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Eur J Cardiothorac Surg 2003;24:666
© 2003 Elsevier Science NL

Letter to the Editor

Reply to Jahangiri and Motallebzadeh

Department of Cardio-Thoracic Surgery, Vienna General Hospital, University of Vienna, Waehringer Guertel 18–20, A-1090 Vienna, Austria

Received 11 June 2003; accepted 11 June 2003.

^* Corresponding author. Tel.: +43-1-40400-5620; fax: +43-1-40400-5640
e-mail: michael.grimm{at}akh-wien.ac.at

Key Words: Neurocognitive deficit • Mitral valve • Extracorporal circulation • Cognitive P300 potentials

As stated in the article the aim of the study was to objectively measure neurocognitive function in patients undergoing mitral valve replacement/repair. The simple question was, to obtain more detailed information about neurocognitive outcome of selected surgical subgroups. In this specific question, we were – of course – aware about the fact that patients differ with regard to preoperative diagnoses. Since these different diseases have different treatment standards, randomization was not possible and the latter fact has been seriously addressed in the present paper. Of course patients with stenosis or mixed, calcific mitral valve disease are more likely to exhibit embolic mediated cerebral injury as compared to patients with valve insufficiency. This has also been addressed.

As stated in the paper, mean arterial pressure (on-pump) was vigorously kept above 50 mmHg. We do not provide any data on level of education. The main reason for this is that results obtained by the used diagnostic tool – in contrast to frequently used psychometric test batteries – do not depend on level of education. Certainly a merit of the used tool.

There should be no doubt about the usefulness and appropriateness of the used diagnostic tool. Cognitive P300 auditory evoked potentials have previously been used to measure neurocognitive function in various metabolic disorders, patients undergoing heart transplantation and patients undergoing open heart surgery [1,2]. Cognitive P300 auditory evoked potential are the result of an activation of a widespread network of cortical structures, including association areas in the parietal, temporal and prefrontal cortex, as well as the hippocampus [3]. As a result of the involvement of many brain regions in the P300 generation, the P300 can be used as a general indicator for neurocognitive function [4]. In contrast to standard psychometric tests batteries the used diagnostic tool lacks biases such as long performance times (stressing attention), visual impairment, influence of psychomotor function, level of education and learning effects. The latter are of particular interest for follow-up studies – especially in elderly, in part multimorbid patients. P300 peak latencies, were shown to be related to cognitive impairment rating, rapid evaluation of cognitive function tests, orientation, stimulus evaluation, selective attention, visual pattern recognition, and digit span and were shown to be much more sensitive in detecting neurocognitive deficit than psychometric tests or electroencephalograms. Moreover, the P300 technique has a very low intraindiviual test-retest variability with a coefficient of variation of 2%, which further stresses its usefulness for cognitive follow-up studies [5]. Mini Mental State examination was used to rule out that all patients entering the study were free from clinically overt neurological disorders and dementia.

Based on the scientifically well-documented technique of cognitive P300 auditory evoked potentials, our only intention was to show that there is different neurocognitive outcome in typical patients receiving either mitral valve replacement or mitral valve repair, independent from the fact that these patients do not differ in other patient demographics than valve pathology. Conclusions drawn from this finding may certainly serve as basis for simulative discussion on potential mechanisms and future clinical implications.

References

1. Zimpfer D., Czerny M., Kilo J., Kasimir M.T., Madl C., Kramer L., Wieselthaler G.M., Wolner E., Grimm M. Cognitive deficit after aortic valve replacement. Ann Thorac Surg 2002 Aug;74(2):407-412.[Abstract/Free Full Text]
2. Engelhardt W., Dierks T., Pause M., Sold M., Hartung E., Silber R. P300-mapping – a neurophysiological tool to quantify cerebral dysfunction after coronary artery bypass grafting. Eur J Cardiothorac Surg 1995;9(1):12-17.[Abstract]
3. Kiehl K.A., Laurens K.R., Duty T.L., Forster B.B., Liddle P.F. Neuronal sources involved in auditory target detection and novelty processing: an event related fMRI study. Psychophysiology 2001;38:133-142.[CrossRef][Medline]
4. Polich J., Ehlers C.L., Otis S., Mandell A.J., Bloom F.E. P300 latency reflects the degree of cognitive decline in dementing illness. Electroenceph clin Neurophysiol 1986;63:138-144.[CrossRef][Medline]
5. Grimm G., Stockernhuber F., Schneeweiss B., Madl C., Zeitlhofer J., Schneider B. Improvement of brain function in hemodialysis patients treated with erythropoietin. Kidney Int 1990 Sep;38(3):480-486.[Medline]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Michael Grimm Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Grimm, M. Articles by Zimpfer, D. Search for Related Content PubMed Articles by Grimm, M. Articles by Zimpfer, D. Related Collections Extracorporeal circulation Valve disease