Ann Thorac Surg 2005;79:1462
© 2005 The Society of Thoracic Surgeons
Correspondence
Do Off-Pump Surgical Procedures Really Improve Memory?
Ola A. Selnes, PhD
Neurology, Johns Hopkins Hospital, 600 N Wolfe St, Meyer 100, Baltimore, MD 21287, USA
oselnes{at}jhmi.edu
To the Editor:
The Annals contained a very informative article regarding critical evaluation of the medical literature. Ferraris and Ferraris [1] warned us that as many as one third of journal articles may contain errors and that "cautious circumspection" is advised when evaluating the scientific literature.
By coincidence, in the same issue, a study by Lee and colleagues [2] illustrates their point rather nicely. This prospective, randomized study compared the neurological and clinical morbidity after off-pump (OBCAB) versus on-pump coronary artery bypass grafting (CABG). The authors concluded that off-pump procedures may reduce neurological and clinical morbidity. As part of their study, they also examined cognitive performance and found that "compared with base line, OPCAB patients performed better on the Rey Auditory Verbal Learning Test [RAVLT] (total and recognition scores) at both 2 weeks and at 1 year (p 
0.05), whereas CABG performance was statistically unchanged for all cognitive measures."
On the surface, this summary of their finding is likely to create the impression that on measures of memory performance, the off-pump group clearly did better than the conventional on-pump group. The authors suggested that one possible interpretation of their findings is that "the lack of improved performance on the RAVLT over time, in the CABG group, may represent a relative cognitive decline or a deficit in the ability to learn the RAVLT." They further speculated that their single photon emission computed tomographic findings of "reduced left temporal lobe perfusion may underlie the relatively poorer performance on the RAVLT in those patients undergoing CABG."
Inspection of the actual data presented in Table 3 of the report by Lee and associates suggests that there may be a more parsimonious explanation for the "improved" memory performance in the off-pump group. The mean baseline RAVLT (Total) score for the off-pump group is 3.1 points lower than that for the on-pump group. This, combined with slightly less variability in memory test performance (smaller standard deviations) in the off-pump group, may have accounted for the significant "greater improvement" in this group. The mean RAVLT scores for the on-pump group are not only higher at baseline but also are consistently higher at the 2-week and 1-year follow-up points. Therefore, there appears to be no compelling evidence, on the basis of the data presented in Table 3, that the on-pump group is any worse off in terms of overall memory performance after CABG. This is also consistent with the authors' report of no difference in the incidence of cognitive decline between the on-pump and off-pump groups either at 2 weeks or 1 year.
 |
References
|
|---|
- Ferraris VA, Ferraris SP. Assessing the medical literature: let the buyer beware. Ann Thorac Surg. 2003;76:4–11[Abstract/Free Full Text]
- Lee JD, Lee SJ, Tsushima WT, et al. Benefits of off-pump bypass on neurologic and clinical morbidity: a prospective randomized trial. Ann Thorac Surg. 2003;76:18–26[Abstract/Free Full Text]
Top
References