Beyond the slope: prognostic utility of the VE/VCO 2 intercept in chronic heart failure
Piergiuseppe Agostoni, Robin Willixhofer, Arianna Galotta, Filippo Maria Rubbo, Stefano Grosdani, Luca Felli, Raffaele Abete, Vincenzo Castiglione, Elisabetta Salvioni, Massimo Mapelli, Carlo Vignati, Beatrice Pezzuto, Irene Mattavelli, Carriere Cosimo, Nikita Baracchini, Teresa Maria Capovilla, Claudio Passino, Anna Apostolo, Pietro Palermo, Jeness Campodonico, Mauro C Contini, Lucia Tricarico, Emanuele Barbato, Emiliano Fiori, Michele Senni, Damiano Magrì, Annamaria Iorio, Susanna Sciomer, Michele Correale, Gaia Cattadori, Michele Emdin, Gianfranco SinagraAims
Cardiopulmonary exercise testing (CPET) parameters are used for heart failure (HF) prognostication. While the ventilation to carbon dioxide production (VE/VCO 2 ) slope ≥34 identifies high risk, patients with intermediate values remain heterogeneous. The VE/VCO 2 Y-intercept, reflecting dead space ventilation at rest and its changes during effort, may refine prognostication.
Methods
We retrospectively analysed 2642 HF. Follow-up was 26 (9–63) months. The study endpoint was the composite of all-cause death, urgent transplant or left ventricular assist device implantation.
Results
Median age was 62 (53–70) years and left ventricular ejection fraction (LVEF) 33% (27%–39%). 27% of patients were New York Heart Association class III–IV. During follow-up, 534 events occurred. Both VE/VCO ₂ slope and peakVO ₂ were associated with outcome in univariable and multivariable models (HR 1.04, 95% CI 1.03 to 1.06; HR 0.90, 95% CI 0.88 to 0.93, p<0.001, respectively). Y-intercept was not prognostic univariately but added independent value in multivariable models (HR 1.08, 95% CI 1.04 to 1.13, p<0.001). Prognosis and clinical profiles improved from group A (VE/VCO 2 slope ≥34, n=858) to B (28–34, n=943) to C (<28, n=841). Group A versus C patients had lower LVEF (30% (25%–36%) vs 35% (30%–40%), p trend <0.001), peakVO ₂ (12.7 (10.06–15.3) vs 17.7 (14.6–21.6) mL/kg/min, p trend <0.001) and higher N-terminal pro-B-type natriuretic peptide (1400 (572–3122) vs 454 (174–1081) pg/mL, p trend <0.001). Only within group B, a high median Y-intercept (B1≥3.9 L/m) clearly identified patients with higher HF severity and worse survival than B2 (<3.9 L/m, log-rank p<0.001).
Conclusion
An increase in the VE/VCO 2 slope is associated with a progressive lower survival. Y-intercept enhances risk assessment in HF with intermediate VE/VCO ₂ slope values.