Can an ECG Detect a Blocked Artery

Arteries of the heart block when a fatty material known as plaque builds up in them, leading to the blockage. When plaque accumulates in arteries, it lowers the amount of blood that can flow. When the blood flowing to the heart is blocked completely, a heart attack occurs.

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A partial heart blockage may not cause symptoms, but as a blockage gets more severe, it can cause shortness of breath, chest pain and dizziness. These symptoms require medical attention. Anytime the blood flow to the heart is reduced, it is a medical emergency that requires investigation.

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An ECG helps to detect abnormalities in the heart. But does it detect blockage in the heart remains a question. In this blog, we will read about the capabilities and limitations of ECGs in detecting blockages.

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Arteries of the Heart

Coronary arteries supply blood to the heart. Like all tissues, heart muscles also require oxygen to work. Coronary arteries surround the heart and supply oxygen-rich blood to its muscles. The two main coronary arteries are:

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1. The left main coronary artery supplies blood to the left ventricle and atrium. It branches into.

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• The left anterior descending artery is a small branch of the left coronary artery supplying blood to the front and the middle (septum) of the left ventricle.

•  The left circumflex artery is another artery that encircles the heart, supplying blood to the outer surface and back of the heart.

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2. The right coronary artery carries blood to the right side of the heart- the right ventricle, atrium, sinoatrial, and atrioventricular nodes. These nodes control the heart rhythm. It further divides into smaller branches.

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•  Right posterior descending artery.

•  The acute marginal artery supplies blood to the middle septum of the heart.

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What is a Heart Blockage?

A heart blockage occurs when plaque accumulates in the arteries that supply blood to the heart. Plaque is composed of fat, cholesterol, cellular waste products, calcium, and fibrin, a clotting substance. When plaque builds up in the blood vessels, it narrows the arteries, causing atherosclerosis.

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Atherosclerosis makes it difficult for blood to flow through the arteries in the body. The narrowing and hardening of the arteries of the heart is known as coronary artery disease. If too much plaque accumulates in these arteries, it causes a complete blockage, leading to a heart attack.

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A heart blockage can be caused by a stray piece of plaque that breaks away from the artery wall, causing a blood clot in the coronary artery, which triggers a heart attack, and the muscles begin to die if the supply is not restored soon.

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How does the plaque form?

Plaque has cholesterol, fat, calcium, fibrin, and cellular waste. Cholesterol, a fat, is needed by every cell in the body, and it also helps in the production of vitamin D and hormones. There are two main types of cholesterol present in our bodies. 

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• High-density lipoprotein (HDL).

• Low-density lipoprotein (LDL).

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LDL, the bad cholesterol, is responsible for plaque buildup in arteries. When plaque builds up in the arteries, white blood cells in the blood are drawn to the site to digest LDL. It produces toxins, attracting more white blood cells to the area, causing inflammation in the arterial wall. When this plaque breaks off, a clot forms, reducing blood flow to organs and body parts.

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Coronary calcification

Calcium in the blood settles on parts of the arterial walls. Damaged, inflamed, or repaired arteries attract more calcium deposits. This process starts at an early age, and calcium deposits start small, about 0.5 microns, and grow gradually. Both calcification and plaque formation continue simultaneously. 

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Symptoms of artery blockage

People with partial blockage may not show symptoms or may notice them when they exert themselves during physical activity or stress, or anxiety.

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Symptoms are

• Feeling tired.

• Chess discomfort.

• Difficulty in breathing.

• Lightheadedness or dizziness.

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There are four grades of symptoms depending on the severity. Grade 4 being the most severe.

• Grade 1: Chest pain during an increase in physical activity or emotional distress.

• Grade 2: Chest pain during activities like fast walking, uphill walking, climbing stairs, after meals, or during emotional distress.

• Grade 3: Chest pain during light walking.

• Grade 4: Chest pain at rest or no physical activity.

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Diagnosis of a heart blockage

Tests, which help you in diagnosing heart blockage, are:

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1. ECG checks the electrical activity of the heart.

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2. Imaging tests echo cardiography and magnetic resonance angiography, provide a view of blood flowing in and around the heart.

