What Information Does ECG Give about a Person

An electrocardiogram or ECG is a simple, quick and non-invasive test that records the heart's electrical activity. It provides vital information about heart rate and overall function. It is an important tool for diagnosing many cardiovascular conditions. If you are experiencing chest pain, palpitations, or shortness of breath, an ECG is often the first test your doctor may recommend.

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The ECG Tracing shows

• Timing and strength of the heart's electrical signal

• The heart rate and rhythm

• Signs of arrhythmia

• Previous heart attack

• Congenital disabilities that you may be having

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By analyzing these waveforms, healthcare providers can gain a lot of information about a person.

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How Does an ECG Reveal Information about a Person?

An electrical impulse initiates the heartbeat. These impulses are created by the sinoatrial node (SA), called the heart's natural pacemaker. The SA node sends electrical signals that travel through the heart, causing the atria to contract and pump blood into the ventricles of the lower chambers. The signal then moves to the atrioventricular AV node; it is delayed before being transmitted to the ventricles, which then contract to pump blood to the lungs and the rest of the body.

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An ECG measures electrical impulses by placing electrodes on the skin and detects heart activity. These electrodes are connected to the ECG machine, which records electrical activity and displays it on a monitor or paper as a waveform.

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When is an ECG test advised?

An ECG may be required if one is experiencing any of the following symptoms that might indicate a heart issue.

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• Chest pain

• Breathlessness

• Fatigue or weakness

• A feeling of pounding, racing, or fluttering heart

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Risks and benefits of an ECG

An ECG is one of the go-to tests if someone has a heart condition.

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Benefits

• Non-invasive and painless test

• Quick and efficient procedure

• Early detection of heart conditions

• Widely available in healthcare settings

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Risks

False results due to movement or poor electrode placements.

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Types of ECG done

1. Resting ECG: It involves lying on the back calmly and comfortably during the test because tensing your muscles, moving, coughing, or shaking can affect the results.

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2. Exercise ECG: The heart's electrical activity is measured while you are physically active. It involves riding an exercise bike. The exertion is increased, making it more difficult to perform work. Your blood pressure is checked regularly. The test is stopped if any irregularities occur in the ECG. The heart's electrical activity is recorded for 24 hours. Three to four electrodes are attached to your chest, and a small recording device is worn on a belt or hung around your neck.

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It records heartbeats during day-to-day activities. A Holter monitor detects irregular heartbeats that are not evident in a normal ECG. Special devices called event recorders monitor heartbeat irregularities for several years. These recorders are so small they can even be implanted under the skin.

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Insights we Gain from ECG 

An ECG measures the electrical activity of a person's heart, its rate and rhythm, detects abnormalities such as arrhythmias, and shows how electrical signals travel through the conduction system of the heart. The ECG identifies structural changes, such as an enlarged heart, and detects signs of a heart attack.

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ECG helps us detect issues like

• Reduced blood flow to the heart (ischemia)

• Electrolyte imbalances

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That affect heart function, which is necessary to diagnose, monitor, and manage even complex cardiac conditions.

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Heart Rate and Rhythm

Heart rate is how fast or slow the heart is beating, while rhythm is how regular or irregular heartbeats are. Arrhythmias are rhythms of the heart which may be regular or irregular.

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• Bradycardia occurs when the heart beats slowly.

• Tachycardia occurs when the heart beats fast.

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They help to diagnose various underlying heart conditions that require further diagnosis and treatment.

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Electrical conduction pathway

ECG tracks the path that electrical impulses take when traveling from the atria to the ventricles through the AV node and bundle branches. Disruptions in the conduction pathways, such as heart or bundle branch block, lead to irregular heartbeats and are key to diagnosing heart conduction disorders.

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Heart size

An ECG indicates enlarged heart size (hypertrophy) and detects when the heart muscles are damaged due to conditions like high blood pressure or valve disease. Enlarged chambers, especially the ventricles, affect heart function and signal underlying cardiovascular problems. Identifying hypertrophy helps to diagnose heart strain and prevent further complications.

Myocardial ischemia

ECG shows myocardial ischemia when the heart muscles receive insufficient oxygen and reduced blood flow. Indicated by ST segment changes. It identifies myocardial infarction and shows patterns like ST elevation, T wave inversion, or pathologic Q waves. It helps to assess heart damage and guide immediate treatment to prevent further complications.

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Electrolyte imbalances

Electrolyte imbalances, such as abnormal potassium or calcium levels, affect heart function and are detectable on the ECG. Changes in T waves, QT intervals, or other waveform abnormalities indicate hyperkalaemia or hypokalaemia. It is essential to identify these imbalances as they have dangerous consequences.

