Electrocardiogram, Waves, Types, Working and Why it is Done

Electrocardiogram: An electrocardiogram, also known as an EKG or ECG, is a quick and easy diagnostic procedure that evaluates how well the heart is working.  Electrodes, or tiny, sticky patches, are applied to particular parts of the arms, legs, and chest and then lead wires are used to connect them to an ECG machine. The machine records and prints the electrical activity of the heart without sending any electricity into the body.

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Electrocardiogram Types

1. Resting ECG: This is the most commonly used ECG method. It requires placing electrodes on the chest, arms, and legs while the patient lies down. The heart's electrical activity is recorded for a brief period, typically around 10 minutes. A resting ECG aids in detecting abnormal heart rhythms, heart attacks, and other cardiac issues.
2. Stress ECG (exercise stress test): The doctor monitors the patient's heart rate and rhythm while they exercise on a treadmill or stationary bike to see how the heart responds to exertion. A stress ECG helps in identifying blood flow issues to the heart, such as coronary artery disease.
3. Holter Monitor: This portable ECG device is worn for 24 to 48 hours during normal daily activities. It continuously records the heart's electrical activity, which can reveal irregular heartbeats not captured by a resting ECG.
4. Event Recorder: A small, portable ECG device worn for a few weeks or months. Patients press a button when experiencing symptoms like chest pain or palpitations, enabling the device to record the heart's electrical activity at that moment, aiding in identifying the symptom's cause.
5. Signal-averaged ECG (SAECG): A specialized ECG used to diagnose arrhythmogenic right ventricular cardiomyopathy (ARVC), a condition that can lead to sudden death. SAECG is a more intricate test than a standard ECG and is not as widely accessible.

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Electrocardiogram (ECG) Working

How Does an ECG Function?

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Electrocardiogram Waves

• P wave: Indicates the spread of the electrical impulse through the atria (upper chambers), causing them to contract.
• QRS complex: Reflects the impulse's passage through the ventricles (lower chambers), stimulating their contraction.
• T wave: Represents the ventricles' relaxation.
• U wave: Reflects atrial repolarization (may not always be visible on a normal ECG).

What Information Does an EKG Detect?

• Heart rate: The number of heartbeats per minute.
• Heart rhythm : Whether the heart rhythm is regular or irregular.
• Size and positioning of the heart chambers.
• Blood flow to the heart muscle.
• Prior heart muscle damage from a past heart attack.
• Other cardiac issues, such as arrhythmias (irregular heart rhythms) or conduction abnormalities.

• Coronary artery disease
• Heart attack
• Arrhythmias
• Heart valve disorders
• Heart muscle abnormalities

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Why ECG is Done?

1. Determining Conduction Time: Surgeons use the ECG to measure the time it takes for an electromagnetic pulse to traverse the heart. They do this by calculating time intervals on the ECG, and observing whether the electrical activity is natural, sluggish, fast, or erratic. This helps determine how long a pulse takes to travel from one part of the heart to another.
2. Assessing Heart Condition: Cardiologists can assess if areas of the heart are enlarged or overworked by measuring the electrical activity flowing through the heart muscle. A traditional 12-lead ECG involves placing ten electrodes on the patient's arms and chest. The average strength of the heart's electrical potential is then calculated from 12 different angles (known as "leads") over a period, typically 10 seconds. This process allows for the observation of the total intensity and trajectory of the heart's electrical depolarization during the cardiac cycle.

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Electrocardiograms Risks

• Movement or talking during the ECG test
• Smoking or engaging in vigorous exercise prior to the test
• Pregnancy
• Obesity
• Certain medications
• Abdominal swelling caused by fluid accumulation (ascites)
• Electrolyte imbalances, such as abnormal levels of calcium, potassium, or magnesium in the blood