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Communications to the Editor |

Exercise Limitation Testing Exercise Limitation Testing FREE TO VIEW

John F. Whitney, MD
Author and Funding Information

Affiliations: Albany Medical College, Albany, NY. Dr. Whitney is Assistant Professor of Medicine at Albany Medical College.,  Associate Professor of Medicine, University of British Columbia, Vancouver, British Columbia, Canada

Correspondence to: John F. Whitney, MD, FCCP, Assistant Professor of Medicine, Albany Medical College, Mail Code A-91, 47 New Scotland Ave, Albany, NY 12208



Chest. 1999;116(4):1141-1142. doi:10.1378/chest.116.4.1141
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To the Editor:

Peak oxygen consumption analysis has become standard practice for the presurgical evaluation of a variety of patient groups. This has lead to a marked increase in the availability of the testing apparatus in smaller institutions and a proportional increase in the number of persons undergoing the tests. Performing a cardiopulmonary exercise test (CPET) is easily accomplished in these settings, however, data analysis is often limited to whatever the computer software that is sold with the system provides.

The article by Ramos-Barbon et al (February 1999)1 seems to limit the analysis of exercise limitation to simply a cardiovascular or a ventilatory endpoint. In their analysis, if a specific heart rate (HR) or ventilatory limitation does not exist, the patient must have given submaximal effort or have deconditioning as the cause. In fact, many other endpoints exist that are readily obtained without overly invasive testing (ie, an a-line or a Swan-Ganz catheter are not needed). Many heart failure patients have poorly detectable anaerobic thresholds (AT) when noninvasive means are used to detect. Traditionally, the solution would be to place an a-line and repeat the test. In my experience, obtaining an arterial blood gas (ABG) with a lactate level at the end of exercise will provide you with an abundance of information to show whether the patient in question was giving full effort and whether the AT was crossed. In many patients without apparent HR or ventilatory limitation, the ABG will show compensated metabolic acidosis with significant arterial lactate concentrations, which suggests that the effort was full. It still leaves the question of deconditioning vs cardiac limitation technically unanswered but would suggest that the patient is cardiac limited.

Many other forms of exercise limitations exist, and some of these may be relevant in the population of patients with heart failure. In particular, gas exchange abnormalities (increased ventilatory equivalent for CO2) may develop without necessarily showing desaturation of the pulse oximetry. This may result in dyspnea, which limits exercise though it is not truly a “cardiac limitation.”

In summary, I find the analysis and conclusion lacking because of a failure to investigate for other forms of exercise limitation beyond the usually obviously HR or ventilatory criteria. It would be interesting to obtain end-exercise ABGs for these patients and then enroll them in exercise programs to see how much of the limitation can be reversed with exercise training.

Ramos-Barbon, D, Fitchett, D, Gibbons, W, et al (1999) Maximal exercise testing for the selection of heart transplantation candidates: limitation of peak oxygen consumption.Chest115,410-417. [PubMed] [CrossRef]
 

Exercise Limitation Testing

To the Editor:

We wish to thank Dr. Whitney for his interest in our article (February 1999).1 We agree entirely that the causes of exercise limitation in patients with congestive heart failure are complex and numerous. However, the intent of our study was not to determine the causes of exercise limitation in our subjects. Rather, we wished to demonstrate that peak oxygen consumption (V̇o2) is not necessarily synonymous with maximum achievable V̇o2.

Many heart failure patients are unaccustomed to “pushing” themselves during exercise, either as a result of unpleasant symptoms (eg, breathlessness or leg discomfort) or of fear of medical consequences. A cardiopulmonary exercise test (CPET) performed for clinical reasons outside of the context of a research protocol, even when conducted in a high-quality physiology laboratory by experienced personnel, may yield an erroneous interpretation unless there is objective evidence on the study indicating that the subject performed a maximum effort.

In our study, a sizable proportion of heart failure patients referred for CPET did not have objective evidence for an exercise limitation on the test. They may well have reached a physiologic maximum, however, we were unable to confirm that on routine testing. Consequently, as we pointed out in our conclusion, the use of peak V̇o2 for determining candidacy for heart transplantation should be carefully evaluated for evidence that maximal exercise has been achieved to avoid biasing the selection of heart transplant candidates.

References
Ramos-Barbon, D, Fitchett, D, Latter, D, et al Maximal exercise testing for the selection of heart transplantation candidates: Limitation of peak oxygen consumption.Chest1999;115,410-417. [PubMed] [CrossRef]
 

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References

Ramos-Barbon, D, Fitchett, D, Gibbons, W, et al (1999) Maximal exercise testing for the selection of heart transplantation candidates: limitation of peak oxygen consumption.Chest115,410-417. [PubMed] [CrossRef]
 
Ramos-Barbon, D, Fitchett, D, Latter, D, et al Maximal exercise testing for the selection of heart transplantation candidates: Limitation of peak oxygen consumption.Chest1999;115,410-417. [PubMed] [CrossRef]
 
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