Pediatric Cardiology Board Review

Chapter 7. Exercise Physiology and Testing

Justin M. Horner

   1. What is the most commonly accepted method of indexing maximum oxygen uptake () in clinical exercise testing?

A. Age

B. Sex

C. Lean body mass

D. Body weight (kilograms)

E. Exponent of body length

   2. Which method of exercise would achieve a higher maximum oxygen uptake ()?

A. Stationary electronically braked cycle ergometer

B. Arm crank ergometer

C. Hand grip ergometer

D. Treadmill ergometer

E. Stationary mechanically braked cycle ergometer

   3. Which cardiac exercise parameter has a limited increase in with exercise in the supine position early in exercise?

A. Heart rate

B. Minute ventilation

C. Stroke volume

D. Respiratory rate

E. Blood pressure

   4. What cardiovascular changes would be expected during exercise?

   5. Which blood pressure change would be expected in a normal 15-year-old male patient (resting blood pressure = 110/72 mm Hg) with isotonic exercise?

A. 150/78 mm Hg

B. 155/55 mm Hg

C. 120/95 mm Hg

D. 170/100 mm Hg

E. 160/110 mm Hg

   6. Which blood pressure change would be expected in a normal 15-year-old male patient (resting blood pressure = 110/72 mm Hg) with isometric exercise?

A. 150/72 mm Hg

B. 170/60 mm Hg

C. 120/68 mm Hg

D. 220/100 mm Hg

E. 220/70 mm Hg

   7. What maximum heart rate and maximum oxygen consumption would best represent a normal 15-year-old male patient during isotonic exercise?

   8. A healthy 21-year-old female on no medications just finished a treadmill exercise test. She exercised for a total of 6 minutes. The exercise physiologist technician questioned her effort. However, the patient claimed she “gave it her all.” What is her expected maximal heart rate?

A. 123 bpm

B. 158 bpm

C. 185 bpm

D. 189 bpm

E. 196 bpm

   9. As a normal child ages, what ventilatory changes at peak exercise would be expected?

 10. What cardiovascular physiological changes would be expected with improved fitness? [COMP: Please align the below answers as given below]

 11. What physiological respiratory changes would be expected with improved fitness?

 12. Which condition would be a contraindication for exercise testing?

A. Atrial septal defect with left-to-right shunt

B. Ventricular septal defect with left-to-right shunt

C. Severe primary pulmonary hypertension

D. History of myocardial infarction

E. History of rheumatic heart disease

 13. Compared with the normal population, highly trained adult athletes have which of the following physiologic changes?

A. Decreased glycogen stores

B. Decreased oxidative enzyme activity

C. Increased minimum lactate

D. Decreased anaerobic enzyme activity

E. Increased triglyceride stores

 14. Identify the correct statement regarding ventilatory (anaerobic) threshold (VAT).

A. The VAT is the  at which there is a disproportionate decrease in minute ventilation relative to oxygen uptake

B. VAT is synonymous with the threshold for decompensated acidosis

C. There is commonly a relative drop in lactate production when VAT is reached

D. When VAT is reached, there is a decrease in mixed expired O2 concentration

E. During incremental exercise, VAT does not reflect the onset of anaerobic metabolism

 15. As compared to an acyanotic patient, an unrepaired, cyanotic patient at peak exercise will exhibit a higher:

A. Heart rate

B. Ventilatory equivalent for oxygen

C. Blood oxygen saturation

D. Maximum oxygen uptake

E. Diastolic blood pressure

 16. Which statement is correct regarding an optimal exercise protocol?

A. Duration of exercise test between 12 and 15 min

B. Modified Bruce protocol is appropriate for children with limited exercise capacity

C. James protocol has relatively small work increments

D. Ramp protocol has large increases in workload

E. Ramp protocol is appropriate for assessing steady-state exercise

 17. Which statement is correct regarding the ventilatory response to exercise?

A. Total ventilation increases because of increased rate, while tidal volume remains constant

B. Tidal volume increases predominately by tapping into the expiratory reserve volume

C.  declines early in exercise as a result of better ventilation and blood flow matching in the lungs

D. Normal subjects terminate exercise because ventilation can increase no further while cardiac output can continue to increase

