The incidence of delirium following cardiac surgery is highly variable, ranging between 3-32% depending on the study. Among patients over 60, this incidence can rise to 50-70%. These figures require cautious interpretation due to heterogeneity in delirium diagnosis and assessment across studies. Risk factors such as a history of cerebrovascular disease, stroke, dementia, advanced age, alcohol use, renal disease, liver failure, and thyroid abnormalities increase the brain’s vulnerability to this complication. Anesthesia policies, sedative agents, and opioid use also play a role in delirium onset, making it challenging to attribute this complication solely to surgical procedures.

The article analyzed today is a prospective, observational, single-center study comparing patients over 70 years treated surgically for aortic valve disease versus percutaneous treatment. The study aimed to assess postoperative delirium incidence and subsequent impact on quality of life. Patients were recruited from September 2018 to January 2020. The primary event was daily delirium assessment over the first five postoperative days, conducted by specially trained personnel through various questionnaires. Secondary events included perioperative inflammation (measured by C-reactive protein), postoperative complications, quality of life (EuroQol-5 questionnaire), and six-month mortality. Given the heterogeneity of the two population groups, a weighted inverse probability adjustment was applied, considering EuroSCORE II, age, and frailty.

A total of 250 patients were included, with 166 patients treated surgically and 84 percutaneously. The mean age was of 80 years, with an average EuroSCORE II of 5 points. Following the weighted inverse probability adjustment, it was observed that the surgical group exhibited a higher incidence of postoperative delirium: 51% versus 15% (p < 0.0001). The surgical group also experienced greater perioperative inflammation, deeper anesthetic sedation, and more intraoperative hypotension events. Nevertheless, despite the higher incidence of postoperative delirium, at six months, 41% of surgically treated patients reported improved quality of life compared to 12% in the percutaneous group (p < 0.0001). Within the surgical group, those operated via median sternotomy were compared to those undergoing minimally invasive techniques, with no statistically significant differences observed.

The authors concluded that transcatheter techniques are associated with a lower incidence of postoperative delirium, but surgical valve replacement provided greater long-term quality-of-life benefits. Hoogma et al. advocate for incorporating these variables into Heart Team decision-making to determine the optimal treatment for patients.

COMMENTARY:

The etiology of delirium following surgical procedures is multifactorial, influenced by inherent patient risk factors, surgical specifics, and anesthesia protocols. Regarding surgery-specific factors, particularly in cardiac surgery, several hypotheses attempt to explain the high delirium incidence. Cardiopulmonary bypass use and surgical stress trigger systemic inflammation, with studies linking elevated C-reactive protein (CRP) levels, an unspecific biomarker, as an independent risk factor for postoperative delirium. In line with inflammation and surgical stress, prolonged operative times are also associated with higher delirium incidence. Similarly, significant perioperative hypotensive events induce cerebral injury and may trigger postoperative delirium. Such hypotensive events must be substantial enough for cerebral autoregulation mechanisms to fail in compensating for blood pressure drops. However, literature offers mixed findings on the association between perioperative hypotension and delirium incidence. Lastly, anesthetic depth appears to play a critical role in this neurological complication. Indeed, in the percutaneous group, patients requiring deep sedation had the highest postoperative delirium incidence. Surgical valve replacement generally necessitates deeper anesthetic sedation than the percutaneous technique, as evidenced by the high proportion of surgical patients with a BIS below 40 during the procedure.

The study’s limitations complicate the interpretation of its results for clinical practice. Starting with design limitations that affect its internal validity—single-center, non-randomized, and two non-comparable population groups despite weighted inverse probability adjustment. The percutaneous group had a higher EuroSCORE II, indicating more comorbid and frail patients. Frailty limits perceived quality of life and could explain the low improvement rate in six-month questionnaires. The surgical group included patients with concomitant revascularization and ablation procedures, prolonging cardiopulmonary bypass times and surgical aggression, directly related to delirium incidence. Furthermore, a significant percentage of percutaneously treated patients were discharged before the five-day period established for postoperative delirium detection, likely overestimating the difference noted by researchers.

In conclusion, this study, while having the strengths of a prospective design and comprehensive delirium assessment, has significant weaknesses that affect its internal validity and limit the extrapolation of results to clinical practice. We do agree, however, on valuing the perceived quality of life of our patients post-procedure. Quality-of-life measurement through various parameters should be a mandatory item for discussion in Heart Teams before any decision-making.

REFERENCE:

Hoogma DF, Venmans E, Al Tmimi L, Tournoy J, Verbrugghe P, Jacobs S, et al. Postoperative delirium and quality of life after transcatheter and surgical aortic valve replacement: A prospective observational study. J Thorac Cardiovasc Surg.2023 Jul;166(1):156-166.e6. doi: 10.1016/j.jtcvs.2021.11.023.