Question

Which of the following is false about ECG?

• A. P-wave $ \rightarrow $ Atrial depolarization
• B. QRS complex $ \rightarrow $ Ventricular depolarization
• C. T-wave $ \rightarrow $ Ventricular repolarization
• D. ST depression indicates an infarction

Answer 1

Answer: (D)

An electrocardiogram (ECG) records the electrical signal from the heart to check for different heart conditions. Electrodes are placed on the chest to document the heart's electrical signals, which cause the heart to beat. The signals are shown as waves are recorded on an attached monitor.
There are three primary components in an ECG:

• The P wave is a small upward wave that represents electrical excitation or depolarization of the atria that leads to contraction of both the atria. This is due to the trigger or activation of the SA node.
• The QRS complex represents the depolarization of both ventricles, which initiates the ventricular contraction (ventricular systole). The contraction of the ventricles start shortly after Q and marks the beginning of the systole.
• The T wave represents the repolarization (relaxation) of the ventricles (from excited to normal state). The end of the T-wave marks the end of the systole.

A depression in the ST segment of the ECG generally indicates myocardial ischemia. It is a condition in which the blood flow to the heart is obstructed due to the partial or complete blockage of a coronary artery. The blockage is a result of the accumulation of plaque in the arteries, which is known as atherosclerosis or coronary heart disease. If the plaque buildup in the coronary artery ruptures, it may lead to a heart attack or myocardial infarction.
Enlarged Q and R waves denote a myocardial infarction. A flat T-wave is observed in coronary heart disease.