Background/Aims: Cardiorespiratory fitness (CRF), as measured by maximal oxygen consumption (VO2max), is an important independent predictive factor of cardiovascular outcomes in patients with heart failure (HF). However, it is unclear whether conventional equations for estimating CRF are applicable to patients with HF with preserved ejection fraction (HFpEF).Methods: This study included 521 patients with HFpEF (EF ≥ 50%) whose CRF was directly measured by cardiopulmonary exercise test using a treadmill. We developed a new equation (Kor-HFpEF) for half of the patients in the HFpEF cohort (group A, n = 253) and validated it for the remaining half (group B, n = 268). The accuracy of the Kor-HFpEF equation was compared to that of the other equations in the validation group.Results: In the total HFpEF cohort, the directly measured VO₂max was significantly overestimated by the FRIEND and ACSM equations (<i>p</i> < 0.001) and underestimated by the FRIEND-HF equation (<i>p</i> <0.001) (direct 21.2 ± 5.9 mL/kg/min; FRIEND 29.1 ± 11.8 mL/kg/min; ACSM 32.5 ± 13.4 mL/kg/min; FRIEND-HF 14.1 ± 4.9 mL/kg/min). However, the VO₂max estimated by the Kor-HFpEF equation (21.3 ± 4.6 mL/kg/min) was similar to the directly measured VO₂max (21.7 ± 5.9 mL/kg/min, <i>p</i> = 0.124), whereas the VO₂max estimated by the other three equations was still significantly different from the directly measured VO₂max in group B (all <i>p</i> < 0.001).Conclusions: Traditional equations used to estimate VO₂max were not applicable to patients with HFpEF. We developed and validated a new Kor-HFpEF equation for these patients, which had a high accuracy.

Background Exercise capacity is known to be an independent predictor of cardiovascular events and mortality. However, most previous studies were based on Western populations. Further study is warranted for Asian patients according to ethnic or national standards. We aimed to compare prognostic values of Korean and Western nomograms for exercise capacity in Korean patients with cardiovascular disease (CVD). Methods In this retrospective cohort study, we enrolled 1,178 patients (62 ± 11 years; 78% male) between June 2015 and May 2020, who were referred for cardiopulmonary exercise testing in our cardiac rehabilitation program. The median follow-up period was 1.6 years. Exercise capacity was measured in metabolic equivalents by direct gas exchange method during the treadmill test. The nomogram for exercise capacity from healthy Korean individuals and a previous landmark Western study was used to determine the percentage of predicted exercise capacity. The primary endpoint was the composite of major adverse cardiovascular events (MACE; all-cause death, myocardial infarction, repeat revascularization, stroke and hospitalization for heart failure). Results A multivariate analysis showed that the risk of primary endpoint was more than double (hazard ratio [HR], 2.20; 95% confidence interval [CI], 1.10–4.40) in the patients with lower exercise capacity (< 85% of predicted) by Korean nomogram. The lower exercise capacity was one of the strong independent predictors along with left ventricular ejection fraction, age, and level of hemoglobin. However, the lower exercise capacity by Western nomogram could not predict the primary endpoint (HR, 1.33; 95% CI, 0.85–2.10). Conclusion Korean patients with CVD with lower exercise capacity have higher risk of MACE. Considering inter-ethnic differences in cardiorespiratory fitness, the Korean nomogram provides more suitable reference values than the Western nomogram to determine lower exercise capacity and predict cardiovascular events in Korean patients with CVD.

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