E. Diffusion limitation is a common problem during routine clinical exercise testing

 18. Which of the following exercise testing technique statements would be correct?

A. Circling 60% of the patient’s arm with the sphygmomanometer cuff

B. Sphygmomanometer cuff width equals 30% of the upper arm length

C. Using the assumption that acetylene-helium technique approximates cardiac output in a patient with a large atrial septal defect and left-to-right shunt

D. Recognizing that acetylene-helium technique is dependent on even distribution of inspired gas in the lungs

E. Using CO2 rebreathing technique in children due to better toleration than acetylene-helium technique

 19. A 22-year-old male, well-trained college football athlete underwent a treadmill exercise study mid-season. Shortly thereafter, he sustained a lower limb injuring and was unable to train for 3 months during recovery. He now underwent a second treadmill exercise test at the start of re-training. Both exercise studies were maximum effort. Which data would best describe his situation?

 20. In a healthy 15-year-old female without lung disease who gave maximum effort on spirometry before exercise testing, which statement about maximum voluntary ventilation (MVV) is correct?

A. MVV is reliably measured as it is independent of subject effort

B. Maximal  < 70% of resting MVV suggests pulmonary limitation to exercise

C. MVV is ~35 to 40 times FEV1

D. MVV is typically measured during early exercise

E. MVV can also detect vocal cord dysfunction as a cause for exertional dyspnea

 21. In healthy patients, which of the following is a normal physiological response during exercise?

A. Increased end-systolic volume

B. Increased diastolic pressure during isotonic exercise

C. Among similar-sized children, girls have a higher peak systolic blood pressure than boys

D. Black children have a greater blood pressure response to exercise when compared to white children

E. Blood pressure increases during exercise are due to increased systemic resistance

 22. Which patient would be a good candidate for the use of acetylene-helium rebreathing technique during exercise testing for the measurement of cardiac output?

A. 15-year-old male with Epstein’s anomaly and a large secundum ASD with right-to-left shunt

B. 12-year-old female s/p Fontan operation with AV pulmonary fistulas

C. 14-year-old male with a patent foramen ovale with trivial left-to-right shunt

D. 8-year-old male with a moderate membranous VSD with left-to-right shunt

E. 10-year-old female with a persistent left SVC and unroofed coronary sinus

 23. During exercise stress testing, what direct measurement can be determined by using acetylene helium rebreathing technique?

A. Systemic blood flow

B. Pulmonary oxygen exchange

C. Cardiac output

D. Shunt volume

E. Effective pulmonary blood flow

 24. In a healthy, normal child, what organ system is most commonly responsible for limiting maximal achievable workload?

A. Pulmonary

B. Cardiovascular

C. Musculoskeletal

D. Neurologic

E. Gastrointestinal

 25. The calculation of work can be completed with which equation?

A. Work = force × distance

B. Work = force/distance

C. Work = distance/force

D. Work = mass × acceleration

E. Work = mass/acceleration

 26. Which statement about exercise testing physiology is correct?

A. An increase in stroke volume is the major determinant of an increased cardiac output during exercise in a normal patient

B. Girls, particularly after puberty, have a slightly lower heart rate when compared to boys at any given workload

C. For patients >20 years of age, maximal heart rate changes with age

D. For patients >20 years of age, maximum heart rate increase with conditioning

E. Total systemic vascular resistance increases with increase workload

 27. Which of the following patients, if a maximal effort was achieved, would result in a higher maximal  during work?

A. A 17-year-old white, female who completed cycle exercise testing

B. A 17-year-old white, male who completed cycle exercise testing

C. An 18-year-old white, anemic, male who completed cycle exercise testing

D. A 12-year-old African-American, male who completed cycle exercise testing

E. A 12-year-old African-American, female who completed cycle exercise testing

 28. Which of the following echocardiographic findings would be most consistent with a heart of a well-trained, normal athlete?

