Korean J Intern Med.  2023 Jul;38(4):514-525. 10.3904/kjim.2022.375.

Development and validation of equation for cardiorespiratory fitness in patients with heart failure with preserved ejection fraction

• Battumur B
• Lee JE
• Park SH
• Choi YJ
• Kang DO
• Park EJ
• Kim JB
• Choi JY
• Roh SY
• Na JO
• Choi CU
• Kim JW
• Rha SW
• Park CG
• Kim EJ

• KMID: 2544195
• DOI: http://doi.org/10.3904/kjim.2022.375

Abstract

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 (p < 0.001) and underestimated by the FRIEND-HF equation (p <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, p = 0.124), whereas the VO₂max estimated by the other three equations was still significantly different from the directly measured VO₂max in group B (all p < 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.

Keyword

Heart failure; Cardiorespiratory fitness; Oxygen consumption; Validation study; Metabolic equivalent