. Angiography, medications, lifestyle changes, and surgical interventions, such as revascularization, also form part of the treatment plan. Timely interpretation of ECG ensures improved outcomes and quality care for patients. In this blog, we explore how angina is depicted on the ECG.

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How does angina differ from a heart attack?

Angina and heart attack are sequelae of coronary artery disease, differing in the extent of damage caused to the heart. A heart attack shows complete obstruction of blood flow to a part, whereas in angina, there is a temporary reduction in blood flow to the muscles.

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Additionally, rest or medication (such as nitroglycerin) can provide relief within a few minutes in cases of angina. A heart attack, on the other hand, has permanent muscle damage and requires more extensive treatment.

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Get to know all about angina:- 

1. What causes Angina?

When the coronary arteries are affected and the heart cannot receive enough blood, angina occurs. The factors that affect the coronary arteries supplying blood to the heart are:-

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• Coronary artery disease is the most common cause of angina. In this condition, a plaque a waxy or fatty substance builds up in the coronary arteries, narrowing or hardening them, thus reducing blood flow to the heart.

• Women usually experience coronary microvascular disease, which damages the walls of tiny blood vessels that branch from coronary arteries. Evaluating these microvascular changes requires specialized techniques that are not readily available.

• A  coronary artery spasm may occur without coronary artery disease. It constricts and reduces blood flow to the heart. Diagnosing a coronary artery spasm requires special equipment.

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2. What does angina feel like?

Most people experience it as a squeezing sensation, tightness, or pressure in the chest. To some, it appears like indigestion, while a few cannot describe the sensation. Pain or discomfort arises in the chest and spreads to the neck, jaw, shoulders, arms, back, or belly.

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Angina equivalents refer to the symptoms caused by a lack of oxygen to the heart, but without a typical chest pain. These include fatigue, nausea or vomiting, shortness of breath, or sweating.

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3. Risk Factors

Many risk factors for angina

• Raise the risk of heart problems, directly causing angina.

• Some limit the oxygen-rich blood that can reach your heart.

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Some risk factors can’t be changed, and others can be managed through lifestyle changes and medications.

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They are

• Anaemia.

• Chronic stress.

• A diet loaded with fat, trans fat, sugar, sodium, or refined carbohydrates.

• Excess alcohol consumption.

• exposure to particles like dust from roads, farms, or construction sites.

• Family history of heart disease.

• Heart failure.

•  Valvular heart disease.

• High blood pressure.

• High cholesterol.

• Cardiomyopathy.

• Inflammation.

• Passive smoking.

• Obesity.

• Lack of physical activity.

• Old age.

• Using tobacco in any form- smoking, vaping, or chewing.

• Drugs.

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4. Types of angina

The classification is based on the cause and how it improves with medicine or rest.

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5. Tests

The following tests are used to confirm the presence of angina.

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• An electrocardiogram (ECG) is a quick, painless test that measures the heart's electrical activity. It reveals a current and previous heart attack.

• The chest X-ray reveals the condition of the heart and lungs, and other causes of chest pain. It also reveals heart enlargement.

• Blood tests for certain cardiac proteins that enter the blood after heart damage. The stress test is done when the heart is working harder.

• An echocardiogram, which uses sound waves, creates dynamic images of the heart and how blood flows through it.

• A nuclear stress test involves injecting a radioactive tracer into the bloodstream, and special scanners show how it moves through the heart arteries. Areas where few tracers are present have poor blood flow.

• Cardiac computed tomography (CT) and magnetic resonance imaging (MRI) create images of the heart and chest. CT scans use X-rays, while MRIs create images of the heart using a magnetic field and radio waves.

• A coronary angiogram uses X-ray imaging to examine the heart's blood vessels from the inside. A flexible catheter tube is inserted into a blood vessel, usually in the groin. The arteries become visible on X-ray when dye flows through the catheter. This X-ray is called an angiogram, and the procedure is known as cardiac catheterization.

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Angina vs heart attack

Unstable angina is a warning sign where blood flow is restricted, causing chest pain but no permanent heart damage. NSTEMI (Non-ST elevation myocardial infarction) is a type of heart attack where there is some damage to the heart muscle, but not as severe as in a STEMI.

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How do they differ?

