Background and aim of the study: Studies using transcranial Doppler monitoring have identified high-intensity transient signals (HITS) after mechanical valve replacement. Although cognitive dysfunction in relation to HITS was reported in some studies, the current data basis is inconsistent. The study aim was to investigate the long-term effects of HITS on cognitive function.
Methods: Forty patients who had undergone mechanical valve replacement (mean 5.3 years previously) participated in the study. HITS-measurements were performed on the day of neuropsychological assessment. Patients were allocated to HITS-high and HITS-low groups on the basis of the median HITS-rate. Both patient groups completed a neuropsychological test battery and were compared to healthy controls.
Results: Both patient groups showed verbal and visual memory deficits in comparison with controls.

The HITS-high group scored lower on verbal memory compared to the HITS-low group. In addition, the HITS-high group showed executive deficits when compared to the HITS-low group and controls. The significant effects with respect to verbal memory and executive functions remained after extracorporeal circulation time differences were controlled for.
Conclusion: The study results imply that heart valve replacement with mechanical prostheses may be associated with mild cognitive impairment. The differential impairment pattern of the high- and low-HITS groups further suggests that the number of HITS may be of critical importance. The observed memory impairments were consistent with the view that cognitive dysfunction after valve replacement may be due to temporal lobe dysfunction. However, future studies are required to investigate the association of number of HITS, cerebral changes and cognitive function in further detail.
The Journal of Heart Valve Disease 2005;14:338-343