Q: Which of the following is the correct formula for calculating heart rate from an EKG strip if the R-R interval is measured in seconds?

$$\text{Heart Rate} = \frac{60}{\text{R-R interval (seconds)}}$$

Q: A patient’s EKG shows a heart rate of 130 beats per minute, regular rhythm, and a P-wave before each QRS complex. Which formula would you use to calculate the cardiac output if the stroke volume is known?

$$\text{Cardiac Output} = \text{Heart Rate} \times \text{Stroke Volume}$$

Question 1

Which of the following best describes the EKG findings in a patient with atrial fibrillation?

Accepted Answer

Irregularly irregular rhythm with no discernible P-waves and presence of F-waves

Question 2

A 65-year-old male presents with chest pain. His EKG shows ST segment elevation in the inferior leads and reciprocal ST depression in the lateral leads. Which artery is most likely occluded?

Accepted Answer

Right coronary artery

Question 3

Which of the following is the defining EKG characteristic of a first-degree AV block?

Accepted Answer

Prolonged PR interval greater than 0.20 seconds

Question 4

A patient’s EKG shows a heart rate of 45 beats per minute, regular rhythm, and normal QRS morphology. Which arrhythmia is most likely present?

Accepted Answer

Bradycardia

Question 5

Which of the following best explains the mechanism of a third-degree AV block?

Accepted Answer

Complete dissociation between atrial and ventricular activity

Question 6

A patient’s EKG shows a regular rhythm, heart rate of 110 beats per minute, normal QRS morphology, and a P-wave before each QRS complex. What is the most likely diagnosis?

Accepted Answer

Sinus tachycardia

Question 7

Which of the following EKG findings is most characteristic of a second-degree AV block, Mobitz Type I (Wenckebach)?

Accepted Answer

Progressive prolongation of PR interval until a QRS complex is dropped

Question 8

A 72-year-old woman presents with palpitations. Her EKG shows no distinct P-waves, an irregularly irregular rhythm, and variable ventricular response. Which arrhythmia is most likely?

Accepted Answer

Atrial fibrillation

Question 9

Which of the following is the correct formula for calculating heart rate from an EKG strip if the R-R interval is measured in seconds?

Accepted Answer

$$	ext{Heart Rate} = \frac{60}{	ext{R-R interval (seconds)}}$$

Question 10

A patient’s EKG shows regular P-waves with a constant PR interval, but some QRS complexes are missing. Which arrhythmia does this describe?

Accepted Answer

Second-degree AV block, Mobitz Type II

Question 11

Which of the following is a hallmark EKG finding in an inferior myocardial infarction (MI)?

Accepted Answer

ST segment elevation in leads II, III, and aVF

Question 12

A 55-year-old man has an EKG with a PR interval of 0.24 seconds, regular rhythm, and a P-wave before each QRS complex. What is the most likely diagnosis?

Accepted Answer

First-degree AV block

Question 13

Which of the following best describes the electrical activity in the atria during atrial fibrillation?

Accepted Answer

Hundreds of sites in the atria fire with their own intrinsic rates

Question 14

A patient’s EKG shows a regular rhythm, heart rate of 80 beats per minute, and a PR interval of 0.28 seconds. What is the most likely diagnosis?

Accepted Answer

First-degree AV block

Question 15

Which of the following is the most appropriate initial treatment for symptomatic bradycardia due to a third-degree AV block?

Accepted Answer

Transcutaneous pacing

Question 16

A 60-year-old patient presents with dizziness. His EKG shows a regular atrial rhythm, but the ventricular rhythm is also regular and slower, with no relationship between P-waves and QRS complexes. What is the diagnosis?

Accepted Answer

Third-degree AV block

Question 17

Which of the following is the most likely consequence of untreated atrial fibrillation?

Accepted Answer

Increased risk of thromboembolic stroke

Question 18

A patient’s EKG shows a heart rate of 130 beats per minute, regular rhythm, and a P-wave before each QRS complex. Which formula would you use to calculate the cardiac output if the stroke volume is known?

Accepted Answer

$$	ext{Cardiac Output} = 	ext{Heart Rate} 	imes 	ext{Stroke Volume}$$

Question 19

Which of the following best describes the QRS morphology in normal sinus rhythm, tachycardia, and bradycardia?

Accepted Answer

QRS complexes are normal in all three rhythms

Question 20

A patient’s EKG shows progressive prolongation of the PR interval until a QRS complex is dropped. What is the most likely diagnosis?

Accepted Answer

Second-degree AV block, Mobitz I (Wenckebach)

EKG Rhythms: Normal and Abnormal Cardiac Conduction

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