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(Circulation. 2000;102:e182.)
© 2000 American Heart Association, Inc.

Correspondence

Ventilatory and Heart Rate Responses to Exercise: Better Predictors of Heart Failure Mortality Than Peak Exercise Oxygen Consumption

Guy A. MacGowan, MD, FACC; Srinivas Murali, MD, FACC

Section of Heart Failure and Transplantation Cardiology, Cardiovascular Institute of the University of Pittsburgh Medical Center, 200 Lothrop Street, Pittsburgh, PA 15213

To the Editor:

We read with great interest the article by Robbins et al¹ describing how exercise-related ventilatory and heart rate responses better predict heart failure mortality than peak exercise oxygen consumption.²

Although Robbins et al¹ correctly state that other investigators have shown that exercise-related ventilatory abnormalities can be useful in predicting mortality,³ they fail to acknowledge the fact that our group⁴ previously published similar findings, which demonstrated that ventilatory abnormalities were related to outcome in congestive heart failure. Importantly, we demonstrated that by combining ventilatory abnormalities and peak exercise oxygen consumption, patients at a particularly high risk for death could be identified. These findings are similar to the data presented in Figures 1, 5, and 7 of the article by Robbins et al.¹ In patients with minute ventilation/carbon dioxide production (E/CO₂) >50 and a peak exercise oxygen consumption <15 mL · kg^-1· min^-1, we described a mortality rate of 82% (median follow-up time, 552±329 days) compared with a mortality of 22% in patients with a E/CO₂ <50 and a peak exercise oxygen consumption <15 mL · kg^-1 · min^-1. In addition, Robbins et al¹ state that the value of E/CO₂ at the anaerobic threshold was almost as strong a predictor of mortality as E/CO₂ at peak exercise. We also used E/CO₂ at the anaerobic threshold⁴ because it predicted outcome better than E/CO₂ at peak exercise. Robbins et al¹ further state that there was a threshold phenomenon regarding E/CO₂ values, with mortality increasing markedly as values exceeded 40 to 45. Similarly, our data clearly show a marked increase in mortality with values >50. The study by Robbins et al² had a follow-up period similar to ours; however, they deserve credit for studying a larger patient population and for analyzing data regarding chronotropic responses to exercise.

On the basis of these published data,⁴ we have used exercise-related ventilatory responses in conjunction with peak exercise oxygen consumption to evaluate candidates for transplantation for the past 3 years at the University of Pittsburgh Medical Center. We believe that a proper scientific evaluation of the hypothesis that exercise-related ventilatory responses provide additional prognostic information in heart failure beyond that provided by peak exercise oxygen consumption requires a full recognition of all pertinent, previously published studies. Clearly, this is an important area of clinical research that may have a substantial impact on the management of patients with congestive heart failure.

References

1. Robbins M, Francis G, Pashkow FJ, et al. Ventilatory and heart rate responses to exercise: better predictors of heart failure mortality than peak oxygen consumption. Circulation. 1999;100:2411–2417.[Abstract/Free Full Text]
   
2. Mancini DM, Eisen H, Kussmaul W, et al. Value of peak exercise oxygen consumption for optimal timing of cardiac transplantation in ambulatory patients with heart failure. Circulation. 1991;83:778–786.>[Abstract/Free Full Text]
   
3. Chua TP, Ponikowksi P, Harrington D, et al. Clinical correlates and prognostic significance of the ventilatory response to exercise in chronic heart failure. J Am Coll Cardiol. 1997;29:1585–1590.[Abstract]
   
4. MacGowan GA, Janosko K, Cecchetti A, et al. Exercise-related ventilatory abnormalities and survival in congestive heart failure
   

Response

Michael S. Lauer, MD; Mark Robbins, MD; Fredric Pashkow, MD; Kathy Hoercher, RN; Claire E. Snader, MA; James B. Young, MD; Gary Francis, MD

Department of Cardiology, Cleveland Clinic Foundation, Cleveland, Ohio, lauerm@cesmtp.ccf.org

We thank Drs MacGowan and Murali for their letter. We agree that their study,^R1 along with ours and those of others,^R2 strongly support the view that ventilatory responses to exercise must be carefully considered when risk-stratifying patients with severe heart failure. We are also now routinely incorporating the ventilatory response to exercise in our metabolic stress test reports and in our considerations regarding candidacy for cardiac transplantation.

References

1. MacGowan GA, Janosko K, Cecchetti A, et al. Exercise-related ventilatory abnormalities and survival in congestive heart failure. Am J Cardiol. 1997;79:1264–1266.[Medline] [Order article via Infotrieve]
   
2. Chua TP, Ponikowski P, Harrington D, et al. Clinical correlates and prognostic significance of the ventilatory response to exercise in chronic heart failure. J Am Coll Cardiol. 1997;29:1585–1590.
   

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