CARDIAC AUTONOMIC CONTROL DURING SLEEP IN PATIENTS WITH MULTIPLE SYSTEM ATROPHY: A PILOT STUDY ON THE IMPACT OF CPAP THERAPY

Objectives To characterize sleep-stage autonomic regulation in multiple system atrophy (MSA) using cardiorespiratory coupling (K2) and symbolic dynamics (0V%, 2UV%, 2LV%) derived from ECG tracings in video‑polysomnography (v‑PSG). The study aims to compare patients with and without sleep‑disordered breathing (SDB) and to assess the acute autonomic effects of CPAP therapy during the second night in patients with SDB. Methods We retrospectively analyzed v‑PSG recordings from MSA patients who underwent evaluation over two consecutive nights at the Pitié Salpêtrière Hospital (Paris). Heart rate (HR), K2, and symbolic dynamics were computed from Wake, NREM, and REM segments. HRV indices were first compared between patients with and without SDB, followed by a secondary analysis stratifying SDB+ patients into specific phenotypes (OSA, isolated stridor, and OSA+stridor). Finally, changes between Night 1 and Night 2 were evaluated in patients treated with CPAP during the second night and compared with a no‑CPAP subgroup. Results At baseline (Night 1), SDB+ patients showed a markedly impaired autonomic profile compared to the noSDB group: K2 was lower across Wake, NREM, and REM. Additionally, the vagal marker 2LV% was reduced in each state, while the sympathetic marker 0V% was selectively higher in REM. Across SDB phenotypes, isolated stridor was associated with specific autonomic vulnerability. Under CPAP treatment in Night 2, SDB+ patients showed a coherent autonomic shift: HR decreased in NREM and REM, 0V% declined in Wake and REM, while 2UV%, 2LV%, and K2 values increased, indicating restored vagal modulation and coupling. The no‑CPAP subgroup showed no consistent night‑to‑night autonomic changes. Conclusions The presence of SDB in MSA is associated with a generalized degradation of heart–breathing coordination and a blunting of vagal structuring, which is most prominent in REM sleep and in patients with stridor. CPAP therapy induces a rapid recalibration toward a more physiological autonomic profile, suggesting that mitigating respiratory load and arousals can restore more coherent cardiorespiratory entrainment.