Cognitive impairment after appropriate implantable cardioverter-defibrillator therapy for ventricular fibrillation

Short periods of cerebral ischaemia during ventricular defibrillation testing may be associated with neuropsychological impairment. However, the impact of out-of-hospital ventricular fibrillation (VF) converted by implantable cardioverter-defibrillator (ICD) shock on cognitive functioning is unknown.

To assess the impact of out-of-hospital VF converted by ICD shock on cognitive functioning.

The study included 52 primary prevention ICD recipients. Patients with a history of stroke or other neurological impairment, previous head injury and individuals unable to see or speak to complete neuropsychological tests were not included.Initially, a Mini-Mental State Examination was performed in all patients and one patient with a result below 24 points was excluded from the study. The cognitive battery consisted of four tests (six measurements): 1) the Digit Span subtest of Wechsler Adult Intelligence Scale-Revised; 2) the Digit Symbol subtest of Wechsler Adult Intelligence Scale-Revised; 3) the Halstead-Reitan Trail-Making Test A and B; and 4) the Ruff Figural Fluency Test.

The mean time from ICD implantation to cognitive assessment was 26 months. During this period, 15 appropriate shocks for VF were observed in seven (14%) patients. The patients with appropriate ICD therapy were significantly worse in two out of the six neuropsychological measurements and had a significantly lower aggregate result. In multivariate linear regression analysis, defibrillation therapy was an independent factor of poor cognitive functioning, along with age and education.

Short periods of out-of-hospital VF converted by ICD are associated with cognitive impairment in the recipients of primary prevention ICD.