A. Decreased left ventricular end-diastolic dimension

B. Decreased left ventricular wall thickness

C. Decreased stroke volume

D. Increased left ventricular end-diastolic volume

E. Increased left ventricular end-systolic dimension

 29. Which of the following conditions is an absolute contraindication to exercise testing?

A. Second-degree A-V block

B. Severe aortic stenosis

C. Catecholaminergic polymorphic ventricular tachycardia

D. Long QT syndrome

E. Anomalous origin of a coronary artery

 30. Which of the following statements comparing treadmill exercise testing to cycle ergometry is correct?

A. Cycle ergometry derived maximum oxygen uptake () is higher than treadmill testing

B. Noise and artifact is less during treadmill exercise testing

C. Cycle ergometry allows for a more accurate work measurement

D. Cycle ergometry is potentially more dangerous than treadmill ergometry

E. Younger children (4 to 6 years of age) may have more difficulty using a treadmill ergometry than a cycle ergometry

 31. Which statement is most accurate with regard to aortic stenosis and exercise stress testing?

A. Total work performed has a linear relationship with transaortic pressure gradient

B. Greater increase in systolic blood pressure with exercise when compared to normal patients

C. The higher the transaortic gradient, the lower expected ST segment change during exercise

D. The higher the transaortic gradient, the higher the maximum oxygen uptake () achievable

E. Total work performed has an inverse relationship with transaortic pressure gradient

 32. Which exercise testing statement would be most correct in an 8-year-old male with a systemic-to-pulmonary anastomosis with pulmonary atresia and ventricular septal defect?

A. Achievement of normally expected maximum aerobic power

B. Normal ventilation relative to maximal oxygen uptake ()

C. Blood oxygen saturation improves with exercise

D. Complete repair would improve the blood oxygen saturation with exercise

E. Complete repair would improve exercise time to be comparable to normal patients

 33. Which statement is consistent with an appropriate exercise technique?

A. Only two surface electrocardiogram (ECG) leads need to be recorded during the exercise study

B. A complete 12-lead ECG should be obtained once at rest, at each workload, and several times after completion

C. The use of skin cleanser, electrode paste, and lead bandaging is necessary for treadmill ergometry but unnecessary for cycle ergometry

D. Diastolic blood pressure measurement is typically made with ease during treadmill ergometry

E. Direct blood pressure measurement in the radial artery underestimates the central aortic blood pressure

 34. During an exercise study, which statement is consistent with an appropriate ventilation measurement?

A. End-tidal CO2 cannot be directly measured and only estimated

B. Measurement of ventilatory indices, using a respiratory mass flow sensor, does not require a patient nose clip and mouthpiece or tightly fitting mask

C. Blood oxygen saturation by oximetry has a reliable correlation with direct blood gas analysis for saturation levels >75%

D. Ventilatory equivalent for O2 can be directly measured

E. Ventilatory equivalent for CO2 can be directly measured

 35. Using the CO2 rebreathing technique during an exercise study, which statement is most correct?

A. The CO2 rebreathing technique is well tolerated by all patients and is noninvasive

B. The CO2 concentration in the rebreathing technique does not need to be adjusted for the patient’s size and exercise intensity

C. The CO2 rebreathing technique does not obtain enough information to use the Fick principle for determining the cardiac output

D. Accounting for instrument dead space while using the CO2 rebreathing technique will greatly overestimate cardiac output measurements

E. The CO2 rebreathing technique can be completed noninvasively by using the Bohr equation

ANSWERS

1. ANSWER: D.  Maximum oxygen uptake is closely related with cardiac output. The more work/exercise a patient does the more oxygen uptake will be needed. This increased oxygen demand is supplied by increasing the uptake for the increased muscle groups being used. Many methods for indexing  have been suggested but a constant is hard to accomplish. Males tend to have a higher lean body mass than females, which causes differences in  between the sexes.  also changes with increasing age. Previous studies have revealed an exponent of body length (1.5 to 3.21) has also been unreliable. The most commonly accepted method of indexing  is body weight. It has been shown to possess a relatively constant method of indexing in older childhood/early adolescent males and females and seems to be the method with the least limitations.

