A retrospective study on the impact of SARS-CoV-2 infection on cardiopulmonary function in a healthy Chinese cohort: a focus on “long COVID”

ObjectiveThis retrospective study aimed to observe the cardiopulmonary function and lingering symptoms in previously healthy individuals with Long COVID using Cardiopulmonary Exercise Testing (CPET), the gold standard for evaluating integrated human physiological function.MethodsA retrospective analysis was conducted on 73 subjects who completed CPET at Beijing Hospital of Traditional Chinese Medicine from January 2023 to April 2023. Participants were consecutively included and comprised 42 patients with confirmed SARS-CoV-2 infection and persistent symptoms (Long COVID group) and 31 healthy controls with no history of COVID-19 (Normal control group). The sample size was determined by the total number of eligible patients who consecutively underwent CPET during the study period, and a post-hoc power analysis confirmed sufficient power (>80%) to detect the observed differences in the primary endpoint (peakV̇O2%pred). General clinical data and CPET parameters were retrospectively collected and compared between the two groups. The chi-square test was used for sex distribution, the independent t-test IS for normally distributed continuous variables, and the Mann–Whitney U test for non-normally distributed variables. Linear regression analysis was performed to explore correlations between peak oxygen uptake (peakV̇O2) and other core CPET indicators.ResultsThere were 13 males and 18 females in the normal control group and12 males and 30 females in the Long COVID group. No statistical differences were observed in age, sex, height, or weight between the two groups (p > 0.05 for all). (2) In the Long COVID group, core CPET indicators were significantly reduced compared to the normal group: peakV̇O2 was78.3 ± 20.7% pred; anaerobic threshold (AT) was 77.9 ± 19.6% pred; peak oxygen pulse (peakO₂pulse) was 100.5 (82.4,110.3)% pred; and Oxygen Uptake Efficiency Plateau (OUEP) was 104.6 ± 12.9% pred (all p < 0.05). (3) Other indicators in the Long COVID group also showed significant differences compared to the normal group, including forced vital capacity (FVC) [3.2(2.8,3.8)L], resting heart rate (rest HR) (87.1 ± 9.3 bpm), peak tidal volume (peak VT) [1.4(1.2,1.9)L], Cardiac Power (CP) [3643.8(2868.7,4522.2)], and the slope of oxygen uptake to work rate (ρV̇O2/ρ WR) [9.6(9.0, 10.54)] (all p < 0.05). However, no significant differences were found in maximal voluntary ventilation (MVV) or peak heart rate (peak HR) between the two groups (p > 0.05). (4) In the Long COVID group, peak V̇O2 showed a significant positive linear correlation with AT (R2 = 0.63, p < 0.001), peakO₂pulse (R2 = 0.92, p < 0.001), and CP (R2 = 0.44, p < 0.001), but not with ρV̇O2/ρ WR (R2 = 0.04, p = 0.357). (5) Among the Long COVID group, the most frequently reported persistent symptoms were: decreased exercise endurance (19.1%), palpitations (16.1%), chest tightness and shortness of breath (12.6%), fatigue (16.9%), insomnia (7.8%), anxiety (7.3%), and cough (4.8%).ConclusionThis retrospective analysis confirms that SARS-CoV-2 infection has a significant and not merely short-term impact on the integrated cardiopulmonary and musculoskeletal function. Even after turning negative, individuals exhibit a wide range of symptoms affecting the respiratory, circulatory, and nervous systems. The observed reduction in peak systolic blood pressure, cardiac power, and the ρ V̇O2/ρ WR slope, coupled with compensatory resting tachycardia, suggests the possibility of multiple underlying mechanisms, including subclinical myocardial functional impairment, autonomic nervous system dysfunction, and/or peripheral deconditioning. CPET proved to be a safe and valuable tool for objectively evaluating the overall functional limitations in Long COVID patients.