Cognitive Impairment Before Cardiac Surgery: A Prospective Single-Center Observational Analysis

Abstract

Background/Objectives: We aimed at evaluating the prevalence of cognitive impairment before cardiac surgery, its associated risk factors, and the diagnostic performance of cognitive tests. Methods: This prospective, single-center observational study included patients aged 50 years or older with coronary artery and/or valvular heart disease waiting for cardiac surgery. Patients underwent a cognitive and physical assessment before cardiac surgery. The cognitive assessment included eight tests exploring different cognitive domains and two questions exploring subjective cognitive complaints. Physical assessment included functional capacity and physical activity level. Cognitive tests with adjusted scores below 1.5 or more standard deviations from cognitively unimpaired subjects were considered abnormal. Cognitive impairment was defined as two or more abnormal cognitive tests. Results: We identified objective cognitive impairment in 41 out of 134 patients (31%). Interestingly, 66% of patients with objective cognitive impairment did not report any complaints. Moreover, similar complaints were reported among patients with and without objective cognitive impairment. The combination of Phonetic Fluency Test, Trail Making Test B, Digit Modalities Test, and the digit span forwards from the Wechsler Adult Intelligence Scale yielded the best diagnostic accuracy (AUC: 0.88; 95 CI: 0.82-0.93). Finally, cognitive impairment was associated with a worse Sit-To-Stand performance. Conclusions: Objective cognitive impairment before cardiac surgery is prevalent but subjective cognitive complaints are unreliable. We propose a combination of four cognitive tests with an efficient diagnostic profile to enhance its clinical applicability.

Keywords: cardiac surgery; perioperative cognitive disorders; physical fitness; preoperative assessment.

Figure 1

Study flowchart.

Figure 2

Distribution of cognitive complaints among patients with and without cognitive impairment. Cognitive impairment defined as two or more tests, excluding MMSE, scoring 1.5 standard deviation below normative expectations.

Figure 3

Percentage of patients scoring 1.5 standard deviation below normative expectations across the eight cognitive tests. Tests in purple asses executive/attentional functions, test in green assesses memory, and test in orange assesses language. M@T, Memory Alteration Test; WAIS-DS-F, WAIS Digit Spain Forwards; WAIS-DS-B, WAIS Digit Span Backwards; TMT-A, Trail Making Test A; TMT-B, Trail Making Test B; SDMT, Symbol Digit Modalities Tests; SF, Semantic Fluency; PF, Phonetic Fluency.

Figure 4

Combination of tests with the best diagnostic accuracy. (A). Different combination of tests until reaching the widest AUC at RUN 4. Notice that adding a fifth test does not increase the AUC at Run 5. (B). ROC curve of the best combination of tests. Continuous blue line for RUN 4. Orange line is the reference value for AUC 0.5. AUC, Area under curve; PF, Phonetic Fluency; TMT B, Trail Making Test B; SDMT, Symbol Digit Modalities Tests; WAIS-DS-F, WAIS Digit Span Forwards; M@T, Memory Alteration Test; SF, Semantic Fluency.