2. ANSWER: D.  The maximum  that can be achieved depends on the type of work performed. The more muscle mass used will require more oxygen supplementation in order for those muscle groups to continue to perform. Therefore, the  would be considerably higher for the treadmill exercise test (running = the use of many different/whole body muscle groups) versus the other types of exercise testing listed that only use select muscle groups.

3. ANSWER: C.  Stroke volume is dependent on left ventricular end-diastolic volume and ejection fraction. In the supine position, stroke volume will increase normally due to increased volume return (increased end-diastolic volume) to the heart. Thus, the stroke volume is already increased from baseline, and the volume needed to reach maximum stroke volume will be small and limited. Finally, stroke volume primarily increases early in exercise and will increase little thereafter. Bodily position will not limit the increase of the other parameters listed in the same extent as stroke volume.

4. ANSWER: D.  In the normal patient, exercise will cause an increase in cardiac output, heart rate, and ejection fraction. A decrease in the total peripheral resistance will occur, and no change will be seen in the central venous pressure. These changes are primarily due to the large increase in sympathetic activity during exercise. As the exercise/work is increased, the muscle groups will increase their oxygen uptake. Therefore, the cardiac output (heart rate × stroke volume) will increase to deliver more oxygen to the working muscles. The decreased total peripheral resistance is primarily due to a decreased skeletal muscle vascular resistance allowing more blood flow to the muscles. Finally, the central venous pressure remains relatively unchanged due to the compensatory mechanisms of the skeletal muscle pump and the respiratory pump that both promote increased venous return and thus no need to increase the central venous pressure.

5. ANSWER: A.  Isotonic exercise is typical of most exercise. It consists of muscle length changes against a force/tension. During isotonic exercise, systolic blood pressure increases. However, diastolic blood pressure remains relatively unchanged (within 10 mm Hg of resting diastolic pressure). Blood pressure changes depend on patient size as well as gender. Larger patients and/or males will have a higher blood pressure at rest and during exercise compared to smaller patients and/or females. The systolic blood pressure increase during exercise is attributed to increased cardiac output despite a reduction in total systemic resistance.

6. ANSWER: D.  Isometric exercise consists of constant muscle length (no change) against a force/tension. Examples include holding a weight in a fixed position or pushing against a door frame. During isometric exercise, systolic and diastolic blood pressure increase significantly. Blood pressure changes depend on patient size as well as gender. Larger patients and/or males will have a higher blood pressure at rest and during exercise compared to smaller patients and/or females.

7. ANSWER: A.  Normal patients will rely on heart rate increase as the major determinant to increase their cardiac output. There is a linear relationship between heart rate and . Each individual has a maximum heart rate that is achievable; usually ranging between 195 and 215 bpm in children. Normal oxygen consumption () is considered to be roughly 2.5 L/min. Therefore, a heart rate of 200 bpm and oxygen consumption of 2.5 L/min would represent a normal patient. Heart rate of 145 bpm and oxygen consumption of 1.0 L/min would represent a submaximal exercise test/effort. Heart rate of 190 bpm and oxygen consumption 1.5 L/min, or 200 bpm and 3.5 L/min would represent a deconditioned patient. Heart rate of 190 bpm and oxygen consumption of 1.0 L/min would represent a highly conditioned patient. The typical graph representing the relationship between heart rate and oxygen consumption is seen in Figure 7.1., with A being the correctly labeled graph.

Figure 7.1.

8. ANSWER: E.  Heart rate maximum is an important determinant of . The accepted heart rate maximum for patients 5 to 20 years of age is roughly 195 to 215 bpm. However, for patients >20 years of age, the equation (HRmax = 210 – 0.65 × age) is the accepted method of determining heart rate maximum for each individual. Therefore, this patient’s heart rate maximum is 196 bpm (HRmax = 210 – 0.65 × 21). Heart rate maximum will vary with exercise ergometry; treadmill allowing for a slightly higher heart rate than cycle exercise testing, for example.

9. ANSWER: B.  During exercise/work, minute ventilation increases. This occurs by an increase in both ventilation frequency and tidal volume. These parameters will continue to increase with increasing age. However, the maximum respiratory rate that can be achieved during peak exercise will decrease with increasing age.

