What Can Affect ECG Results

An ECG is a diagnostic tool that records the heart's electrical activity and detects irregular rhythm, heart diseases, or other cardiac conditions. The accuracy of ECG readings is affected by several factors that cause incorrect interpretations. These factors are essential for healthcare providers for reliable results and to make informed clinical decisions.

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Resting ECG is the standard process for assessing heart conditions. Everyone involved in the ECG performing team must be aware of these fundamentals. Ignoring the data could impact resulting interpretations, diagnoses, and patient treatment plans.

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We must not ignore ECG results and what factors can influence their precision. Let us study all the factors affecting ECG, how they work, and what we need to know about how they influence their accuracy.

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Environmental Factors Affecting ECG Accuracy

ECG uses electrical signals to give detailed information on heart health. These signals are affected by several external factors. External conditions such as temperature, humidity, electromagnetic interference, and improper electrode placement affect ECG readings.

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It is a must to understand how these factors influence results. Electromagnetic fields from devices such as mobiles and medical equipment disrupt ECG signals and compromise data integrity.

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• Electromagnetic interference: Strong electromagnetic fields formed by mobile phones and other electronic equipment disrupt the ECG signals forming artifacts.
  

• Motion artifacts: Movements cause noise in the ECG, affecting the clarity and accuracy.
  

• Skin preparation: Moisture, oils, or lotions in the region where the electrodes are placed on the skin affect the quality and lead to inaccurate readings.
  

• Temperature and humidity: High temperatures and high humidity also affect skin conductivity and electrode performance, causing poor contact and distorted signals.
  

• Placement of electrodes: Incorrect electrode placement leads to distorted ECG; proper placement is crucial for obtaining accurate readings.

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Physiological Factors

ECG is a tool for assessing heart health, various physiological factors influence its accuracy. Certain conditions within the body, such as electrolyte imbalances, heart rhythm abnormalities, and hormonal fluctuations, alter the electrical signals captured during the test.

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Stress, physical exertion, and underlying medical conditions affect the results. It is necessary to understand the physiological elements that affect the ECG readings for accurate diagnosis and effective treatment planning.

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1. Heart rate variability (HRV)

• It is variations between consecutive heartbeats.

• The autonomic nervous system controls HRV. ANS regulates involuntary body functions such as heart rate, blood pressure, temperature, and respiratory rate.

• It regulates our body’s fight-or-flight response, which means it speeds up our response.

• Under relaxation, our body slows down.

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With the processing of the information, the brain transmits signals to the rest of the body. The brain transfers signals to the body through the ANS to stimulate or relax its functions.

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When the body is in flight or fight mode, the variation or difference between heartbeats is minimal, and when it is relaxed, the variation is significant. Stress, sleep quality, fitness level, medications, and underlying health conditions influence heart rate variability.

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2. Breathing patterns

Breathing patterns can influence ECG rate and rhythm. Deep or rapid breathing causes changes in heart rate variability. Holding one's breath alters electrical signals, and sleep apnoea or anxiety-related hyperventilation causes irregularities. Breathing affects ECG in the following ways.

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Diaphragm movement

The different movement alters the heart's position since the pericardium is attached to it.

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• During deep inhalation, the diaphragm flattens, lowering the heart's position and shifting it backward and to the right.

• During exhalation, the diaphragm elevates, returning the heart to its original position.

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These positional changes affect the ECG readings.

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Respiratory sinus arrhythmia RSA.

Heart rate increases during breathing in and decreases during breathing out.

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• The Vagus nerve controls through parasympathetic inputs.

• Inspiration reduces vagal stimulation, increasing heart rate.

• Expiration increases vagal input, slowing it down.

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On an ECG, this results in a shortened R-R interval during inspiration and a prolonged R-R interval during expiration.

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3. Muscle artifacts

Muscle activity interferes with ECG recordings. It creates interferences with electrical signals. Shivering, tremors, or shifting create artifacts. It can even happen when patients prop themselves up with their arms. Proper patient position and stationary positions are essential to reduce interference and ensure accurate ECG readings.

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4. Body temperature fluctuations

Body temperature variations also cause changes in the heart rate. Both high and low temperatures affect the ECG.

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5. Electrolyte imbalances

Variations in potassium, sodium or calcium affect ECG. The altered balances lead to changes in heart rhythm, causing arrhythmias or conduction disturbances.

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Sodium

Increased and decreased sodium levels do not have any effect on ECG.

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Calcium

Hypercalcemia or increased calcium causes the following changes in his ECG.

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• Shortened QT interval.

• Lengthened QRS duration.

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Hypocalcemia or decreased calcium causes the following changes in ECG.

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• Lengthened QT interval.

• Shortened QRS duration.

• Bradycardia may occur.

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Potassium

It is important for depolarization and repolarization of the heart. There is a strong correlation between potassium and ECG changes.