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It can be done by

• Cardiac catheterization: Involves a thin tube inserted into the artery, which allows a doctor to view the inside of your heart where plaque has built up.

• Coronary calcium scan: Determines calcification in the arteries.

• Blood test: To check cholesterol, triglycerides, lipoproteins, and proteins that indicate inflammation.

• Stress test: It assesses heart function and determines irregularities in the walls of the heart.

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Lifestyle changes for preventing blocked arteries

Lifestyle changes that prevent the blocking of arteries are:

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• Healthy eating.

• Regular exercise.

• Quitting smoking.

• Managing stress.

• Regular checkups.

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Types of heart blockages

1. Partial blockage (stable angina) occurs when a coronary artery is partially blocked, and pain occurs during exertion but is relieved by rest.

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2. Complete blockage (myocardial infarction) causes heart muscles to die because of no blood supply.

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3. Unstable blockage (unstable angina) has a blockage that suddenly worsens with chest pain at rest.

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4. Silent blockage, some blockages are not visible and can only be detected through tests or accidentally, when evaluating other conditions.

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Can an ECG Detect Coronary Artery Disease (CAD)?

Electrical impulses make the chambers in the heart contract rhythmically to keep the blood flowing. These are recorded on the tracing sheet as spikes and valleys as P, QRS, and T waves and intervals.

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They tell us about

• Signs of damage to the heart.

• Abnormal heart rhythm or arrhythmias.

• Effect of electrolytes and drugs.

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ECG Changes that may Indicate CAD or a Heart Attack

• ST-segment depression.

• ST-segment elevation.

• Flatten T waves.

• Presence of Q Waves.

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ECG to identify the stages of heart disease, CAD

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Stable coronary artery disease

• Shows no changes in heart rhythm.

• During exercise in the stress test, the ECG may show ST-segment changes.

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Acute coronary syndrome (ACS)

• A serious condition where blood flow to the heart is partially or completely blocked.

• ECG may show ST-segment elevation or depression, and Q Waves indicate a previous heart attack.

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Limitations of ECG in detecting blockage

ECG is an invaluable test in diagnosing heart disease, but it has limitations in detecting blockages in coronary arteries, which are:

• Indirect indicators: ECG shows signs that suggest only a possibility of blockage, ST-segment changes indicate myocardial ischemia, but these are not specific to coronary artery diseases and occur in other conditions also.

• Limited sensitivity: If the blockage is insignificant and does not cause ischemia, or if the location where the electrode is placed does not monitor the blockage, the ECG misses it.

• Chronic vs acute blockage: ECG detects acute blockages during a heart attack when the changes are clear, but not when the blockage is chronic and does not cause detectable changes.

• Other existing cardiac conditions complicate interpretation.

• Need more tests like echocardiogram, CT scans, stress test, angiograms.

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Importance of Regular Cardiac Care Monitoring

Factors contributing to heart disease risk are age, family history, lifestyle choices like diet and exercise, and medical conditions like hypertension or diabetes.

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• Regular checkups with healthcare providers provide a timely assessment of heart health.

• Early detection prevents complications.

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Monitoring your Heart at Home

You may be recommended to keep an eye on your heart health at home if you have just discovered you have coronary artery disease. Cell diagnosis of a heart blockage or other heart-related diseases is not possible, but monitoring heart health is:

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• Monitor your blood pressure: A healthy blood pressure ranges between 120 / 80 mmHg. It depends on your age, gender, weight, and the medications you are taking.

• Monitor your heart rate: Measure your pulse count, how many beats you feel in one minute. A healthy, resting heart rate is between 60 - 100 beats per minute.

• Taking the staircase test: An indicator to determine if the heart is working well is to see how quickly and easily you can walk up the flight of stairs. Being able to climb 60 stairs in 90 seconds or less indicates a healthy heart.

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Conclusion

ECG is a useful tool used for early detection of heart diseases like arrhythmias or signs of ischemia, but does not detect blocked arteries standalone. Angiograms, stress tests and other tests are necessary are complementary tests needed for a comprehensive diagnosis.

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It is essential to care for your heart health and consult a healthcare provider for a thorough evaluation. Gauze provides you with a personalised treatment plan.