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‍Risk of cardiovascular diseases

An ECG not only assesses the risk of cardiovascular disease by detecting abnormalities like arrhythmias, heart enlargement, or signs of ischemia. It indicates conditions such as hypertension, coronary artery disease, or heart failure. Early detection of these risks allows preventive measures, lifestyle changes, and treatments to reduce the likelihood of serious heart events.

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What Information Does ECG Give us about a Person?

An ECG can reveal a wealth of information about the person. They reveal information we stumble upon sometimes accidentally.

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Structural abnormalities

They are physical changes in size, shape, or functioning of heart chambers, walls, or valves. These changes result from conditions such as high blood pressure, heart valve disorders, or congenital heart defects. An enlarged heart chamber (dilation) or thickened heart wall (hypertrophy) affects how efficiently the heart pumps blood.

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Specific patterns on ECG, such as altered waveforms, voltage changes, or abnormal conduction, indicate problems like ventricular hypertrophy, atrial enlargement, or valve-related conditions.

1. Chamber sizes and wall thickness

Enlarged chambers or thick walls (hypertrophy) affect heart functions. These changes are visible in conditions like high blood pressure or valve disorders and can be detected through ECG imaging.

• Left ventricular hypertrophy (LVH): Left ventricular hypertrophy is the thickening of the left ventricle due to high blood pressure or heart valve disease. It impairs heart function, increasing the risk of arrhythmias, heart failure, and other complications.

• Right ventricular hypertrophy (RVH): Is the thickening of the right ventricle caused by lung conditions like pulmonary hypertension or congenital heart defects. It leads to decreased heart efficiency, arrhythmias, and right-sided heart failure.

• Left/right Atrial enlargement: High blood pressure, valve disorders, or lung disease cause atrial enlargement. It refers to the thickening or dilation of the atria. It increases the risk of arrhythmia, heart failure, and blood clotting.

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2. Valve Disorders

It includes stenosis, narrowing of the valves, regurgitation, and leakage of blood flow backward. It increases pressure or volume overload in the heart chambers, causing structural changes. ECG and imaging are used to diagnose these conditions.

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• Mitral valve regurgitation occurs when the mitral valve does not close properly, causing blood to flow backward into the left atrium. It causes heart enlargement, arrhythmias, and heart failure if left untreated.

• Aortic stenosis is the narrowing of the aortic valve, which restricts blood flow from the heart to the body. It causes chest pain, fainting, and heart failure and requires valve repair or replacement.

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Cardiac function and performance

The primary function of the heart is to pump blood to various parts of the body. It supplies oxygen and nutrients to all the cells and removes carbon dioxide and waste products.

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Key components to determine heart performance are 

• Heart rate

• Stroke volume

• Cardiac output

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The cardiac function is evaluated by assessing the left and right ventricular performance. Ejection fraction, which indicates heart health. These factors help to diagnose and manage cardiovascular diseases.

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Left ventricle function

The left ventricle pumps oxygenated blood to the body and is essential for diagnosing cardiac functions.

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• Ejection fraction assessment: It measures the percentage of blood ejected from the left ventricle during each heartbeat and is indicative of cardiac efficiency.

• Left ventricular hypertrophy: It is the thickening of the left ventricle due to increased workload from hypertension or aortic stenosis.

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Right ventricular function

It refers to the ability of the right ventricle to effectively pump deoxygenated blood into the pulmonary arteries for oxygenation in the lungs. It is essential to maintain proper pulmonary circulation and overall cardiovascular health.

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• Right ventricular dysfunction: It occurs when the ventricles fail to pump blood efficiently due to pulmonary hypertension or myocardial infarction. It leads to inadequate blood flow to the lungs, causing respiratory issues.

• Pulmonary embolism diagnosis: It involves identifying blood clots in the pulmonary arteries, and standard methods are CT pulmonary angiography, ventilation-perfusion scans, and D-dimer scans.

Cardiac stress or damage

The right ventricle can pump deoxygenated blood into the pulmonary arteries for oxygenation in the lungs. It is essential to maintain proper pulmonary circulation for heart health.

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• ‍Right ventricular dysfunction: It occurs when the ventricles fail to pump blood due to pulmonary hypertension or myocardial infarction. It leads to inadequate blood flow to the lungs, causing respiratory issues.

• Pulmonary embolism diagnosis: It involves identifying blood clots in the pulmonary arteries. Standard methods to diagnose them are CT pulmonary angiography, ventilation-perfusion scans, and D-dimer scans.

Cardiac stress or damage

Heart conditions caused by cardiac stress often show as changes on an ECG.

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ST segment changes

ST-segment changes indicate cardiac ischemia on an electrocardiogram.

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• The ST-segment elevation shows acute myocardial infarction.