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Hyperkalemia

• It decreases impulse transmission in the heart.

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Hypokalemia

• The T waves become wider with lower amplitude T wave inversion also occurs.

• ST-segment depression develops and, along with T-wave inversion, causes ischemia.

6. Hormonal changes

Fluctuations in estrogen and testosterone levels influence heart rate and rhythm in ECG. Hormonal changes during the menstrual cycle in women lead to changes in heart rate and blood pressure.

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Technical Factors

ECG interpretation depends on.

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• Skill of the practitioner.

• Quality of data captured.

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Technical factors play a crucial role in the accuracy of ECG results. The interference, calibration, and functioning of the ECG machine are vital. Outdated or malfunctioning equipment produces errors in results. Attention to all technical details is also required for high-quality ECG waveforms.

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1. Electrode storage and selection

While selecting or using electrodes following features should be kept in mind.

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• The electrodes should be applied as soon as they are pulled out from the storage pouch.

• They should be stored in airtight bags away from light and heat.

• The expiry date on electrodes should be checked before using them.

• Not all electrodes can be used with all ECG devices, so select one that is most adaptable.

• Use one electrode brand at a time; do not use multiple brands or mix them. The resistance may vary from one manufacturer to another.

• Do not adjust the electrode size or shape, as this can impact readings.

2. Electrode placement

Improperly placed electrodes can lead to errors in interpretation, misdiagnosis, and mismanagement of patients.

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• Clear hair from the patient's chest where the electrodes are to be placed to increase contact and reduce patient discomfort while removing electrodes.

• The skin should be cleaned to remove lotion, powders, or oils that interfere with electrical conduction and dried to improve electrode attachment.

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3. Lead reversals or misconnections

Inaccuracies occur when ECG leads are incorrectly connected, or the leads are swapped to the wrong electrodes, creating a wrong interpretation of the heart’s electrical activity.

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4. Interference from other devices

Electromagnetic interference occurs due to smartphones and wearable devices such as smartwatches and activity trackers.ECG systems detect interference caused by GSM mobile phones when placed too close to the electrodes of a patient.

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• To avoid electromagnetic interference, the patient must remove and switch off all electronic devices. All other electronic equipment can also emit electromagnetic signals, which can interfere with ECG signals.

• Movements from nearby construction can also cause signal interference.

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5. Electrical noise (50 to 60 Hertz)

They are commonly seen in ECG recordings because of power lines and electrical equipment. The interference obscures electrical signals from the heart and makes it difficult to interpret ECG accurately. Using appropriate filters to reduce electrical noise improves the quality of the ECG.

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Medications

Many medications cause changes in the ECG. This fact should betaken into consideration while interpreting ECG.

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Cardiovascular drugs

Cardiovascular drugs treat cardiovascular diseases and affect the heart's electrical activities, causing changes in the ECG.

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Antidepressants

Tricyclic antidepressants, TCA, are medications used to treat depression. In cases of overdose, TCA can affect the heart's electrical conductivity and block sodium channels. It causes characteristic changes, which include.

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• Prolonged QRS complexes: The duration of this exceeds 100 milliseconds. QRS duration of over 160 milliseconds raises the risk of ventricular arrhythmias.

• Sinus tachycardia: An elevated heart rate is commonly observed.

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Antipsychotics

These medications affect ECG by prolonging the QT interval and increasing the list of life-threatening arrhythmias, such as torsades de pointes. These drugs disrupt cardiac repolarization because of their impact on the ion channels. Regular monitoring is essential for patients on antipsychotics to detect potential complications.

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Diuretics

Diuretics lead to electrolyte imbalances, causing hypokalaemia. The ECG changes visible are flattened T waves and the presence of U waves. These alterations carry the risk of arrhythmias. Electrolyte levels and ECG readings in patients on diuretics should be evaluated carefully.

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Stimulants

Caffeine and other stimulants elevate heart rate and cause arrhythmias. Caffeine leads to increased catecholamine release, and the amphetamine stimulates the central nervous system, causing tachycardia.

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Medical conditions

They affect ECG results by altering the heart's electrical activity and conduction pathways.

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Respiratory system

The lungs are responsible for oxygenating blood, and the heart pumps the oxygen-rich blood throughout the body. When the lungs are not able to get oxygen from the air, the heart must work hard to deliver oxygen to the body. It increases the workload and can lead to changes in the heart's electrical activity, which can be detected on an ECG.

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Some of the abnormalities associated with pulmonary disease are:

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Neurological conditions

Neurological conditions like Parkinson's disease and seizures influence ECG results by ordering autonomous regulation and heart rate variability. Parkinson's disease leads to bradycardia and other rhythm abnormalities due to autonomic dysfunction.

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Neurological damage can cause changes like ST-segment elevation or depression, T wave inversion, and prolonged QT intervals. These are abnormalities seen in patients with stroke or traumatic brain injury.