10. ANSWER: E.  Repetitive exercise will usually result in improved fitness. As patients become fit, they can increase the work completed or in other words increase their  maximum. Physiologic changes that occur with improved fitness include a decreased resting heart rate and increased stroke volume and cardiac output. With conditioning, the decrease in resting heart rate is likely due to increased stroke volume as well as increased vagal influence at rest. There is no change to heart rate maximum with improved fitness. However, a patient’s heart rate maximum will decrease with increasing age.

11. ANSWER: A.  With improved fitness, physiological respiratory changes will occur. Similar to a decreased resting heart rate with improved fitness, the resting respiratory rate will also decrease and, in turn, decrease the resting minute ventilation. On the contrary, the maximum minute ventilation will increase as well as the maximum tidal volume.

12. ANSWER: C.  Of the answers listed, the only contraindication to exercise testing would be severe primary pulmonary hypertension. An atrial septal defect would not be a contraindication to exercise testing. They are relatively common, 5% to 10% of the population, and a left-to-right shunt would not cause increased hypoxia with exercise. The same would hold true for a ventricular septal defect. An acute myocardial infarction or acute rheumatic heart disease would both be contraindications to exercise testing due to fragile myocardial tissue. However, a history of either of these disease processes would be an indication for exercise testing especially with symptoms of fatigue and/or exercise intolerance.

13. ANSWER: E.  With improved fitness, an athlete’s muscle metabolism improves through many mechanisms. The muscles will increase the number and volume of mitochondria. They will increase the stores and utilization of glycogen and triglycerides. ATP content and utilization will increase along with an increase in myoglobin. Oxidative enzyme activity and anaerobic enzyme activity both increase; in turn, an increased maximum lactate. Finally, creatine phosphate also increases.

14. ANSWER: E.  The VAT occurs at the point of exercise when there is a disproportionate increase in minute ventilation () relative to oxygen uptake. This results in an increased expiration of mixed oxygen concentration. In adults, a disproportionate increase in lactate is also frequently observed. However, this is not necessary for the change in  to occur. Therefore, it does not reflect the onset of anaerobic metabolism and thus, the “old name” of anaerobic threshold is better stated as the VAT. Decompensated acidosis is not synonymous with VAT. Decompensated acidosis occurs later in exercise, after the VAT has occurred, as the  increases disproportionately to CO2production and a reduction in PaCO2 and end-tidal CO2.

15. ANSWER: B.  The ventilatory equivalent for oxygen is minute ventilation divided by oxygen uptake (). Therefore, patients with cyanotic heart disease typically have hypoxemia at rest and during exercise than acyanotic patients. The presence of a large right-to-left shunt is a major determinant of this abnormal exercise response. At peak exercise, the cyanotic patient increases their minute ventilation () disproportionately to their oxygen uptake (), resulting in a higher ventilatory equivalent for oxygen than the acyanotic patient. The blood oxygen saturation and maximum oxygen uptake () will be lower. The heart rate and diastolic blood pressure should not change any differently than the acyanotic patient.

16. ANSWER: B.  There is no one “best” exercise protocol. However, in general, a “good” exercise protocol should have nonexcessive increments of work load with a duration lasting no longer than 8 to 12 min. The Bruce treadmill protocol and/or the “modified” Bruce protocol are popular with children and those individuals incapable of long exercise due to smaller, frequent increases of work load. The James protocol involved cycle ergometry as well as relatively large increments of work load. The ramp treadmill protocol is becoming more and more popular due to a constantly increasing work load. This test’s work load can be adjusted in order to have the test last 8 to 10 minutes. However, this protocol will not allow assessment of steady-state exercise due to the constant changing work load.

17. ANSWER: C.  Early in exercise, a patient will decrease their / due to better ventilation than at rest and by improved ventilation and blood flow matching particularly in the apices of the lungs. With increased work, the ventilatory response includes increased minute ventilation (), respiratory rate, and tidal volume. As a child grows, the maximum respiratory rate that can be achieved decreases, but the tidal volume and  increases. Tidal volume increases by slightly encroaching into the expiratory reserve volume, however, it predominately increases by tapping into the inspiratory reserve volume. Normal patients terminate exercise because cardiac output can no longer increase even though there typically is still ventilatory reserve available. Diffusion limitation is rarely a problem during routine clinical exercise testing. It could be hypothesized for this to occur in a highly trained athlete where the transit time of blood through the capillaries is too short to allow adequate gas exchange.

