Background
Persistent symptoms after the acute SARS-CoV-2 infection are referred to as post-COVID-19 syndrome(PCS). Fatigue, palpitations and exercise intolerance are common complains among PCS patients in whom unexplained sinus tachycardia is a frequent observation.
Objective
To evaluate the prevalence and the pathophysiological mechanisms of IST in a consecutive and prospective population of patients with PCS.
Methods
Consecutive patients with persistent symptoms 3 months after an acute COVID-19 were prospectively evaluated at a multi-disciplinary PCS unit. All patients were screened for IST and those with confirmed criteria underwent comprehensive CV examination: ECO, 24h Holter (assessment of the cardiac autonomic function), QoL Questionnaire (MLHFQ), six-min walking test (6MWT) and blood sample with inflammation and myocardial biomarkers. Two control patients, matched by age and gender, were assigned to each case: one with previous SARS-CoV-2 infection without PCS (group 2,recovered asymptomatic) and one without prior COVID (group 3,uninfected).
Results
IST were met in 43/200 PCS patients (21%) being more common in young (mean age 39y) woman (91%) without clinical history and with mild COVID (not requiring hospital admission during the acute phase). Mean HR 96±3 (supine) and 112±17 (upright position), with 8 patients fulfilling diagnostic of POTS. No underlying structural heart disease, proinflammatory state, myocyte injury or hypoxia were identified 6MWT showed a significantly diminished exercise capacity(59% of the estimated distance). An impaired QoL was also identified. Regarding the 24h Holter, all HRV parameters were significantly deteriorated in IST patients compared with control groups (significantly decrease in time and frequency domain parameters). The most reduced components were those related with the cardiovagal tone: PNN50 4±4 in group 1 (vs 11±9 in group 2 and 18±9 in group 3; p<0 002);HF band 336±280 (vs 823±1200 in group 2 and 1229±630 in group 3; p=0 01).
Conclusion
IST is a prevalent condition among PCS patients and may at least partially explain the prevalent symptoms of fatigue, impaired exercise, and palpitations, Cardiac ANS imbalance with decreased parasympathetic activity may account as a plausible explanation.