The American Heart Association (AHA) guidelines assess heart failure (HF) via comorbidities, laboratory markers, and echocardiography, while the New York Heart Association (NYHA) classification evaluates functional capacity. The primary objective of this study was to investigate the correlation between objectified HF-related symptoms and cardiac and muscular exercise capacity in Stage B HF patients with non-reduced ejection fraction. As secondary endpoints, we stratified this analysis for subgroups of NYHA classes to evaluate the primary endpoint for different levels of impairment and for sex to address for differences between men and women. Sixty-two Stage B HF patients with non-reduced EF were screened from an HF-risk cohort. Assessments included medical history, HF-related symptoms (Kansas City Cardiomyopathy Questionnaire, KCCQ), physical examination, laboratory tests, echocardiography, and cardiopulmonary exercise testing (CPET) with cardiac output monitoring. Correlations were analyzed between KCCQ score and exercise capacity markers: maximal oxygen uptake (VO