Cognitive dysfunction after ventricular fibrillation during implantable cardiovertor defibrillator procedures is related to duration of the reperfusion interval

The insertion of implantable cardioverter/defibrillators (ICD) requires induction of repeated episodes of ventricular fibrillation (VF). The neuropsychological repercussions associated with repeated inducement of hypotension and cerebral ischemia are unknown. In this prospective clinical trial, 1 day prior to ICD assessment/implantation and 5 days postprocedure, 14 patients underwent neurological and cognitive screening. Cognitive dysfunction was defined as impaired performance in one of four cognitive domains. Neurological impairment was defined as a decrement of 2 or more points from baseline of a total possible score of 45 points. Intraoperative hemodynamics, including the reperfusion interval (RI; end of preceding fibrillation to beginning of the next), were recorded. Patients underwent an average of 12 +/- 6 episodes of VF with average duration of mean arterial pressure (MAP) <50 mm Hg for 17 +/- 9 s (range 6-39 s)and of MAP <30 mm Hg for 11 +/- 5 s (range 2-22 s). Nine patients, in none of whom the predetermined criteria for neurologic impairment was met, demonstrated a new subtle neurologic finding postoperatively. Ten of 14 patients met the criterion for cognitive dysfunction 5 days postoperatively. The mean RI between episodes of VF was significantly different between those patients demonstrating cognitive dysfunction and the unimpaired patients (3.1 +/- 0.5 min in the group with cognitive dysfunction vs 3.9 +/- 0.8 min in the unimpaired group, P = 0.027). Five patients without cognitive impairment had longer RI between episodes of circulatory arrest than those showing impaired cognition. We conclude that cognitive dysfunction can occur after insertion of ICD and is related to the duration of RI.