This prospective study evaluates the impact of radiofrequency ablation (RFA) on cardiorespiratory indicators in patients with long-standing persistent atrial fibrillation admitted to the Heart Center UMC between January 2022 and April 2024 in Astana, Kazakhstan. The study aims to assess the functional cardiac benefits of RFA. Out of 717 registered atrial fibrillation patients, 104 were examined before and 3 months after ablation, focusing on cardiorespiratory parameters. A before-and-after analysis using linear mixed models was applied to evaluate changes in cardiorespiratory parameters post-RFA. Significant improvements were noted across various measures. VO₂ max increased from 11.5 ± 4.4 mL/kg/min to 18.0 ± 4.5 mL/kg/min (p < 0.001). Oxygen uptake improved from 7.2 ± 2.6 mL/beat to 11.0 ± 3.4 mL/beat (p < 0.001). The 6-min walking test distance rose from 306 ± 82 m to 400 ± 48 m (p < 0.001). METs increased from 4.4 ± 1.6 to 8.0 ± 1.3 (p < 0.001). Heart rate at peak exercise decreased from 175.5 ± 18.6 to 147.2 ± 12.3 beats per minute (p < 0.001). NT-proBNP levels decreased from 1357 ± 1182 to 415 ± 339 pg/mL (p < 0.001). Patients with persistent atrial fibrillation undergoing RFA showed functional improvements in CPET indicators such as VO₂ max, METs, O₂ pulse, heart rate, and the 6-min walking test. Improvements were also seen in Nt-proBNP analysis. These results emphasize the need for longitudinal follow-up to optimize outcomes and minimize medical risks.

Cardiorespiratory fitness (CRF) is a strong predictor of cardiovascular morbidity and mortality. This study aimed to describe age- and sex-specific reference values for CRF in healthy adults in Kazakhstan and to examine age-related changes in key physiological parameters, including peak heart rate and body mass index. The research included 3271 nonsmoking adults aged 20 to 59 years, free of health issues, who performed symptom-limited incremental cardiopulmonary exercise testing on a cycle ergometer between 2018 and 2025. The highest 30-s average value from exercise testing defined peak oxygen uptake (VO₂ peak). VO₂ peak were lower in older age groups in both sexes. In men, VO₂ peak values was 43.4 ± 7.41 mL/kg/min during ages 20-29 and 38.3 ± 6.32 mL/kg/min during ages 50-59. In women, corresponding VO₂ peak values were 39.2 ± 6.49 and 30.8 ± 5.78 mL/kg/min. Peak heart rate also was lower in older ages (men: 174 ± 11 to 142 ± 8 bpm; women: 179 ± 10 to 143 ± 11 bpm). Simple linear regression results showed that age was a significant predictor of VO₂ peak, BMI, and peak heart rate in both men and women (p < .001). This study provides the first nationally relevant descriptive data on CRF reference values for Kazakh adults.