18. ANSWER: D.  Acetylene-helium rebreathing technique is used to measure cardiac output indirectly by measuring effective pulmonary blood flow in the absence of significant intracardiac shunts. This technique is also dependent on even distribution of the inspired gas throughout the lungs. It will not be a reliable method for cardiac output measurement in patients with lung disease that involves mismatching of ventilation and perfusion. The sphygmomanometer cuff should have a bladder length that should cover at least 80% of the circumference of the upper arm and at least 40% width of the upper arm.

19. ANSWER: B.  With improved fitness, a patient can complete more work; thus, a higher aerobic power (maximum ) is achieved. Maximum minute ventilation () also increases with improved fitness. During a maximal effort exercise study, the patient’s ability to reach maximum heart rate and maximum blood pressure will not be limited due to the time of deconditioning. The oxygen saturation should not be low during an exercise test in a highly trained athlete as well as it should not improve with deconditioning.

20. ANSWER: C.  MVV is obtained at rest, and it is greatly dependent on the patient’s effort. MVV has been shown to be ~35 to 40 times 1-s forced expiratory volume (FEV1). Owing to the dependence on the patient’s effort, MVV must cautiously be used for suggesting pulmonary limitation. At the point of exercise termination in a normal patient, minute ventilation () is 60% to 70% of MVV. Patients with lung disease and pulmonary limitation will achieve a  >70% by tapping into the ventilatory reserve. Tidal flow-volume loops have been shown to be a more accurate method to assessing pulmonary limitation to exercise than MVV. It also has the advantage of assessing for vocal cord dysfunction, which is an increasingly common cause for exertional dyspnea.

21. ANSWER: D.  Black children have a greater blood pressure response to exercise than white children. The same holds true for larger-sized children when compared to smaller-sized children. Of similar-sized patients, boys have a greater blood pressure response than girls. During exercise, the cardiac output will increase by increasing stroke volume as well as heart rate. Therefore, the end-systolic volume will decrease. During isotonic exercise, the diastolic pressure remains relatively stable (change < 10 mm Hg); however, during isometric exercise the diastolic blood pressure increases. Blood pressure increases during exercise predominately occur by increased cardiac output. The total systemic resistance decreases during exercise.

22. ANSWER: C.  Acetylene-helium rebreathing technique, which is dependent on even distribution of the inspired gas throughout the lungs, is used to measure cardiac output indirectly by measuring effective pulmonary blood flow in the absence of significant intracardiac shunts. It will not be a reliable method of cardiac output measurement in patients with lung disease that involves mismatching of ventilation and perfusion or those patients with significant intracardiac or intrapulmonary shunts. Therefore, the only patient with an insignificant intracardiac shunt of those listed would be the 14-year-old male with a patent foramen ovale with trivial left-to-right shunt.

23. ANSWER: E.  Acetylene-helium rebreathing technique is noninvasive, and it is usually well tolerated by children. This method directly measures the effective pulmonary blood flow in the absence of significant intrapulmonary or intracardiac shunts. This allows for an effective method to estimated cardiac output with the understanding that it will typically underestimate the cardiac output by 7% to 10%. The acetylene diffuses from the alveolus to the pulmonary capillary blood, and thus, the acetylene volume declines relative to the volume of effective pulmonary blood flow. This technique depends on an even distribution throughout the lungs.

