Ann Thorac Surg 2007;84:358
© 2007 The Society of Thoracic Surgeons
Correspondence
Assessment of Neurocognitive Outcome After Cardiac Surgery
Sharif Al-Ruzzeh, PhD, FRCS,
David O’Regan, MD, FRCS C-Th
The Yorkshire Heart Centre, Leeds General Infirmary, Great George St Leeds, LS1 3EX United Kingdom
(Email: sharifalruzzeh{at}hotmail.com; david.o'regan{at}leedsth.nhs.uk).
To the Editor:
We read with interest the report on the randomized controlled trial performed by Ernest and colleagues [1] to assess neurocognitive outcomes after off-pump versus on-pump surgery. Despite the fact that the authors stated more than once in the report that they planned and performed the study in accordance with the Consensus Statement [2], they actually did not fully comply with it. Therefore the presented data in the report may not completely support the conclusions reached due to the following issues:
- 1 The consensus states that the performance of neuropsychologic tests can be influenced by mood state variations, and therefore it is important that mood state assessments are performed concurrently with the neuropsychologic assessments [2]. The report does not mention any assessment of the mood state of the recruited patients at any of the time points nor acknowledge its possible effects on the results. Anxious patients were recently shown to suffer neurocognitive dysfunction after off-pump surgery in isolation of all other factors [3]. Furthermore, quality of life assessment, despite the fact that it is not discussed in the consensus, has recently become an important factor to be considered alongside neurocognitive assessment. Neurocognitive dysfunction after cardiac surgery has been shown to be associated with lower general health and a less productive working status [4].
- 2 The consensus also states that the investigators should take in account the new events that may occur in the days after the operation. This would certainly include the occurrence of any postoperative complications. We failed to find any other report by the same group on the clinical outcomes of the patients recruited in the trial. We believe it would have been rather more useful to present the clinical outcome concurrently, particularly, in the course of a trial aiming to compare two surgical techniques. Taking atrial fibrillation as only one example, there is a recent evidence that its occurrence postoperatively can cause neurocognitive dysfunction both after off-pump surgery [3] and on-pump surgery [5] to varying degrees.
- 3 The consensus also states that the individual changes in performance from baseline are essential to any evaluation of the impact of the operation or any intervention associated with it [2]. Without entering into statistical details, a method of score analysis by calculating score change from baseline and then comparing mean score changes between the group of concern and another control group using analysis of covariance was strongly recommended by experts to be the way forward for the assessment of this type of data [6]. We agree with the authors that there are major disadvantages of the single-case definitions, such as a decline of one standard deviation or 20% change. This is because high baseline performers will be more likely to be classified as having deteriorated, even in the absence of real change due to the phenomenon of "regression to the mean" [6]. This concept has been recently used by us [7] and previously in large multicenter trials [8].
We believe that a degree of caution and systemization should be applied in the assessment and reporting of neurocognitive function after cardiac surgery, particularly, in randomized controlled trials.
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References
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- Ernest C, Worcester M, Tatoulis J, et al. Neurocognitive outcomes in off-pump versus on-pump bypass surgery: a randomized controlled trial Ann Thorac Surg 2006;81:2105-2114.[Abstract/Free Full Text]
- Murkin J, Newman S, Stump D, Blumenthal J. Statement of consensus on assessment of neurobehavioral outcomes after cardiac surgery Ann Thorac Surg 1995;59:1289-1295.[Free Full Text]
- Sendelbach S, Lindquist R, Watanuki S, Savik K. Correlates of neurocognitive function of patients after off-pump coronary artery bypass surgery Am J Crit Care 2006;15:290-298.[Abstract/Free Full Text]
- Newman M, Grocott H, Mathew J, et al. Neurologic Outcome Research Group and the Cardiothoracic Anesthesia Research Endeavors (CARE) Investigators of the Duke Heart Center Report of the substudy assessing the impact of neurocognitive function on quality of life 5 years after cardiac surgery Stroke 2001;32:2874-2881.[Abstract/Free Full Text]
- Stanley T, Mackensen G, Grocott H, et al. Neurological Outcome Research Group and the CARE Investigators of the Duke Heart Center The impact of postoperative atrial fibrillation on neurocognitive outcome after coronary artery bypass graft surgery Anesth Analg 2002;94:290-295.[Abstract/Free Full Text]
- Browne S, Halligan P, Wade D, Taggart D. Cognitive performance after cardiac operation: Implications of regression toward the mean J Thorac Cardiovasc Surg 1999;117:481-485.[Abstract/Free Full Text]
- Al-Ruzzeh S, George S, Bustami M, et al. Effect of off-pump coronary artery bypass surgery on clinical, angiographic, neurocognitive, and quality of life outcomes: randomised controlled trial BMJ 2006;332:1365.[Abstract/Free Full Text]
- Wahrborg P, Booth J, Clayton T, et al. SoS Neuropsychology Substudy Investigators Neuropsychological outcome after percutaneous coronary intervention or coronary artery bypass graftingResults from the Stent or Surgery (SoS) trial. Circulation 2004;110:3411-3417.[Abstract/Free Full Text]
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- Christine Ernest, Marian Worcester, James Tatoulis, Peter Elliott, Barbara Murphy, Rosemary Higgins, Michael Le Grande, and Alan Goble
Ann. Thorac. Surg. 2007 84: 358-359.
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C. Ernest, M. Worcester, J. Tatoulis, P. Elliott, B. Murphy, R. Higgins, M. Le Grande, and A. Goble
Reply
Ann. Thorac. Surg.,
July 1, 2007;
84(1):
358 - 359.
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