Elsevier

American Heart Journal

Volume 156, Issue 6, December 2008, Pages 1177-1183
American Heart Journal

Clinical Investigation
Congestive Heart Failure
A cardiopulmonary exercise testing score for predicting outcomes in patients with heart failure

https://doi.org/10.1016/j.ahj.2008.07.010Get rights and content

Objective

The aim of this study is to evaluate the predictive accuracy of a cardiopulmonary exercise test (CPX) score.

Background

Cardiopulmonary exercise test responses, including peak VO2, markers of ventilatory inefficiency (eg, the VE/VCO2 slope and oxygen uptake efficiency slope [OUES]), and hemodynamic responses, such as heart rate recovery (HRR) and chronotropic incompetence (CRI) are strong predictors of outcomes in patients with heart failure (HF). However, there is a need for simplified approaches that integrate the additive prognostic information from CPX.

Methods

At 4 institutions, 710 patients with HF (568 male/142 female, mean age 56 ± 13 years, resting left ventricular ejection fraction 33 ± 14%) underwent CPX and were followed for cardiac-related mortality and separately for major cardiac events (death, hospitalization for HF, transplantation, left ventricular assist device implantation) for a mean of 29 ± 25 months. The age-adjusted prognostic power of peak VO2, VE/VCO2 slope, OUES (VO2 = a log10VE + b), resting end-tidal carbon dioxide pressure (PetCO2), HRR, and CRI were determined using Cox proportional hazards analysis, optimal cutpoints were determined, the variables were weighted, and a multivariate score was derived.

Results

There were 175 composite outcomes. The VE/VCO2 slope (≥34) was the strongest predictor of risk and was attributed a relative weight of 7, with weighted scores for abnormal HRR (≤6 beats at 1 minute), OUES (>1.4), PetCO2 (<33 mm Hg), and peak VO2 (≤14 mL kg−1 min−1) having scores of 5, 3, 3, and 2, respectively. Chronotropic incompetence was not a significant predictor and was excluded from the score. A summed score >15 was associated with an annual mortality rate of 27% and a relative risk of 7.6, whereas a score <5 was associated with a mortality rate of 0.4%. The composite score was the most accurate predictor of cardiovascular events among all CPX responses considered (concordance indexes 0.77 for mortality and 0.75 for composite outcome composed of mortality, transplantation, left ventricular assist device implantation, and HF-related hospitalization). The summed score remained significantly associated with increased risk after adjusting for age, gender, body mass index, ejection fraction, and cardiomyopathy type.

Conclusion

A multivariable score based on readily available CPX responses provides a simple and integrated method that powerfully predicts outcomes in patients with HF.

Section snippets

Methods

This study was a multicenter analysis including patients with HF from the exercise laboratories at the VA Palo Alto Health Care System and Stanford University, Palo Alto, CA; San Paolo Hospital, Milan, Italy; Virginia Commonwealth University, Richmond, VA; and the LeBauer Cardiovascular Research Foundation, Greensboro, NC. A total of 710 patients with chronic HF (568 males and 142 females), tested between March 18, 1993 and March 5, 2007, were included. Inclusion criteria consisted of a

Baseline characteristics and development of the summed score

The study sample is composed of 568 males and 142 females with CHF; 331 (49%) had an ischemic etiology. The BMI and ejection fraction were higher among those who survived versus those who died (Table I). Among CPX variables, peak VO2 (17.5 ± 6.6 vs 14.0 ± 4.7 mL kg−1 min−1), peak heart rate, HRR, OUES, and PetCO2 were higher among those who survived. Conversely, the VE/VCO2 slope and the CPX weighted summed score were lower among survivors (P < .001 for both) (Table II).

There were 175 total

Discussion

Beginning in the mid-1990s, consensus guidelines recommended the application of the CPX to supplement other clinical data in the management of patients with HF. However, these guidelines limited their recommendations to the application of peak VO2 achieved in the context of selecting patients for transplantation. In recent years, a broader appreciation of the CPX has occurred, and an expanding number of responses from the test have been applied to predict risk in patients with HF. This has led

Summary

This study further defines the important role of the CPX for predicting outcomes in patients with HF. Rather than relying strictly on peak VO2, the simple summation of several easily obtained responses from the CPX can be used to more accurately describe the spectrum of risk for adverse events in these patients. By including indices that reflect abnormalities in several systems that are related to outcomes, including oxygen delivery and extraction (peak VO2), ventilatory inefficiency (VE/VCO2

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