Mark- Good comments as always. The point I was trying to make is that the role of CPX is infrequently included in cardiology guideline statements. Case in point, see the 2020 ACC/AHA Guideline for the Management of Patient with Valvular Heart Disease. click here for pdf CPX is mentioned once in this statement and oxygen consumption is mentioned twice.
Recommendations for clinical exercise testing in various populations can be found in chapter 5 on GETP10 if you wanted to switch up your population in your case study (if possible). this might help make it more applicable but still make your point that this testing can be more effective other than a last line resort
Mark- When you say CPX revealed the cardiac limitation, are you referring to the response in O2 pulse, a low anaerobic threshold, and/or other CPX measures? Or are you referring to quantifying the low exercise capacity with measured VO2? I ask this because I'd say a big part of the issue you are describing is due to a lack of empirical data supporting O2 pulse and anaerobic threshold as measures of cardiac dysfunction. As a result, CPX is not mentioned in guideline statements aimed at management of valve disease.