Squared Coherence Analysis Might Suggest Cerebral Autoregulation Post-Surgery Impairment in Patients Undergoing Surgical Aortic Valve Replacement

Abstract

A squared coherence (K2) approach was applied to investigate cerebral autoregulation (CA) in 33 patients (age: 63±14 yrs; 27 males) undergoing surgical aortic valve replacement (SAVR) before surgery (PRE), after surgery (POST) and after a 3-month follow-up (POST3). K2 was assessed between mean arterial pressure and mean cerebral blood flow velocity in very low frequency (VLF, 0.02-0.07 Hz), low frequency (LF, 0.07-0.15 Hz) and high frequency (HF, 0.15-0.4 Hz) bands at rest in supine position (REST) and during active standing (STAND). The significance of K2 was tested individually via a surrogate approach. Results showed that K2 in HF band increased during POST compared to PRE at REST but this rise was more limited during STAND. Analysis of K2 suggests a possible impairment of CA after SAVR that might expose patients to a higher risk of developing post-surgery cerebrovascular adverse events.