Association between functional class and functional capacity measured by exercise stress test in patients with HFrEF

The New York Heart Association (NYHA) classification is widely used in clinical practice the clinical and prognostic assessment of patients with heart failure. However, it remains a subjective classification. On the other hand, the exercise stress test is an accessible complementary examination that allows a more objective evaluation of a patient's functional capacity. The aim of this study was to analyze the association between physician-perceived NYHA classification and exercise capacity measured by an exercise test.

This was an observational, analytical and retrospective study that included 300 patients with heart failure and left ventricular ejection fraction (LVEF) < 50% who underwent an exercise test between January 2018 and December 2022.

The majority of patients were classified as NYHA functional class I (59.3%). The association between NYHA classes and functional capacity was 0.280 (p < 0.001). NYHA class was associated with functional capacity, explaining 14.0% of the variation in METs (partial eta² = 0.140, p < 0.001). Adjusted mean METs were 7.77 (7.44–8.10) for NYHA I, 6.18 (5.76–6.59) for NYHA II, and 4.78 (3.52–6.04) for NYHA III. No association was found between NYHA classes and median N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels (p = 0.192) or heart rate recovery (p = 0.260).

NYHA classification was independently associated with exercise capacity. The association was modest, explaining only 14% of the variability. There was no significant association between NYHA classification and prognostic markers in heart failure, namely NT-proBNP and heart rate recovery.