Discordance between reported functional limitation and objective exercise capacity assessed by cardiopulmonary exercise testing in heart failure

Background

Functional status in heart failure is traditionally determined using symptom-based classifications such as the New York Heart Association (NYHA) class, although their relationship with objectively measured exercise capacity remains uncertain.

Purpose

To evaluate the agreement between symptom status and objective exercise limitation assessed by cardiopulmonary exercise testing (CPET) and to identify clinical characteristics associated with physiological impairment.

Methods

A single-centre observational study included consecutive patients with heart failure referred for clinically indicated CPET. Functional limitation was assessed using NYHA class. Objective exercise limitation was defined as peak oxygen consumption (VO2 peak) <80% of predicted values.

Continuous variables were compared using the Mann–Whitney U test and categorical variables using Fisher’s exact test. The relationship between symptom severity and objective limitation was further explored using ordinal trend analysis across NYHA classes. Sensitivity analysis evaluated higher symptom burden (NYHA ≥III vs NYHA I–II). Associations with heart failure–related hospitalisation were explored as clinical validation.

Results

Eighty-one patients were included, of whom 61 (75.3%) were symptomatic (NYHA ≥II). Objective exercise limitation was identified in 70 patients (86.4%).

Symptomatic patients were more likely to demonstrate objective limitation compared with asymptomatic individuals; however, this association did not reach statistical significance (odds ratio 3.06, 95% confidence interval 0.82–11.40; Fisher exact p=0.128). Symptom–physiology discordance was observed in 6 patients, corresponding to 9.8% of symptomatic individuals who demonstrated preserved objective exercise capacity despite reported limitation.

Although higher NYHA class showed a non-significant trend towards greater likelihood of objective limitation (trend p=0.134), increasing symptom severity did not meaningfully improve discrimination. Consistently, sensitivity analysis using NYHA ≥III demonstrated no significant association with physiological impairment (odds ratio 1.93, 95% confidence interval 0.38–9.70; Fisher exact p=0.720), with persistent discordance among NYHA ≥III patients (2/23, 8.7%).

Objective exercise limitation showed closer association with heart failure–related hospitalisation compared with symptom classification alone.

Conclusion

In this real-world heart failure cohort, symptom-based functional classification showed limited agreement with objectively measured exercise capacity. Increasing symptom severity did not improve identification of physiological impairment, while objective exercise testing demonstrated stronger clinical relevance. These findings support broader use of CPET for accurate functional assessment and risk stratification in heart failure.DistributionpeakVO2