• They cannot be differentiated immediately based on an ECG; however, cardiac enzyme tests, such as troponin, can aid in the diagnosis.

• If the enzymes are elevated, the heart muscle is damaged, which is indicative of a non-ST-elevation myocardial infarction (NSTEMI).

• If these enzymes are normal but symptoms persist, it is unstable angina.

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How does an angina ECG differ from a heart attack ECG?

Angina and heart attack ECGs differ in the electrical abnormalities they reveal in terms of.

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• Severity

• Nature

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Changes in an angina ECG

1. Transient ST-segment depression: These changes often occur during an angina attack but can resolve when blood flow to the heart is restored. The depression is horizontal, down sloping, or upsloping.

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• Morphology of ST Depression
  
  • ST depression can be upsloping, down-sloping, or horizontal.
  • Horizontal or down-sloping ST depression ≥ 5 mm at the J Point in more than two nearby leads indicates myocardial ischaemia.
  • ST depression more than or equal to 1mm indicates a poor prognosis.
  • ST depression more than or equal to 2mm in more than three leads shows a probability of NSTEMI.
  • Upsloping ST depression is nonspecific for myocardial ischemia.

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• Distribution of ST depression
  
  •  In angina, widespread ST depression is seen in leads I, II, V4-V6, and also in III, aVF, or aVL.

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2. T wave changes: inversion or peaking

• The T wave on an ECG represents muscle recharging after a beat.
• T wave inversion occurs when the T wave flips downwards or the peak T waves are sharply tall. T waves can be signs of ischemia, which means that the heart is not getting enough blood.
• These changes are temporary and may occur during or just after an episode of chest pain.

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3. No permanent Q Waves: A Q wave shows the heart's electrical signal traveling through damaged areas. Because angina does not cause permanent damage, Q Waves are not visible. Absent Q waves indicate the muscle is still alive, and the damage is not permanent.

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The angina ECG changes are transient and revert to normal once the episode subsides. If the ischemia (lack of oxygen supply) is severe or prolonged, the ST segment elevates, indicating a high risk of heart attack.

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Changes in a heart attack ECG

shows more significant and persistent ECG changes,

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• ST-segment elevation: Indicates myocardial infarction (heart attack), complete or near complete coronary artery blockage.

• Q wave formation: Pathologic Q waves indicate permanent heart damage.

• T-wave inversion or peaked T waves are seen in heart attacks, but are less specific than ST-segment elevation.

• Arrhythmias: Various rhythm disturbances may also be visible in the ECG.

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Challenges with interpreting angina ECG

• Normal ecg: The ECG is normal between attacks in stable angina, while it may be subtle or absent in unstable angina.

• Reversible estimate changes: Ischemic changes like T wave inversions, ST-segment depression, or ST-segment elevation may be reversible during an attack.

• Non-specific findings: T wave inversion or ST-segment depression occurs in other conditions as well, which makes it difficult to attribute them specifically to angina.

• Interpreting ECG during various stages: ECG changes evolve, being different at onset, peak, and resolution of an angina attack

• Pre-existing conditions: Bundle branch blocks or previous myocardial infarctions make ECG interpretation more difficult.

• Reliance on technology: Software interpretation is unable to distinguish between subtle and complex changes, which can result in errors.

Preventing angina

1. Adopt a heart-healthy lifestyle, which includes

• Avoid smoking and all kinds of tobacco products.

• Eat a heart-healthy diet, such as a DASH diet or a Mediterranean diet, and reduce your consumption of saturated fats, trans fats, sugar, and sodium.

• Manage stress, practise meditation, yoga, journaling, and mindfulness.

• Control your weight.

• Do a physical workout for at least 150 minutes every week.

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2. Manage risk factors

• Manage high blood pressure, high cholesterol, triglycerides, and diabetes.

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3. Take medications as prescribed regularly.

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Conclusion

Angina refers to chest pain caused by reduced blood flow, which prevents oxygen-rich blood from reaching the heart. The cause is a narrowed coronary artery. Although angina is not severe, it can lead to a heart attack.

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ECG measures electrical activity within the heart. The shape and duration of its waves and segments help detect abnormalities in the ECG, leading to a prompt medical response and treatment of the condition.