Understanding Electrocardiogram (ECG) Test

Study Notes

An electrocardiogram (ECG or EKG) is a non-invasive medical test that records the electrical activity of the heart.

Electrodes (small sensors) are placed on the skin, usually on the chest, arms, and legs
These electrodes detect the tiny electrical impulses produced by the heart muscle
The impulses are transmitted to an ECG machine, which records the activity
The machine prints out a graph of the heart's electrical activity, allowing doctors to interpret the results

P wave: represents the electrical activity of the atria (upper chambers of the heart)
QRS complex: represents the electrical activity of the ventricles (lower chambers of the heart)
T wave: represents the ventricles recovering and preparing for the next heartbeat
PR interval: the time between the P wave and the QRS complex, representing the time it takes for the electrical signal to travel from the atria to the ventricles
QT interval: the time between the QRS complex and the T wave, representing the time it takes for the ventricles to recover and prepare for the next heartbeat

Arrhythmias (abnormal heart rhythms): such as atrial fibrillation, ventricular tachycardia, and heart block
Coronary artery disease: damage to the heart muscle due to reduced blood flow
Cardiac chamber enlargement: enlargement of the heart's chambers
Electrolyte imbalance: abnormal levels of electrolytes such as potassium, sodium, and calcium
Heart attack: damage to the heart muscle due to a blockage in the coronary arteries

Resting ECG: a standard ECG performed while the patient is at rest
Stress ECG: an ECG performed while the patient is exercising or under physical stress
Holter monitor: a portable ECG device worn for 24-48 hours to monitor the heart's activity over time
Event monitor: a portable ECG device worn for a longer period of time to monitor the heart's activity during specific symptoms or events

Electrodes (small sensors) are placed on the skin, usually on the chest, arms, and legs
Detects tiny electrical impulses produced by the heart muscle
Transmits impulses to an ECG machine, which records the activity
Machine prints out a graph of the heart's electrical activity

P wave: represents atria's electrical activity (upper chambers of the heart)
QRS complex: represents ventricles' electrical activity (lower chambers of the heart)
T wave: represents ventricles recovering and preparing for the next heartbeat
PR interval: time between P wave and QRS complex (atria to ventricles signal travel time)
QT interval: time between QRS complex and T wave (ventricles' recovery and preparation time)

Arrhythmias (abnormal heart rhythms): atrial fibrillation, ventricular tachycardia, heart block
Coronary artery disease: damage to heart muscle due to reduced blood flow
Cardiac chamber enlargement: enlargement of heart's chambers
Electrolyte imbalance: abnormal levels of potassium, sodium, calcium
Heart attack: damage to heart muscle due to coronary artery blockage

Resting ECG: standard ECG performed while patient is at rest
Stress ECG: ECG performed while patient is exercising or under physical stress
Holter monitor: portable ECG device worn for 24-48 hours to monitor heart's activity over time
Event monitor: portable ECG device worn for a longer period to monitor heart's activity during specific symptoms or events