Question

You are performing a CPET on a 57 year old male who sustained an anterior wall MI (heart attack) at age 55. His doctor would like you to evaluate his cardiorespiratory fitness and cardiovascular responses to physical activity in response to his recent complaints of shortness of breath. He is on blood pressure medication, but not of the type which limits his Heart Rate at rest or with exercise. The CPET is terminated after 6 minutes due to a 30mmHg drop in systolic blood pressure, a drop in the O₂ pulse from 7ml/beat at minute 5 to 3ml/beat at minute 6 combined with an increased reporting of chest discomfort/shortness of breath.

Which of the following statements is/are true?
A. Because the O₂ pulse dropped from 7ml/beat to 3ml/beat you suspect his stroke volume began to decrease which may be causing his chest discomfort.
B. Cardiac output will begin to drop with the decreasing O₂ pulse thereby resulting in his drop in systolic BP, unless compensatory changes occur.
C. It would not be unusual to observe a sharp decrease in the HR - VO2 relationship to compensate for a decreased SV.
D. Both (A) and (B) are true.
E. (A), (B), and (C) are all true.

Answer 1

During a CPET, a decrease in O₂ pulse and a drop in systolic blood pressure accompanied by symptoms of chest discomfort suggest reduced stroke volume and cardiac output, validating that both statements A and B are true.

Step-by-step explanation:

When performing a Cardiopulmonary Exercise Test (CPET) on a 57-year-old male with a history of myocardial infarction, several findings suggest compromised cardiovascular responses to exercise. A notable drop in the patient's O₂ pulse from 7ml/beat to 3ml/beat alongside a 30mmHg drop in systolic blood pressure and an increase in symptoms such as chest discomfort and shortness of breath led to the termination of the test. These observations are cause for concern due to their implications on the patient's cardiovascular health.

Statement A is true because the decrease in O₂ pulse can be an indicator of reduced stroke volume (SV), which might cause chest discomfort. Statement B is also true, as a reduction in SV would lead to a decreased cardiac output (CO), thereby causing the drop in systolic blood pressure, unless compensated by an increased heart rate (HR). While Statement C suggests a possible compensatory mechanism via the HR - VO2 (oxygen uptake) relationship, this was not observed in the given scenario.

Consequently, the correct answer is D. Both (A) and (B) are true as they accurately describe the direct consequences of the observations noted during the CPET.