What is an ECG?

An electrocardiogram, or ECG, is a non-invasive, painless, and common diagnostic test. It measures the electrical activity of the heart, helping doctors identify various heart conditions, such as arrhythmia, heart attack, or enlarged heart. The electrical impulses coordinate contractions of different parts of the heart and keep the blood flowing.

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The ECG records these impulses to show the beatings of the heart, the rhythm, and the timing of electrical impulses as they move through different parts of the heart. Changes in an ECG may be a sign of a heart-related condition. Willem Einthoven, a Dutch doctor and professor of Physiology at the University of Leiden, invented the ECG machine.

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With the invention of the ECG machine, the healthcare industry changed forever. Today, ECG is a common term. ECG machines are found in medical offices, hospitals, operating rooms, and ambulances. Even personal devices like smartwatches and telephones can do simple ECGs.

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Clinical applications of ECG

ECGs have numerous clinical applications in diagnosing and managing hard conditions. They helped to diagnose and monitor arrhythmias such as atrial fibrillation and ventricular tachycardia. They also help to identify signs of cardiac chamber enlargement and conduction disorders. They are used to diagnose and monitor acute coronary syndromes such as myocardial infarction and cardiac ischemia.

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They are used to evaluate certain medications' cardiac effects and monitor patients with no heart conditions, such as heart failure and cardiomyopathy. They play a role in preoperative evaluation by identifying patients at high risk of cardiac complications.  They allow targeted interventions and informed decision-making.

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 Why do an ECG?

An electrocardiogram checks the heartbeat. It shows how fast or slow the heart may be beating. It helps to diagnose.

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• Irregular heartbeats, arrhythmias.

• A previous heart attack.

• Cause of chest pain

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An ECG assesses the working of pacemakers and heart disease treatments

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Other needs for an ECG may be

• Chest pain

• Dizziness, light, and headedness or confusion.

• Pounding, skipping, or fluttering of the heart.

• Fast pulse. Shortness of breath.

• Fatigue.

• Reduced ability to do exercise.

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ECG is mandatory if you have a family history of heart disease and for screening heart diseases. ECG screening is advisable for even those with a low risk of heart disease and those who have no symptoms. Most physicians consider ECG as a basic tool to screen for heart disease, although it needs to be individualized.

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Risks in ECG

Risks associated with ECG or minimal and rare. One may feel some discomfort when sticky electrodes are taken off. If left for a very long time, they may irritate. Conditions which affect the results of ECG are

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• Obesity

• Movement during the test.

• Exercise or smoking before the test.

• Medications

• Electrolyte imbalances- Too much or too little potassium, calcium, And magnesium in the blood.

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Types of ECG

A standard 12 lead ECG provides a comprehensive view of the heart’s electrical activity from various angles. It records electrical signals from 12 different leads placed on the body surface, representing a detailed heart function.

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Various types of ECGs are

• Resting ECG: It measures the heart’s electric activity while the patient is at rest to identify abnormalities.

• Stress ECG: It monitors heart activity during physical exertion and assesses heart performance under stress.

• Holter Monitor: A Holter monitor records heart activity over 24 to 48 hours and detects irregularities not captured in a standard ECG.

• Event Recorders: They capture the ECG data during symptoms or episodes. They are worn for weeks to identify intermittent disturbances. One can push the button ON  as one experiences symptoms, switching it OFF as the symptoms subside. 

• Implantable loop recorder: It records continuously and monitors heart activity over long periods to detect infrequent arrhythmias.

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ECG Procedure

ECG procedure begins with the patient lying still on the examination table and electrodes. They are placed on the chest, arms, and legs. These electrodes are connected to an ECG machine to record the heart's electrical activity. The patient is instructed to remain relaxed to avoid any artifacts.

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The procedure lasts about 3 to 5 minutes. The machine captures and displays heartbeats as waveforms on the tracing sheet. After recording, the electrodes are removed, and the healthcare provider analyzes the tracing.

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Preparation for an ECG: 

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The patient should

• Wear comfortable clothes and clean the chest area for electrode placement.

• Remove all metal objects such as bangles, watches, and bracelets as they interfere with the ECG recordings.

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ECG recording: The heart’s electrical activity is recorded through the electrodes and generated as a waveform on the graph representing each beat.

Before and during ECG: As the ECG is taken the patient is instructed to lie down, remain calm, and relaxed during the procedure.

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Regardless of the patient sex, the position of the electrodes is the same. The V1 and V2 flank the sternal borders at the 4th intercostal space. V4, V5. V6. align starting at the 5th intercostal space and V3 goes midway between V2 and V4. Errors occur when placing chest electrodes on a female patient owing to the location and amount of breast tissue. Misplacements and best practices during women’s ECG can lead to incorrect readings or waveforms, causing false positive or false negative diagnoses. The anatomical differences, for example, the breast tissue make it more significant in women.

