ECG basics Practice Questions
20 free ECG basics practice questions for the Physiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which ECG wave represents atrial depolarization?
- A QRS complex
- B P wave
- C T wave
- D U wave
Correct answer: P wave
The P wave reflects depolarization of the atria. It occurs before ventricular depolarization and indicates atrial contraction.
The QRS complex represents:
- A Atrial repolarization
- B Ventricular repolarization
- C Atrial contraction
- D Ventricular depolarization
Correct answer: Ventricular depolarization
The QRS complex corresponds to ventricular depolarization. It is usually large due to the greater muscle mass of the ventricles.
Which ECG wave corresponds to ventricular repolarization?
- A P wave
- B Q wave
- C T wave
- D R wave
Correct answer: T wave
The T wave represents ventricular repolarization. It follows the QRS complex and indicates recovery of the ventricles.
The PR interval represents the time between:
- A Atrial depolarization and ventricular depolarization
- B Ventricular depolarization and full repolarization
- C Atrial repolarization and the onset of ventricular contraction
- D The onset of the QRS complex and the end of the T wave
Correct answer: Atrial depolarization and ventricular depolarization
The PR interval reflects the time taken for electrical impulses to travel from the atria to the ventricles through the AV node.
Which component of ECG reflects ventricular depolarization duration?
- A P wave
- B PR interval
- C QRS duration
- D ST segment
Correct answer: QRS duration
The QRS duration represents the time taken for ventricular depolarization. A prolonged duration may indicate conduction abnormalities.
Which ECG segment is normally isoelectric and represents early ventricular repolarization?
- A PR segment
- B QT interval
- C TP segment
- D ST segment
Correct answer: ST segment
The ST segment is normally flat (isoelectric) and represents the period between ventricular depolarization and repolarization.
The QT interval represents:
- A Atrial depolarization time only
- B Atrial repolarization time only
- C The AV nodal conduction delay alone
- D Total time of ventricular activity
Correct answer: Total time of ventricular activity
The QT interval represents the total duration of ventricular depolarization and repolarization.
Which lead records the electrical activity between the right arm and left arm?
- A Lead I
- B Lead II
- C Lead III
- D aVF
Correct answer: Lead I
Lead I measures the electrical potential difference between the right arm and left arm electrodes.
Which lead is most commonly used for rhythm monitoring?
- A Lead I
- B Lead III
- C aVL
- D Lead II
Correct answer: Lead II
Lead II is commonly used for rhythm monitoring as it aligns well with the heart's electrical axis and clearly shows P waves.
Which ECG wave is usually hidden within the QRS complex?
- A P wave
- B T wave
- C U wave
- D Ta wave
Correct answer: Ta wave
Atrial repolarization (known as the Ta wave) occurs at the same time as ventricular depolarization and is masked by the much larger QRS complex, so it is not normally visible on a standard ECG.
A prolonged PR interval indicates:
- A Faster AV conduction
- B Increased ventricular contraction
- C Reduced atrial activity
- D Delayed AV conduction
Correct answer: Delayed AV conduction
A prolonged PR interval suggests delayed conduction through the AV node, as seen in first-degree heart block.
Which ECG abnormality is associated with hyperkalemia?
- A Peaked T waves
- B Flattened T waves
- C Prolonged PR interval
- D Absent P waves
Correct answer: Peaked T waves
Hyperkalemia causes tall, peaked T waves due to altered repolarization of ventricular cells.
Which ECG feature is most affected in bundle branch block?
- A P wave
- B PR interval
- C QRS duration
- D T wave
Correct answer: QRS duration
Bundle branch block delays ventricular conduction, resulting in a widened QRS complex.
The electrical axis of the heart is normally directed:
- A Downward and to the left
- B Upward and towards the right
- C Horizontally
- D Upward and to the left
Correct answer: Downward and to the left
The normal electrical axis is directed downward and to the left, reflecting the dominant mass of the left ventricle.
Which ECG wave follows immediately after the QRS complex?
- A T wave
- B P wave
- C U wave
- D PR segment
Correct answer: T wave
The T wave follows the QRS complex and represents ventricular repolarization.
Which ECG parameter is used to estimate heart rate?
- A RR interval
- B PR interval
- C QT interval
- D ST segment
Correct answer: RR interval
The RR interval measures the time between consecutive heartbeats and is used to calculate heart rate.
Which condition may cause ST segment elevation?
- A Myocardial infarction
- B Severe hypokalemia
- C Severe chronic anemia
- D Persistent bradycardia
Correct answer: Myocardial infarction
ST segment elevation is commonly seen in acute myocardial infarction due to injury to the cardiac muscle.
Which ECG wave may be seen after the T wave in some individuals?
- A P wave
- B Q wave
- C U wave
- D R wave
Correct answer: U wave
The U wave may follow the T wave and is sometimes associated with repolarization of Purkinje fibers.
Which part of the ECG represents the time taken for impulse conduction through the ventricles?
- A PR interval
- B QRS complex
- C ST segment
- D QT interval
Correct answer: QRS complex
The QRS complex reflects the spread of electrical impulse through the ventricles.
Which ECG interval includes both ventricular depolarization and repolarization?
- A PR interval
- B ST segment
- C QT interval
- D RR interval
Correct answer: QT interval
The QT interval includes both depolarization and repolarization phases of the ventricles, representing total ventricular activity.