Postoperative cognitive deficits following cardiac surgery: neurobehavioral assessment, neuroimaging contributions, and cognitive training

Every year, a substantial number of patients undergoing cardiac surgery experience postoperative cognitive deficits, a condition characterized by impairments in attention, executive functions, memory, and processing speed that may persist for weeks, months, or even longer. These cognitive alterations profoundly affect daily life, but their consequences vary depending on age and personal environment. In working-age adults, postoperative cognitive deficits may compromise professional autonomy, multitasking abilities, decision- making, and stress management, potentially jeopardizing employment stability and quality of life. In older adults, postoperative cognitive deficits often exacerbate pre-existing vulnerabilities, contributing to loss of independence, reduced social engagement, and increased risk of long-term cognitive decline. Understanding characteristics of these disorders and which factors interfere with their complete recovery is crucial for designing targeted assessments and rehabilitation strategies. In the first part of this thesis, I established a comprehensive theoretical framework describing postoperative cognitive deficits within the broader heart–brain connection. Neuropsychological, neuroimaging, and rehabilitative perspectives have been integrated to delineate a broad and critical overview of postoperative cognitive deficits. Subsequently, based on this framework, a systematic review provided a quantitative and comparative analysis of ischemic lesions reported in the literature. Through a rigorous selection of clinical cases with available neuro-radiological images and the use of lesion- mapping tools compared against control datasets, the review identified recurrent patterns of functional disconnection involving occipital, thalamic, and fronto-medial regions. These findings complemented the clinical evidence reviewed in the previous chapter and suggested that some brain regions and functional connections may be more frequently involved after cardiac surgery. The general overview and the reviews laid the foundations of the pilot study design comparing healthy controls and cardiac surgery patients to develop an early neuropsychological screening protocol for the detection of postoperative cognitive deficits. Results identified cognitive difficulties across multiple domains in patients assessed during the early postoperative period. Patients showed reduced working memory, impaired cognitive flexibility, and difficulties in planning and inhibitory control, indicating a predominantly executive pattern of cognitive vulnerability. Visuospatial impairments emerged through significantly poorer Clock Drawing Test performance despite normal global cognition on the MMSE, reinforcing the selective vulnerability of executive–visuospatial circuits. Additionally, reduced processing speed, orientation difficulties, and altered vigilance indicated broader attentional difficulties during the early postoperative period. Psychological assessments revealed elevated levels of anxiety, depression, and stress, highlighting the relevance of emotional factors during early postoperative recovery. Correlation analyses indicated that higher anxiety levels were associated with poorer working memory performance, suggesting a potential relationship between emotional distress and cognitive functioning in the early postoperative period. Given the relevance of these results, a longitudinal interventional study was conducted to evaluate the clinical utility of standardized neuropsychological screening and targeted cognitive rehabilitation in the postoperative trajectory. A total of 123 screened and enrolled patients were randomly allocated to two groups (n = 62 in the intervention group and n = 61 in the control group). Following enrolment, N = 4 patients were excluded (three patients provided informed consent but were urgently transferred to another facility, and one patient withdrew during the neuropsychological assessment). This resulted in a final sample of N = 119 patients, with n = 62 in the intervention group and n = 57 in the control group. All participants who provided consent underwent a brain MRI to detect silent cerebral ischemia and evaluate its potential impact on rehabilitation interventions. The intervention protocol was designed to reduce the functional impact of postoperative deficits, enhance recovery of executive and attentional functioning, and evaluate treatment effectiveness at multiple time points. Results showed heterogeneous but overall progressive cognitive recovery trajectories across domains. Executive–visuospatial abilities and processing speed/attention demonstrated an early improvement followed by stabilization, whereas working memory and verbal episodic memory exhibited a slower and more prolonged recovery extending to later follow- up stages. Recovery patterns were strongly influenced by baseline vulnerability profiles, with high-vulnerability patients showing larger gains over time despite lower initial performance. Cognitive rehabilitation did not significantly modify recovery trajectories across all domains but was associated with higher overall performance in verbal fluency and verbal episodic memory, suggesting a possible domain-specific contribution. These findings suggest that postoperative cognitive recovery may reflect the combined contribution of spontaneous recovery processes, individual cognitive reserve, and rehabilitation. This thesis examines cognitive deficits after cardiac surgery by considering neuropsychological, psychological, and neuroimaging findings together, with particular attention to individual vulnerability and postoperative recovery. Because preoperative neuropsychological assessments were not available, the present work could not directly investigate postoperative cognitive dysfunction (POCD) according to its formal definition, which requires comparison with preoperative baseline performance. Instead, the study focused on the identification and characterization of cognitive deficits observable in the postoperative period. The findings support early, domain-specific neuropsychological assessment after cardiac surgery and suggest that follow-up should take individual cognitive and emotional vulnerability into account. They also indicate that postoperative cognitive recovery varies across patients and cognitive domains, supporting the need for individualized monitoring and rehabilitation.