Q: If the R-R interval on an ECG is 20 mm, what is the duration of one cardiac cycle? (Each 1 mm = 0.04 s)

$$20 \times 0.04 = 0.80\ \text{s}$$

Q: If the R-R interval is 15 mm on an ECG, what is the heart rate? (1 mm = 0.04 s)

$$\text{Heart rate} = \frac{60}{15 \times 0.04} = 100\ \text{beats/min}$$

Q: A patient’s ECG shows an R-R interval of 25 mm. What is the heart rate? (1 mm = 0.04 s)

$$\text{Heart rate} = \frac{60}{25 \times 0.04} = 60\ \text{beats/min}$$

Q: Which of the following is the correct calculation for heart rate if the R-R interval is 0.8 seconds?

$$\text{Heart rate} = \frac{60}{0.8} = 75\ \text{beats/min}$$

Q: A patient’s ECG shows an R-R interval of 12 mm. What is the heart rate? (1 mm = 0.04 s)

$$\text{Heart rate} = \frac{60}{12 \times 0.04} = 125\ \text{beats/min}$$

Question 1

Which component of the heart's conduction system acts as the natural pacemaker and establishes the sinus rhythm?

Accepted Answer

Sinoatrial (SA) node

Question 2

What electrical event does the QRS complex on an ECG represent?

Accepted Answer

Ventricular depolarization

Question 3

If the R-R interval on an ECG is 20 mm, what is the duration of one cardiac cycle? (Each 1 mm = 0.04 s)

Accepted Answer

$$20 	imes 0.04 = 0.80\ 	ext{s}$$

Question 4

A patient’s ECG shows a heart rate of 120 beats/min. How would you classify this heart rate?

Accepted Answer

Tachycardia

Question 5

Which wave on the ECG corresponds to atrial systole?

Accepted Answer

P wave

Question 6

What is the correct sequence of electrical conduction through the heart?

Accepted Answer

SA node → AV node → AV bundle → Bundle branches → Purkinje fibers

Question 7

If the R-R interval is 15 mm on an ECG, what is the heart rate? (1 mm = 0.04 s)

Accepted Answer

$$	ext{Heart rate} = \frac{60}{15 	imes 0.04} = 100\ 	ext{beats/min}$$

Question 8

Which of the following best describes the mechanical event caused by the T wave on an ECG?

Accepted Answer

Ventricular diastole

Question 9

A 12-lead ECG uses how many electrodes and what is the main advantage of this setup?

Accepted Answer

10 electrodes; allows interpretation of specific areas of the heart

Question 10

Which interval on the ECG is most commonly used to calculate heart rate?

Accepted Answer

R-R interval

Question 11

A patient’s ECG shows an R-R interval of 25 mm. What is the heart rate? (1 mm = 0.04 s)

Accepted Answer

$$	ext{Heart rate} = \frac{60}{25 	imes 0.04} = 60\ 	ext{beats/min}$$

Question 12

Which of the following is NOT a component of the heart’s conduction system?

Accepted Answer

Mitral valve

Question 13

What is the primary purpose of placing electrodes on the limbs and chest during an ECG?

Accepted Answer

To record the electrical activity of the heart from different angles

Question 14

Which of the following best explains why atrial repolarization is not seen as a distinct wave on a standard ECG?

Accepted Answer

It occurs at the same time as ventricular depolarization and is masked by the QRS complex

Question 15

A patient’s ECG shows a heart rate of 55 beats/min. How would you classify this heart rate?

Accepted Answer

Bradycardia

Question 16

Which of the following is the correct calculation for heart rate if the R-R interval is 0.8 seconds?

Accepted Answer

$$	ext{Heart rate} = \frac{60}{0.8} = 75\ 	ext{beats/min}$$

Question 17

Which mechanical event immediately follows ventricular depolarization?

Accepted Answer

Ventricular systole

Question 18

Which of the following best describes the function of Purkinje fibers?

Accepted Answer

Transmit impulses to the ventricular myocardium for coordinated contraction

Question 19

A patient’s ECG shows an R-R interval of 12 mm. What is the heart rate? (1 mm = 0.04 s)

Accepted Answer

$$	ext{Heart rate} = \frac{60}{12 	imes 0.04} = 125\ 	ext{beats/min}$$

Question 20

Which of the following is a real-life clinical use of the ECG?

Accepted Answer

Diagnosing electrical conduction disorders in the heart

Conduction System of the Heart and Electrocardiogram (ECG/EKG): Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards