Older Adults' Recovery Dynamics After Cardiac Surgery

Clinical, Functional, and Biological Characterization of Resilience in Older Adults Undergoing Cardiac Surgery: ODYSSEY Study - Pilot Phase

Population aging has increased the number of older adults exposed to interventions with high physiological demand, which are associated with frequent adverse outcomes such as delirium, organ dysfunction, and delayed functional recovery. Current clinical tools, such as frailty assessments, help identify higher-risk populations but do not adequately explain the marked individual variability in recovery or accurately predict who will develop complications. This variability may be partly explained by individual resilience, defined as the ability to recover toward, return to, or even surpass a prior functional state after an acute stressor. Evidence suggests that biological mechanisms related to aging influence resilience; however, biomarkers and integrated clinical models capable of characterizing and potentially modulating resilience in humans remain limited. Therefore, a standardized clinical platform is needed to characterize physiological resilience and its determinants, generating actionable knowledge to improve risk stratification, guide interventions, and optimize recovery in older adults.

To this end, a single-center prospective cohort study will be conducted at Clinica Bicentenario Santiago, including individuals aged ≥65 years who are independent or have mild dependency and are undergoing elective cardiac surgery requiring sternotomy for valvular and/or coronary artery disease, recruited between 2026 and 2027. Participants will undergo a baseline assessment 2-3 weeks before surgery; an early postoperative assessment focused on the systematic recording of clinical outcomes, including delirium and organ dysfunction; and longitudinal follow-up to characterize recovery after discharge. Follow-up assessments will include frailty, intrinsic capacity (the composite of an individual's physical and mental capacities across the cognitive, locomotor, psychological, vitality, and sensory domains), functional status, health-related quality of life, and perceived fatigability, according to the prespecified assessment schedule.

In addition, blood samples will be collected at three time points (baseline, 24 hours postoperatively, and one month after surgery) to measure plasma levels of growth differentiation factor 15 (GDF-15), a biomarker associated with aging-related biological stress and systemic responses to tissue injury. It is projected that at least 75 participants will be recruited over a 12-month period, allowing characterization of baseline clinical and functional profiles, the frequency of postoperative complications and organ dysfunction, trajectories of recovery, and associations between baseline characteristics, biological markers, and subsequent recovery outcomes.

Inclusion Criteria:

• Older adults (≥ 65 años) undergoing elective cardiac surgery via median sternotomy, including coronary artery bypass grafting (CABG) and/or valvular surgery.
• Independence in basic daily activities, defined as a Barthel Index score ≥80.

Exclusion Criteria:

• Emergency surgery for any indication
• Terminal illness, defined as a life expectancy of less than 12 months
• History of cognitive impairment, defined as a documented diagnosis of dementia and/or current treatment with memantine or donepezil
• Advanced hepatic or renal failure, defined as Child-Pugh class C liver disease or chronic dialysis