Author(s): BALDASSARRE, G., ZUCCARELLI, L., FAVARETTO, T., URSELLA, C., PALOMBA, A., SOZIO, E., TASCINI, C., GRASSI, B., Institution: UNIVERSITÀ DEGLI STUDI DI UDINE, Country: ITALY, Abstract-ID: 1087

INTRODUCTION:
Following the acute infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a substantial percentage of patients refer persisting and often debilitating symptoms like dyspnea, fatigue and exercise intolerance. These symptoms are often grouped in a syndrome termed “Long COVID”. The aim of the present study was to evaluate the persistence of Long COVID symptoms after about 2 years from the original infection, and to investigate potential pathophysiological mechanisms.
METHODS:
After about two years (26±5 months, x±SD) from the original COVID-19 infection, 26 sedentary patients, males and females, were recruited for the present study. Among these patients, 12 (Long COVID; 57±6 yr) complained the persistence of symptoms related to Long COVID, whereas 14 (CTRL; 57±8 yr) did not refer these symptoms. Quality of life was assessed by the SF-36 questionnaire. Microvascular/endothelial function (increased femoral artery blood flow) during passive leg movements was evaluated by Eco-Doppler. Knee extensors maximal muscle force was assessed by isometric dynamometry. Participants performed an incremental test (INCR) and a moderate-intensity (MOD) exercise on a cycle ergometer. Pulmonary gas exchange was determined. Skeletal muscle oxidative function was evaluated in-vivo by determining the recovery kinetics of skeletal muscle O2 uptake (V̇O2m) by near-infrared spectroscopy and the repeated occlusions method.
RESULTS:
Significantly lower scores were observed in Long COVID vs. CTRL patients in all the investigated domains by SF-36, indicating a poorer quality of life in the first group. No signs of sarcopenia were identified by an ultrasound index of muscle mass. Muscle strength was similar between the two groups. The variables evaluating microvascular/endothelial function were not different in the two groups, although below reference values. During INCR, V̇O2peak (23.0±4.9 vs. 26.6±6.3 mL/kg/min; p=0.12) and “ventilatory thresholds” were not significantly different in Long COVID vs. CTRL. Signs of inefficiency of pulmonary ventilation (slope of pulmonary ventilation vs. CO2 output greater than >38) and a different ventilatory pattern (greater respiratory frequency, lower tidal volume) were observed in a subgroup (n=4) of Long COVID. Both pulmonary V̇O2 on-kinetics during MOD and V̇O2m-off kinetics following MOD were not different between the two groups
CONCLUSION:
More than two years after an initial infection with the SARS-CoV2 virus, some symptoms belonging to the Long COVID syndrome (i.e. dyspnea, fatigue and exercise intolerance) are still present in some patients. Nevertheless, no differences were observed between Long COVID and CTRL patients for almost all variables evaluating the pathophysiological mechanisms potentially responsible for the symptoms which were investigated. Symptoms may be attributable to other factors (i.e. psychological/neurological) which were not investigated.

(Funding: Italian Ministry of University and Research, PRIN Project 2022LBBKHX)