Congestive Heart Failure
Ventilatory response to exercise improves risk stratification in patients with chronic heart failure and intermediate functional capacity*

https://doi.org/10.1067/mhj.2002.120772Get rights and content

Abstract

Background Peak oxygen consumption (VO2) has an important prognostic role in chronic heart failure (CHF), but its discriminatory power is limited in patients with intermediate exercise capacity (peak VO2 between 10-18 mL/kg/min). Thus, supplementary exertional indexes are greatly needed. Methods Six hundred patients with CHF with left ventricular ejection fraction (LVEF) ≤40% who performed a symptom-limited cardiopulmonary exercise testing were screened and followed up for 780 ± 450 days. Results Eighty-seven patients had major cardiac events (77 cardiac deaths and 10 urgent heart transplantations). Multivariate analysis revealed the rate of increase of minute ventilation per unit of increase of carbon dioxide production (VE/VCO2 slope) (χ2, 79.3, P <.0001), LVEF (χ2, 24.6, P <.0001), and peak VO22, 9.4, P <.0001) as independent and additional predictors of major cardiac events. VE/VCO2 slope was the strongest independent predictor of outcome (χ2, 20.9, P =.0001) in patients with intermediate peak VO2 (n = 403), and the best cutoff value was 35 (χ2, 25.8; relative risk = 3.2, 95% CI 2.0-5.1, P <.0001). Total mortality rate was 30% in patients with VE/VCO2 slope ≥35 (n = 103, 26%) and 10% in those with VE/VCO2 slope <35 (n = 300, 74%) (P <.0001). Patients with VE/VCO2 slope ≥35 had a similar total mortality rate to those with peak VO2 ≤10 mL/kg/min (30% vs 37%, P not significant). Conclusions A rational and pragmatic risk stratification process with symptom-limited cardiopulmonary exercise testing in CHF should include both peak VO2 and VE/VCO2 slope, the latter index effectively predicting outcome in almost one fourth of patients with intermediate exercise capacity. (Am Heart J 2002;143:418-26.)

Section snippets

Study population

The study cohort consisted of 600 patients with CHF caused by ischemic or idiopathic dilated cardiomyopathy referred for CPX as part of functional evaluation, between July 1995 and March 2000. All patients had a history of an unequivocal clinical episode of heart failure and were on stable medical treatment for at least 1 month at the time of the study. Eligibility criteria were (1) echocardiographic left ventricular ejection fraction (LVEF) ≤40%, (2) ability to perform a CPX until exhaustion

Results

The study population included 530 men and 70 women: mean age was 58 ± 7 years. The etiology of heart failure was idiopathic dilated cardiomyopathy in 180 patients (30%) and coronary artery disease in 420 (70%). Despite optimal medical treatment, the majority of patients were in New York Heart Association (NYHA) functional class II-III (n = 475), whereas fewer than one fourth (n = 125) did not complain of symptomatic limitation at the time of CPX. Mean peak VO2, VE/VCO2 slope, and

Study findings

Our data indicate that an abnormally high VE/VCO2 slope, a low LVEF, and a low peak VO2 are powerful and independent predictors of major cardiac events in patients with CHF. Although a peak VO2 value of 13 mL/kg/min significantly discriminates survivors from nonsurvivors in our population, we confirm that functional capacity is strongly correlated with mortality among patients achieving a peak VO2 ≤10 mL/kg/min and distinctly predicts a very good prognosis in those with a peak VO2 ≥18

Acknowledgements

We thank Alfio Agazzone, Elena Bonanomi, and Barbara Temporelli for technical support; Fabio Comazzi for statistical analysis; and Rosemary Allpress for her careful revision of the English manuscript.

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*

Reprint requests: Ugo Corrà, MD, Divisione di Cardiologia, Fondazione “S. Maugeri,” Via per Revislate, 13, 28010 Veruno (NO), Italy.E-mail: [email protected]

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