Q: Calculate the cardiac output (CO) for a patient with a heart rate (HR) of 80 bpm and a stroke volume (SV) of 70 ml/beat. Use the formula $$CO = HR \times SV.$$

$$CO = 80 \times 70 = 5600 ml/$$min

Question 1

Which component of the ECG corresponds to ventricular depolarization, and what is its physiological significance?

Accepted Answer

QRS complex; it represents ventricular depolarization and initiates ventricular systole

Question 2

A patient presents with a heart rate of 52 bpm and is otherwise healthy and athletic. Which ECG abnormality is most likely present, and what is the term for this condition?

Accepted Answer

Bradycardia; rate \u003c60 bpm

Question 3

Calculate the cardiac output (CO) for a patient with a heart rate (HR) of 80 bpm and a stroke volume (SV) of 70 ml/beat. Use the formula $$CO = HR 	imes SV.$$

Accepted Answer

$$CO = 80 	imes 70 = 5600 ml/$$min

Question 4

Which of the following best describes the physiological event that produces the first heart sound (S1)?

Accepted Answer

Closure of the AV valves at the beginning of ventricular systole

Question 5

A patient’s ECG shows an irregular interval between P, QRS, and T waves. Which condition is most likely present?

Accepted Answer

Arrhythmia

Question 6

Which of the following is a positive chronotropic agent, and what is its effect on heart rate?

Accepted Answer

Epinephrine; increase heart rate

Question 7

During which phase of the cardiac cycle does isovolumetric contraction occur, and what is happening to the heart valves?

Accepted Answer

Isovolumetric contraction; all valves are closed

Question 8

A patient’s ECG shows an extra systole with an inverted QRS complex, misshapen QRS and T, and absence of a P wave before the contraction. What is the most likely diagnosis?

Accepted Answer

Premature ventricular contraction (PVC)

Question 9

Which of the following best explains why both ventricles must eject the same amount of blood during each cardiac cycle?

Accepted Answer

To prevent blood pooling in the pulmonary or systemic circuits

Question 10

If a patient’s end diastolic volume (EDV) is 130 ml and their end systolic volume (ESV) is 60 ml, what is their stroke volume (SV)? Use the formula $$SV = EDV - ESV.$$

Accepted Answer

$$SV = 130 - 60 = 70 ml$$

Question 11

Which ECG abnormality is most likely to be caused by excessive caffeine intake, and what is its characteristic feature?

Accepted Answer

Premature ventricular contraction (PVC); extra systole

Question 12

Which of the following best describes the effect of baroreceptors on heart rate when blood pressure decreases?

Accepted Answer

Signals to increase heart rate

Question 13

A young adult male has an average heart rate of 68 bpm. Which of the following statements is most accurate?

Accepted Answer

This is within the normal range for young adult males

Question 14

Which of the following is a likely consequence of ventricular fibrillation as seen on an ECG?

Accepted Answer

No effective pumping action, leading to cardiac arrest

Question 15

Calculate the ejection fraction (EF) for a patient with an EDV of 120 ml and an SV of 72 ml. Use the formula $$EF = \frac{SV}{EDV} 	imes 100\%.$$

Accepted Answer

$$EF = \frac{72}{120} 	imes 100\% = 60\%$$

Question 16

Which of the following is NOT a factor that can increase heart rate?

Accepted Answer

Physical fitness

Question 17

A patient’s ECG shows no P waves and a slow, regular rhythm. Which abnormality is most likely present?

Accepted Answer

Nodal rhythm (no SA node activity)

Question 18

Which of the following best describes the T wave on an ECG?

Accepted Answer

Ventricular repolarization

Question 19

Which of the following scenarios would most likely result in tachycardia?

Accepted Answer

A resting heart rate of 105 bpm after drinking several energy drinks

Question 20

Which of the following best explains why chemoreceptors increase heart rate in response to elevated $$CO_2$$ levels?

Accepted Answer

To increase removal of carbon dioxide via increased blood flow

Chapter 18: Heart Part 2

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