McKhann GM et al. (2005) Is there cognitive decline 1 year after CABG? Neurology 65: 991–999

Coronary artery bypass grafting (CABG) is commonly thought to cause a decline in the postoperative cognitive functioning of patients. McKhann and colleagues, however, have recently reported results of a study that casts doubt on this claim.

The four-arm, prospective study investigated CABG patients (n = 140), patients undergoing off-pump coronary surgery (n = 72), nonsurgical cardiac controls with diagnosed coronary artery disease (n = 99), and heart-healthy controls with no cardiac risk factors (n = 69). Participants underwent a series of neuropsychological tests at baseline (before surgery), 3 months and 12 months. Scores from the tests were combined to form eight cognitive domain scores for cognitive abilities such as verbal memory and psychomotor speed.

Baseline performances of heart-healthy controls were found to be higher than those of the other three groups for all cognitive domains. For six of the domains, the difference between the performances of the healthy controls and the two surgical groups was significant (P <0.01). All groups showed a similar degree of improvement in intrasubject scores from baseline to 3 months, and from 3 to 12 months. At 12 months all groups were performing at or above their baseline levels.

Concluding that there was no evidence that CABG patients' cognitive performance was worse than that of control patients with coronary artery disease over a 12-month follow-up period, the authors suggest that, in general, patients with long-standing coronary artery disease have an element of cognitive impairment caused by cerebrovascular disease, and that this is present before they undergo surgery.