CORRESPONDENCE: LETTERS TO THE EDITOR
Reply
Pascal de Groote, MD,
Joël Dagorn, MD,
Benoit Soudan, MD,
Nicolas Lamblin, MD,
Eugene Mc Fadden, FRCPI, FACC and
Christophe Bauters, MD, FACC
Hopital Cardiologique, Service de Cardiologie C, CHRU de Lille, Bd Prof J Leclercq, 59037 Lille Cedex, France
(Email: pdegroote{at}chru-lille.fr).
The letter by Dr. Bard raises the important aspect of the standardization of the cardiopulmonary exercise test (CPT). We agree that peak respiratory exchange ratio (RER) is a mandatory parameter for the interpretation of CPT. Peak RER is a good index of a maximal effort, and prognostic value of peak VO2 is dependent on peak RER (1). As in our previous studies (2,3), peak RER in the present study (4) was elevated (1.17 ± 0.14), with a significant difference between survivors and nonsurvivors (1.18 ± 0.14 vs. 1.14 ± 0.13; p = 0.03). However, peak RER was not an independent predictor of cardiac survival.
We also agree that the analysis of the ventilatory efficiency of the patients, determined either by the peak VE/VCO2 or by the VE/VCO2 slope, could bring important prognostic information (5–7). As suggested by Dr. Bard, it is important to standardize the analysis of the results of the CPT. However, the major problem with the VE/VCO2 slope is the nonstandardization of its determination. In some patients, the relationship between VE and VCO2 is not linear, and two slopes could be determined, the second one steeper that the first one. Several methods have been used for the determination of the VE/VCO2 slope (using all the data of the exercise or only data obtained before or after the ventilatory threshold). Preliminary results suggest that the best method is to use all the data from the exercise (8,9). Because the determination of the VE/VCO2 slope is not yet standardized, it is difficult to include it in prognostic studies. However, when peak VE/VCO2 was included in our multivariate analysis, it was not an independent predictor of cardiac survival. Currently, peak VO2 remains the most powerful prognostic parameter of the CPT in our population.
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7. Francis DP, Shamim W, Davies LC, et al. Cardiopulmonary exercise testing for prognosis in chronic heart failure: continuous and independent prognostic value from VE/VCO2 slope and peak VO2 Eur Heart J 2000;21:154-161.[Abstract/Free Full Text]
8. Arena R, Myers J, Aslam SS, Varughese EB, Peberdy MA. Technical considerations related to the minute ventilation/carbon dioxide output slope in patients with heart failure Chest 2003;124:720-727.[Abstract/Free Full Text]
9. Tabet JY, Beauvais F, Thabut G, et al. A critical appraisal of the prognostic value of the VE/VCO2 slope in chronic heart failure Eur J Cardiovasc Prev Rehabil 2003;10:267-272.[CrossRef][Web of Science][Medline]
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