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Metabolic Disorders

Diabetes and thyroid conditions are metabolic disorders that impact ECG. Diabetes leads to autonomic neuropathy, causing changes in heart rate variability and arrhythmias. Hypothyroidism causes tachycardia and changes in QT interval.

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Cardiac Conditions

Coronary artery disease and cardiomyopathy cause alterations in ECG. They effect the ST segment indicative of ischemia or infarction. Cardiomyopathy leads to arrhythmia and abnormal waveforms due to impaired muscle function.

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Lifestyle Factors

Lifestyle factors influence the accuracy of ECG. Everyday habits, diet, physical activity, stress, and substance abuse can alter heart rate, rhythm, and overall electrical activity. Inadequate sleep, dehydration, and caffeine or nicotine consumption also lead to changes in ECG. Recognizing these lifestyle choices impacts heart function. It is essential to diagnose.

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1. Caffeine consumption

Caffeine consumption affects ECG results by increasing heart rate and causing arrhythmias. The central nervous stimulant caffeine increases catecholamine release, leading to vibration or changes in heart rhythm. Excessive intake of caffeine leads to severe cardiovascular disturbances, including sinus tachycardia, polymorphic ventricular tachycardia, and ventricular fibrillation.

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2. Smoking

Tobacco is consumed as cigarettes. It contains nicotine, which causes physical and psychological dependence. Cigarette smoking also increases blood coagulability. Nicotine, a primary component of tobacco products, influences ECG in the following ways. 

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• Increases heart rate by stimulating the sympathetic nervous system.

• Shortened RR interval.

• Shortens QT and ST segments.

• Increases the supraventricular and ventricular ectopic beats.

• Causes ischemic ST and T wave changes.

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Other components in tobacco smoke may also play a role in ECG changes.

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3. Alcohol consumption

Moderate alcohol consumption is associated with cardiovascular benefits. However, excessive drinking poses a risk to the heart. Alcohol consumption leads to the following changes in the ECG.

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• Prolonged P wave.

• Prolong QT intervals.

• T wave abnormalities.

• QRS, Complex prolongation.

• ST segment depression.

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These changes are reversible and removed if alcohol is eliminated from the system. Acute alcohol consumption leads to arrhythmias and is referred to as holiday heart syndrome, a condition arising from binge drinking followed by abstinence.

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4. Physical Training

Physical activity influences ECG results. Regular exercise promotes cardiovascular fitness and improves heart efficiency. Athletic training induces several physiological adaptations in the heart. Recognizing these normal variations is essential in distinguishing between benign adaptations and pathological conditions.

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Common ECG changes in athletes are:

• Sinus bradycardia Slow heart rate below 60 beats per minute.

• Increased QRS voltage as left ventricular hypertrophy is a normal variant in athletes.

• Incomplete right bundle branch block. It is a delay in right ventricular conduction, is common in athletes, and is benign.

• Early repolarization featuring ST segment elevation in precordial leads is seen in athletes as a normal variant.

5. Sleep deprivation

Acute and chronic sleep disturbances lead to alterations in ECG readings that negatively impact ECG results. Increasing the sympathetic activity Increases heart rate and arrhythmias. Insufficient sleep also affects cardiac autonomic regulation, resulting in heart rate variability.

6. Stress and anxiety

They affect ECG results by triggering an increased heart rate and altered heart rhythms. When the body responds to stress, it releases catecholamines, which leads to vibrations and changes in ECG.

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They are

• Sinus tachycardia.

• ST segment depression.

• T wave changes.

• Increased QT interval variability.

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Patient-Related Factors in ECG

Several patient-related factors affect ECG accuracy underlying medical conditions also influence these findings.

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1. Age

With increasing age, the heart's electrical system also changes. Older adults show slow conduction, bundle branch blocks, or arrhythmias. Other age-related. Conditions such as hypertension and coronary artery disease also influence ECG.

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2. Sex

Women tend to have longer QT intervals. Hormonal changes during pregnancy and menopause also affect heart rate and rhythm.

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3. Body size and composition

Obesity interferes with the electrode placement, leading to reduced clarity in the signals. The increased muscle mass alters wave amplitudes. Thin individuals have low voltage patterns that may occur, making it important to adjust them.

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4. Medical history

Heart disease, diabetes, and electrolyte imbalances cause abnormal rhythms of wave patterns. Medications being taken by the patient also affect the ECG. 

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5. Genetics

ECG traits such as QT interval, QRS duration and P wave characteristics have a heritable component. 

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Conclusion

Equipment quality, awareness and clinical symptoms are important for obtaining accurate tracings and for minimizing diagnostic errors. Gauze, with its comprehensive approach, considers all factors for the accuracy of ECG interpretation, leading to better patient outcomes and effective management of cardiovascular conditions.