24. ANSWER: B.  In the normal, healthy child, the cardiovascular organ system will most commonly be the limiting factor to maximal achievable workload. The maximum cardiac output will be achieved when the maximum heart rate limits ventricular filling during diastole and in turn stroke volume. On average, stroke volume increases level off at ~30% to 40% beyond maximum oxygen uptake (). Well-fit patients can continue to exrcise at their heart rate maximum for 1 to 2 min. The pulmonary organ system, in a normal, healthy child, will not most commonly limit maximal workload. Minute ventilation () and work have a linear relationship until the VAT is achieved. At this point, there is a disproportionate increase in  relative to . As exercise continues,  maintains a linear relationship with carbon dioxide output () until  rises disproportionately to . This point is known as the respiratory compensation point; which is characterized by hyperventilation and a reduction in PaCO2 and end-tidal pCO2 is noted. At the maximal point of exhaustion,  is 60% to 70% of maximum ventilation volume. Thus, the pulmonary organ system will continue to provide gas exchange. The musculoskeletal, neurologic, and gastrointestinal organ systems will not be the most common organ systems to limit a maximal exercise effort.

25. ANSWER: A.  A few equations for exercise are needed to calculate the total work accomplished as well as the total power achieved. Work is defined by force multiplied by distance or, in other words, the force needed to move a mass a given distance. The unit for work is the Newton-meter or joule (J). Force is mass × acceleration. Power is the work performed per unit of time. The other equations listed are not correct.

26. ANSWER: C.  For patients between the ages of 5 and 20, the estimated heart rate max has been stated to be ~195 to 215 bpm. For patients >20 years of age, the maximum heart rate will decrease with increasing age. A commonly accepted equation to determine a patient’s maximum heart rate is: heart rate maximum = 210 –(0.65 × age). The reason for this decline in heart rate maximum is unclear but may be due to fibrosis and scarring of the sinoatrial node. Females will typically have a slightly larger heart rate than males, particularly after puberty. Stroke volume increases during exercise occur early in exercise with little change thereafter. The heart rate increases then account predominately for increasing cardiac output. Systolic blood pressure will increase with isotonic exercise while the diastolic blood pressure remains relatively unchanged. With isometric exercise, both systolic and diastolic blood pressures will rise. However, with exercise, the total systemic vascular resistance declines.

27. ANSWER: B.  Maximal  achieved is dependent on age, sex, ethnicity, hemoglobin level, and type of work completed. As age increases in childhood, the maximal  achievable also increases. Between the sexes, the maximal  achievable is relatively the same before puberty, but thereafter, males have a higher . African-American patients have been shown to have lower maximal  when compared to white children or similar size. This has been thought to be due to slightly smaller lung volumes and lower hemoglobin levels. Anemic patients have a lower achievable  than normal hemoglobin patients. Finally, achievable  depends on the type of work completed; the more muscle groups involved, the higher the  achievable. Therefore, a higher  is achieved with treadmill ergometry > cycle ergometry > arm crank ergometry > hand grip ergometry. Therefore, the older, nonanemic male would achieve the highest  during cycle exercise testing.

28. ANSWER: D.  A well-trained, normal athlete heart will undergo certain changes. The resting heart rate will decrease while the stroke volume at rest and at maximum heart rate will increase. Therefore, the cardiac output will increase at maximum heart rate. On echocardiography, an increased left ventricular end-diastolic dimension/volume will be noted. A decreased left ventricular end-systolic dimension/volume will occur. With increasing fitness, the left ventricular wall thickness will increase.

29. ANSWER: B.  Of the answers listed, the only contraindication to exercise testing would be severe aortic stenosis. Known exercise-induced arrhythmias can be relative contraindications; however, exercise testing is a useful provocative test as in catecholaminergic polymorphic ventricular tachycardia and long QT syndrome. Therefore, exercise testing can be carried out in these patients. First- and second-degree AV block would not be absolute contraindications to exercise testing. Finally, anomalous origin of the right coronary artery would not be an absolute contraindication to exercise testing. However, exercise stress testing would be helpful in the assessment of an anomalous coronary for exercise induced angina, etc.

30. ANSWER: C.  Neither treadmill nor cycle ergometry is superior to the other. However, there are advantages and disadvantages to each type. Treadmill ergometry will allow a patient to derive a higher  due to the use of more muscle groups during exercise. Also, most people, even very young children, can walk efficiently but not all can cycle efficiently. However, the treadmill ergometers are potentially more dangerous due to the potential of the patient falling and there is more noise and artifact while running when compared to stationary cycling. A more accurate and controlled measurement of work can be obtained with cycle ergometry. This is due to work/power changes are more easily accomplished and recorded with a mechanically or electronically braked cycle ergometer when compared to a treadmill ergometer. However, this will also depend on the exercise protocol used.

