Pre-existing cognitive impairment as a factor influencing outcome after cardiac surgery

Conventional methodology to investigate cognitive impairment after coronary artery bypass graft (CABG) surgery leaves unclear the potential for pre-existing cognitive deficits to influence outcome. Individuals with pre-existing deficits may be more vulnerable to the effects of CABG, hence biasing the results of a typical prospective trial if account is not taken of their state. The present study examined the effect of pre-existing cognitive impairment upon cognitive outcome in 81 patients undergoing CABG. Patients performed the Stroop Neuropsychological Screening Test and other psychometric assessments prior to and at 6 days and 6 months after CABG. Those with pre-existing cognitive deficits were significantly more likely to display impairment at 6-day and 6-month follow-ups than were those without pre-existing deficits. Greater age and lower pre-morbid intelligence were also significant predictors of post-CABG deficit, confirming earlier findings. The results imply both that pre-existing cognitive impairments may render patients more vulnerable to post-operative deficits and that, in the absence of such pre-existing impairments, CABG surgery does not inevitably lead to later deficits. The study also replicated previous findings showing a similar influence of pre-existing depression upon emotional state after CABG. Overall, the results confirm the importance both of a patient's pre-existing cognitive and emotional states, and the methodology to assess them, in influencing outcome after cardiac surgery and the conclusions to be drawn as to the supposed adverse effects of the procedure.