• ST-segment depression indicates myocardial ischemia.

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Evaluating these changes helps healthcare providers assess the severity of cardiac events.

T wave abnormalities

T-wave abnormalities are inversion and flattening that indicate cardiac stress or ischemia.

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• Inverted T wave suggests prior myocardial infarction

• Flattened T wave indicates electrolyte imbalance and other systemic issues.

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Monitoring these changes on an ECG helps to assess heart health and make decisions.

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Electrolyte and medication effects

Electrolyte imbalances and medications play an essential role in cardiac function and rhythm. 

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Electrolytes

 Potassium, magnesium, calcium, and phosphorus are essential electrolytes that help the heart to contract.

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• Potassium and magnesium: Hyperkalemia (excess potassium) or hypokalemia (low potassium) causes arrhythmias. Magnesium deficiency also increases them.

• Calcium and phosphorus disorders: Hypercalcaemia and hypocalcaemia affect contraction and conduction and cause arrhythmias. Variations in Phosphorus influence calcium metabolism increasing the heart disease risk.

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Medications

Beta-blockers and antiarrhythmic drugs alter electrical conduction. 

• Beta-blockers reduce oxygen demand and control heart rate.

• Antiarrhythmic drugs target antiarrhythmic pathways. However, certain medications increase QT interval, increasing the risk of Torsades de pointes.

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Congenital and genetic conditions

Congenital and genetic conditions are conditions present at birth resulting from inherited genetic mutations or issues during fetal development. Congenital and genetic disorders impact individuals' overall health and quality of life.

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Some are treatable with medication or surgery, while others require long-term care and lifestyle adjustments. Genetic counseling provides insight into risk and helps families make healthcare decisions.

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Inherited disorders

They are passed down from parents to offspring through genes. These occur because of mutations occurring in the DNA and can be dominant, recessive or linked to a specific chromosome.

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• Long QT syndrome: Is a complex condition affecting electrical activity,y causing prolonged heartbeats. Leading to fainting, seizures, or sudden death. It is often inherited and requires monitoring and treatment.

• Brugada syndrome: It is a genetic disorder that affects heart rhythm, leading to abnormal ECG readings and an increased risk of sudden cardiac arrest. It is often asymptomatic, but it can be life-threatening without treatment.

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Congenital heart defects

The structural abnormalities of the heart develop before birth and affect its function and blood flow.

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• Atrial septal defect: These are holes in the wall between the heart's upper chamber, the atria, which allows oxygenated and deoxygenated blood to mix. It leads to heart and prominent rhythm and pulmonary hypertension over time.

• Ventricular septal defect: These are holes between the heart's lower chambers, causing excess blood to flow to the lungs. It results in heart failure, breathing difficulties, or delayed growth if not treated.

ECG Revelations in Special Populations

The ECG in children, pregnant women, and the elderly, because of their unique physiological and pathological characteristics, requires careful evaluation.

Children 

The heart's electrical activity varies with age and requires adjustment for ECG interpretation.

• Normal variants and abnormalities: Sinus arrhythmia or early repolarization are normal in children’s ECG. They are harmless. Recognizing these nuances is essential to avoid misdiagnosis and unnecessary interventions in patients.

• Congenital heart disease diagnosis: A combination of clinical assessment, imaging, and ECG findings helps detect these anomalies.

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ECG of a healthy 2-year-old boy with many typical features of the paediatric ECG

• Heart rate 110 bpm

• Juvenile T-wave pattern (T wave inversion in V1-3)

• Dominant R waves in V1-3

• RSR pattern (partial RBBB morphology) in V1

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Pregnant women 

Pregnant women have hormones circulating in the body that influence the rate and rhythm of the heart. It is thus essential to differentiate between pregnancy-related adaptations and potential cardiac problems.

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Elderly patients

Comorbidities and age-related changes complicate ECG interpretation. Hypertension and heart failure can have different presentations. A clinician must be vigilant in accessing these nuances on the ECG.

• Age-related changes in ECG are prolonged QT intervals, decreased heart rate variability, and changed conduction times. They complicate interpretations and mask underlying cardiac conditions in older people.

• Diagnostic challenges in older adults arise from the atypical presentation of heart conditions and the presence of comorbidities. They mask symptoms, making it difficult to differentiate between regular aging changes and pathological findings on ECG.

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Conclusion

ECG is a source of valuable information about a person’s cardiac health by assessing heart rhythm, rate, and electrical activity. It helps in diagnosing various heart conditions caused by other factors.

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Our ECG reveals a concentration of electrolytes, congenital disabilities, and aspects we usually overlook, such as the quantity of water we drink. Gauze and their AI support help assimilate these observations to derive logical conclusions and improve patient outcomes.