31. ANSWER: E.  Exercise testing in aortic stenosis patients can be helpful in the assessment of mild to moderate stenosis for significant ST segment changes with exercise as well as distinguishing between chest wall pain and more significant causes of chest pain. In aortic stenosis, there is an inverse relationship between the total work performed and transaortic pressure gradient. Also, patients with more severe aortic stenosis (i.e., higher transaortic gradient) have a lower increase in their blood pressure response during exercise than less severe aortic stenosis patients. It has also been shown that the higher the transaortic gradient the more likely the expected ST segment changes to occur. Finally, it has been shown that the patients with more severe aortic stenosis achieved a lower .

32. ANSWER: D.  Unrepaired single ventricle patients will have reduced maximum aerobic power and excessive ventilation relative to . Specifically, unrepaired patients with pulmonary atresia with VSD have decreased total work, maximal power achieved, exercise time and maximal oxygen uptake when compared to first stage or complete repair patients as well as normal patients. Blood oxygen saturation levels in unrepaired and first stage repaired patients are lower at rest than normal patients and decrease significantly with exercise. Complete repair patients will have a relatively normal resting blood oxygen saturation level and will have little decrease with exercise. This is similar to normal, healthy patients who may have little to no decrease with exercise.

33. ANSWER: B.  A complete 12-lead ECG should be obtained once at rest, at each workload, and several times after completion. A typical recording includes at rest sitting, supine, and standing; then at each workload and peak exercise, as well as each minute (1 to 5) of recovery. At least three standard surface ECG leads should be continuously displayed and recorded during the exercise study as well as for 5 to 10 min after the study is completed. The operator should have the option of switching between various combinations of those leads (i.e., inferior leads, anterior right, anterior left, etc.). Appropriate ECG electrode and lead placement should be used in all types of ergometry to limit artifact. This includes skin cleansing and abrading, electrode paste use, and ECG lead cable securing with an elastic band/knit shirt. Owing to the typical artifact with treadmill exercise testing, the Korotkoff sounds, especially diastolic, can be very difficult to measure accurately. Direct blood pressure measurement, through arterial access, in the peripheral arteries will overestimate the central aortic pressure due to peripheral amplification.

34. ANSWER: C.  Blood oxygen saturation measurements can be made noninvasively with the use of the ear or finger oximetry. It has been shown to have excellent correlation with oxygen saturations >75% and less so as the oxygen saturation decreases. Using a respiratory mass flow sensors and high-speed gas analyzers, the ventilatory indices that can be directly measured include respiratory rate, tidal volume, minute ventilation, oxygen uptake CO2production, end-tidal CO2 and O2, and mixed expired CO2 and O2. Appropriate measurement of ventilatory indices includes the use of a patient nose clip and mouthpiece or tight fitting mask for a closed system. Ventilatory equivalents for O2 () and CO2 () and respiratory gas-exchange ratio can be determined.

35. ANSWER: E.  The CO2 rebreathing technique is one of two of the most frequently used techniques (other = acetylene-helium rebreathing technique) for measuring cardiac input noninvasively. The CO2 rebreathing technique is based on the Fick principle for CO2 {Cardiac output = /[CvCO2(mixed venous CO2)-CaCO2(systemic arterial CO2)]}. However, arterial CO2 content needs to be directly measured from systemic arterial blood pCO2 or, noninvasively, by estimating this by using the Bohr equation. This is accomplished by solving for PaCO2 (systemic arterial pCO2): VD/VT = (PaCO2 – PeCO2)/PaCO2. This technique is not well-tolerated by all, especially children, due to the rebreathing of CO2 can cause dyspnea, an unpleasant taste, and a transient headache. This technique involves a few areas of potential error. These include the need to adjust CO2 concentration used for the patient’s size and exercise intensity as well as taking into account the dead space (mouthpiece, etc.).