ACSM-EP Cardiovascular Physiology — Questions and Answers
Question 1: A client has a resting blood pressure of 120/80 mmHg. What is the approximate mean arterial pressure (MAP)?
- 100 mmHg
- 80 mmHg
- 87 mmHg
- 93 mmHg (Correct answer)
Correct answer: 93 mmHg
MAP = DBP + 1/3(SBP - DBP) = 80 + 13 = about 93 mmHg.
MAP approximates the average driving pressure for organ perfusion and is calculated as DBP + 1/3 pulse pressure. Here pulse pressure is 120 - 80 = 40 mmHg, one-third is about 13, so MAP = 80 + 13 = 93 mmHg. Simply averaging 120 and 80 gives 100 mmHg, which overestimates MAP because diastole lasts longer than systole at resting heart rates. 80 mmHg is only the diastolic pressure and 87 mmHg would underestimate MAP.
Question 2: During peak exercise, cardiac output is 20 L/min and the arteriovenous oxygen difference is 15 mL O2 per 100 mL blood. According to the Fick equation, what is VO2?
- 1,500 mL/min
- 3,000 mL/min (Correct answer)
- 2,250 mL/min
- 4,500 mL/min
Correct answer: 3,000 mL/min
VO2 = Q x a-vO2 difference = 20 L/min x 150 mL O2/L = 3,000 mL/min.
The Fick equation states VO2 = cardiac output x (a-vO2 difference). An a-vO2 difference of 15 mL per 100 mL equals 150 mL per liter. Multiplying 20 L/min x 150 mL/L gives 3,000 mL/min (3.0 L/min). The other options come from unit errors, such as forgetting to convert per 100 mL to per liter (giving 300 or 30) or using the wrong factor. This relationship shows that both central delivery (cardiac output) and peripheral extraction determine VO2max.
Question 3: Which blood pressure response is normal during a graded treadmill exercise test in a healthy adult?
- Systolic rises progressively while diastolic stays the same or changes slightly (Correct answer)
- Systolic falls progressively while diastolic rises
- Both systolic and diastolic rise by about 10 mmHg per MET
- Systolic stays constant while diastolic rises sharply
Correct answer: Systolic rises progressively while diastolic stays the same or changes slightly
Systolic BP rises progressively (about 10 mmHg per MET) while diastolic stays about the same or changes by 10 mmHg or less.
During dynamic aerobic exercise, cardiac output rises, so systolic pressure increases by roughly 10 mmHg per MET, whereas diastolic pressure stays near resting values or changes by no more than about 10 mmHg because working muscle vasodilates and lowers total peripheral resistance. A falling systolic pressure with increasing workload is abnormal and is an indication to stop the test. A sharply rising diastolic pressure (for example above 110 mmHg) is also abnormal and a relative reason to terminate.
Question 4: During a cycling session, a client has a heart rate of 140 bpm and a systolic blood pressure of 160 mmHg. What is the rate-pressure product, and what does it estimate?
- 22,400; myocardial oxygen demand (Correct answer)
- 300; stroke volume
- 2,240; cardiac output
- 20,000; mean arterial pressure
Correct answer: 22,400; myocardial oxygen demand
RPP = HR x SBP = 140 x 160 = 22,400, an index of myocardial oxygen demand.
Rate-pressure product (double product) equals heart rate times systolic blood pressure: 140 x 160 = 22,400. It is a noninvasive estimate of myocardial oxygen consumption and is useful in clients with coronary artery disease because the heart rate or RPP at which angina or ischemia appears is reproducible. Adding the values (300) does not give a meaningful index, and RPP does not measure stroke volume, cardiac output, or MAP.
Question 5: After 12 weeks of endurance training, a client performs the same absolute submaximal workload as before. Which change is expected?
- Higher heart rate and lower stroke volume
- Lower heart rate and higher stroke volume (Correct answer)
- Higher heart rate and unchanged cardiac output
- Unchanged heart rate and lower cardiac output
Correct answer: Lower heart rate and higher stroke volume
At the same submaximal workload, trained individuals have a lower heart rate and a higher stroke volume, with cardiac output about unchanged.
Submaximal oxygen demand at a fixed workload is the same, so cardiac output is about the same before and after training. Training increases blood volume and ventricular filling and augments contractility, which raises stroke volume, and increased vagal tone lowers heart rate. Since cardiac output equals heart rate times stroke volume, a higher stroke volume allows a lower heart rate. The reverse pattern (higher heart rate, lower stroke volume) is typical of deconditioning.
Question 6: The left ventricle receives most of its coronary blood flow during which phase of the cardiac cycle?
- Isovolumetric contraction
- Ventricular ejection
- Diastole (Correct answer)
- Atrial systole only
Correct answer: Diastole
The left ventricle is perfused mainly during diastole because systolic contraction compresses the intramyocardial vessels.
During systole the contracting left ventricular wall squeezes the intramural coronary vessels and limits flow. Perfusion therefore occurs mainly in diastole, driven by the aortic diastolic pressure. This explains why very high heart rates, which shorten diastole, can reduce coronary perfusion time and provoke ischemia in people with coronary artery disease. Ejection is the period of greatest compression, not the period of greatest flow.
