Dr Gourish Karande explains how an ECG proves to be an invaluable tool for checking heart health.
The heart is an important muscle organ which pumps blood to different parts of the body through veins and arteries. Proper functioning of the heart is necessary for a proper functioning of the body. Irregular functioning of the heart can result in heart disease which also affects the functioning of liver, kidney, brain and the pancreas. Heart tests diagnose the functioning and rhythm of the heart.
Importance of ECG
An electrocardiogram (ECG) is a non-invasive test that detects the functioning of the heart by measuring the electrical activity generated by the heart during contraction. It helps detect blockages in the heart. ECG identifies irregularities in heart rhythm, i.e. the speed of heart rate. It reveals injury or physical changes in the heart muscle. ECG test is used as an assessment and diagnostic tool in pre-hospital, hospital and other clinical settings. It can also be used for continuous monitoring of the functioning of the heart in cases of surgery and implantation.
The ECG is a relatively simple test to perform. It is non-invasive and does not hurt. An electrode lead or a patch is placed on each arm and leg and six are placed across the chest wall. The signals received from each electrode are recorded. The printed view of these recordings is called an electrocardiograph. ECG is the most common test recommended to check the heart rhythm of a person. It measures the heart’s electrical activity and records the duration and voltage of the electrical signals when they pass through the heart. An electrocardiogram (ECG) reports any abnormalities in the heart’s shape and size of the heart chambers mainly in people who have hypertension and heart disease. It detects alteration in serum levels of potassium, calcium and magnesium electrolytes. This helps to detect as well as manage the electrolyte imbalances in the blood. ECG can help identify the presence of ischemia (inadequate blood supply), injury or infarction (tissue death) of the heart muscle.
Elevated readings in an ECG report is the earliest reliable sign that heart attack (myocardial infarction) has occurred and tells if the event is acute. ECG also helps to diagnose arrhythmia (change in normal sinus rhythm). It helps post-operative evaluation in angioplasty, pacemaker implantation and cardiac bypasses surgery.
It is also used for Holter monitoring (24 hours blood pressure monitoring). A person is recommended ECG test if there is:
- Chest pain or discomfort or heaviness
- Difficult breathing
- Heart palpitations
- Fainting or collapse
- Other conditions like jaw pain, shoulder pain, back pain and upper abdominal pain
Performing the test
The person will be asked to change into a gown. The technician will attach 12 soft electrodes (6 on the limbs and 6 on the chest) using a gel. These electrodes are attached to electrical wires which are then attached to the ECG machine. The entire procedure takes about 10 minutes.
Interpreting the results
ECG is a graphic representation of the paper. A normal ECG has P, Q, R, S and T waves in the report. A normal sinus rhythm ECG has an upright P and T wave, normal Q, R and S waves with normal heart rate and rhythm. The three key ECG indicators to identify a heart attack are changes in the T wave, changes in the ST segment (elevation or depression) and appearance of new Q wave. The electrical signals of the heart (or the voltage) are measured along the vertical axis and are expressed in millimetre (mm). The duration or time is measured along the horizontal axis in squares. There are large squares which are divided into smaller squares. A healthy adult has a heart rate of 60 to 100 beats per minute (bpm). A heart rate of above 100 or below 60 is considered abnormal. A heart rate below 60 is called bradycardia (slow heart rate) and above 100 is tachycardia (heart rate which is faster than the normal range).
ECG is an inexpensive and non-invasive test. It is easily accessible, simple to interpret and provides detailed information about the heart health of a person. It is quick, painless and harmless. It can be easily done in any primary healthcare centre or at any testing centre.
The test is very safe and risk-free. So far, there are no disadvantages or contraindication seen of ECG in any individual.
Dr Gourish Karande is an Intensivist and consultant Physician.