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Positioning errors disrupt management efforts for patients with cardiac diseases. Society for Cardiological Science and Technology recommends that when breast tissue covers placement areas, ECG professionals place electrodes V4, V5, and V6 under the breast. The risk of misplacement applies to all leads, though position inaccuracies in V4, V5, and V6 are more common than those in V1, V2, and V3, particularly in women who are older and larger. Once the tracing is completed, the leads are disconnected, and the electrodes are removed.

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After an ECG: No special care is needed after an ECG, and one can proceed to the normal diet and activities unless told otherwise. Complaints of chest pain, shortness of breath, dizziness, fainting, and other symptoms should be reported to the healthcare provider before the ECG.

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ECG waves and Intervals

An ECG electrocardiogram records the electrical activity and displays it as a series of waves at definite intervals. The P wave represents the electrical signals that initiate the heartbeat. The QRS complex Indicates the contraction of ventricles. The T wave represents ventricular recovery.

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ECG waves

The waves are the spikes and dips in the line tracings. There of the following types

• P-wave represents the electrical activity of the upper chamber of the heart.

• QRS complex. Represents the electrical activity of the lower heart chamber-ventricles. It is made up of Q, R, and S waves.

• T-wave shows the electrical recovery of ventricles after contraction.

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ECG intervals

The intervals are the time taken for an electrical signal to travel through the heart. These are measured in milliseconds and help to diagnose various heart conditions. They include PR interval, QRS interval, and QT interval.

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• PR Interval. It is the time between P waves and the QRS complex’s start. It indicates the time for an electrical impulse to travel from the atria to the ventricles.

• QRS interval. It measures the width of the QRS complex. Representing the time taken for the ventricles to contract.

• QT interval. It is the time from the beginning of the QRS complex to the end of the T wave. It represents the total time. For the heart to contract and recover.

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Advances in ECG Technology

Artificial intelligence and machine learning algorithms have improved assessing, analyzing, and detection of abnormalities in function. When incorporated in smartwatches and fitness trackers it helps individuals to track and detect abnormalities quickly. They help in the early diagnosis, reduce false positives and negatives, and lead to better patient outcomes.

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Digital ECG

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Advantages

• Provides diagnostic accuracy

• Ease of use

• Remote monitoring capabilities. 

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Disadvantages

• Higher initial cost 

• Potential for errors

• Dependence on internet connectivity

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The salient features are.

• Improved accuracy and clarity: They have improved image quality and noise reduction compared to analog ECGs.

• Computer Analysis: The algorithms help in detecting ECG abnormalities.

• Portability: These can be carried out and used in ambulances and clinics.

Advances in ECG technology

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Wearable ECG devices

Smartwatches and fitness trackers allow continuous heart rhythm monitoring. They detect irregular heartbeats and provide real-time feedback. The accuracy may vary and they are not a replacement for a traditional ACG or medical diagnosis. The salient features are.

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• Variable ECG devices provide continuous monitoring of the heart activity.

• They help in the detection of arrhythmia.

• They provide early warning signs of heart problems.

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Telemedicine and remote monitoring

Telemedicine and remote monitoring enable patients to have quality medical care and consultations from the comfort of their homes. It improves access to healthcare services and reduces hospital admission. However, there are concerns about data privacy, security, potential misdiagnosis, or delayed diagnosis. The salient features are

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• Remote transmission: ECG data can be transmitted remotely to healthcare providers.

• Improved access to care: Especially in remote areas.

• Early detection of heart events

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Limitations of ECG testing

Even though ECG is widely used as a testing tool, it has limitations. They are as follows.

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• It provides a snapshot of the heart's activity, which means that if there are any irregularities between the tests. They are not detected.

• It only detects abnormalities within the heart itself, issues with blood flow In and out of the heart, or blockages in the arteries that cannot be identified through ECG alone.

• Obesity, lung disease, and age-related changes to the heart make interpretation of ECG difficult. To rule out, we need a stress test.

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ECG test has its limitations yet, it remains a valuable tool in diagnosing and monitoring heart conditions.  

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Conclusion

ECG is a preferred diagnostic tool to measure heart electric activity. By placing electrodes on the skin, ECG records electrical impulses that trigger heartbeat and create a wave. This non-invasive test diagnoses various cardiac conditions and recognizes irregular heartbeats and heart attacks. We at Gauze are equipped to support you in interpreting ECG, treating, and managing your patients to improve outcomes.