ECG Interpretation

Question 1

When should an ECG be obtained for chest pain?

Answer 1

Within 10 minutes of chest pain onset.

Question 2

What does the P wave represent?

Answer 2

Atrial depolarization and atrial contraction.

Question 3

What is the difference between the P wave and the PR interval?

Answer 3

The P wave is the small upward bump showing atrial depolarization, while the PR interval is the entire time from the start of the P wave to the start of the QRS complex, representing conduction from the SA node to the AV node.

Question 4

What does the QRS complex represent?

Answer 4

Ventricular depolarization (atrial repolarization occurs at the same time but is hidden) and needs to be less than 0.12 seconds.

Question 5

What does the T wave represent?

Answer 5

Ventricular repolarization – the ventricles are relaxing and refilling with blood.

Question 6

What does the PR interval represent and what is its normal range?

Answer 6

Time between the SA node and AV node conduction; normal range is 0.12–0.20 seconds.

Question 7

What does T wave depression (inversion) indicate?

Answer 7

Myocardial ischemia.

Question 8

What does ST segment elevation indicate?

Answer 8

Myocardial injury.

Question 9

What does Q wave enlargement indicate?

Answer 9

Myocardial infarction.

Question 10

What is a ventricular arrhythmia?

Answer 10

An abnormal rhythm in the ventricles.

Question 11

Why are ventricular arrhythmias dangerous?

Answer 11

Because the ventricles pump blood to the body, and if they don’t work properly, blood flow stops.

Question 12

What happens to oxygen delivery in ventricular arrhythmias?

Answer 12

Oxygen does not reach the brain or body, which can lead to collapse or death quickly.

Question 13

What is an atrial arrhythmia?

Answer 13

An abnormal rhythm in the atria.

Question 14

Why are atrial arrhythmias usually less deadly?

Answer 14

Because the ventricles can still pump blood, so circulation is reduced but not stopped.

Question 15

What happens to blood flow in atrial arrhythmias?

Answer 15

Blood flow is reduced, but the body still receives some oxygen.