Normalization for peak oxygen uptake increases the prognostic power of the ventilatory response to exercise in patients with chronic heart failure

Marco Guazzi, Stefano De Vita, Paola Cardano, Simona Barlera, Maurizio D. Guazzi

Research output: Contribution to journalArticle

Abstract

Background: Peak exercise oxygen uptake (peak VO 2) and ventilation to CO 2 production (VE/VCO 2) slope are established prognostic indicators in patients with chronic heart failure (CHF). A high VE/VCO 2 slope, however, does not take into account the level of physical performance as expressed by peak VO 2. We hypothesized that the prognostic value of a high VE/VCO 2 slope may be improved by normalization for peak VO 2 (VE/VCO 2/VO 2). Methods: One hundred patients with CHF underwent pulmonary function tests at rest (spirometry and lung diffusion capacity) and maximal cardiopulmonary exercise testing. The prognostic value of VE/VCO 2 slope, peak VO 2 and VE/VCO 2/VO 2 was probed prospectively. Results: Twenty-one patients died from cardiac reasons during a mean follow-up of 26 ± 19 months. Nonsurvivors, compared to survivors, showed a lower peak VO 2 (13.6 ± 4.0 vs 17.5 ± 4.1 mL · min -1 · kg -1, P <.01) and a steeper VE/VCO 2 slope (43 ± 11 vs 31.6 ± 5.0, P <.01). Nonetheless, in patients whose VE/VCO 2 slope exceeded 34 (upper normal limit), there was no correlation with peak VO 2 (r = -35, P = not significant). Interestingly 35% of them showed a normal exercise performance (peak VO 2 ≥18 mL · min -1 · kg -1). At multivariate analysis, the VE/VCO 2 slope showed a prognostic power stronger than that of peak VO 2; however, the VE/VCO 2/VO 2 index retained a prognostic power greater than that of both VE/VCO 2 slope and peak VO 2. A VE/VCO 2/VO 2 ≥2.4 signaled cases at higher risk. Conclusions: Discrepancies between VE/VCO 2 slope and peak VO 2 may generate uncertainty. Normalization of the former by the latter improves outcome prediction and may be considered a simple and effective way for maximizing the clinical applicability of these 2 indicators.

Original languageEnglish
Pages (from-to)542-548
Number of pages7
JournalAmerican Heart Journal
Volume146
Issue number3
DOIs
Publication statusPublished - Sep 1 2003

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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