The relationship between homocysteine and cardiopulmonary exercise testing in patients with acute coronary syndrome after percutaneous coronary intervention
Authors: Luo Jun-Ting , Zeng Chun-Mei , Zhao Yan-Mei , Zeng Zhi-Yu 
Published: January 2023

Abstract
Objective
The purpose of this study was to investigate the relationship between homocysteine (Hcy) levels and cardiopulmonary exercise testing (CPET) in patients with acute coronary syndrome (ACS) after percutaneous coronary intervention (PCI). We also explored the relationship between Hcy levels and cardiac ultrasonography.

Methods
This study comprised 261 patients with ACS who underwent coronary angiography and PCI at Yulin First Hospital from January 2020 to June 2021. All subjects completed basic data collection, laboratory examination, CPET and cardiac ultrasonography. The CPET includes the peak oxygen uptake (peak VO2), anaerobic threshold (AT), metabolic equivalents (METs), exercise load (load), oxygen pulse (O2 pulse), end-tidal CO2 partial pressure (PETCO2), ventilatory equivalents for carbon dioxide (VE/VCO2) and Oxygen uptake efficiency (OUES). Cardiac ultrasonography was used to evaluate the left ventricular end diastolic diameter (LVEDD), interventricular septal thickness (IVST), left ventricular posterior wall thickness (LVPWT) and left ventricular ejection fraction (LVEF). A serum Hcy level ≥ 15 µmol/L was defined as hyperhomocysteinemia (HHcy). The patients were divided into the Hcy < 15 µmol/L group (n = 189) and the Hcy ≥ 15 µmol/L group (n = 72).

Results
The average age of the participating patients was 58.9 ± 10.1 years. The majority of participants were male (86.6%). The CPET indices of METs, load, VO2/kg, and PETCO2 were significantly decreased in the Hcy ≥ 15 µmol/L group compared with the Hcy < 15 µmol/L group. Additionally, the CPET index of the VE/VCO2 slope and the cardiac ultrasonography indices of IVST and LVPWT were significantly increased in the Hcy ≥ 15 µmol/L group compared with the Hcy < 15 µmol/L group. These differences were statistically significant (P < 0.05). Correlation analysis showed that Hcy levels were negatively correlated with METs, VO2/kg and PETCO2 and positively correlated with the VE/VCO2 slope (P < 0.05). Partial correlation analysis showed that Hcy levels were negatively correlated with METs and VO2/kg in the AT state. The correlation coefficients were − 0.172 and − 0.172, respectively (P < 0.05). Hcy levels were negatively correlated with METs, VO2/kg and PETCO2 in the peak state. The correlation coefficients were − 0.177, -0.153 and − 0.129, respectively (P < 0.05). After further adjustment for confounders, multiple linear regression analysis showed that Hcy levels were negatively correlated with METs and VO2/kg in the AT state and peak state. The standardized regression coefficients were − 0.035, -0.122, -0.048 and − 0.128, respectively (P < 0.05). Correlation analysis showed that Hcy levels were positively correlated with the IVST and LVPWT (P < 0.05), but after adjusting for confounding factors, partial correlation analysis showed that there was no correlation between them.

Conclusion
A high Hcy level is associated with lower METs and VO2/kg and worse cardiopulmonary function in patients with ACS after PCI.