CEREBRAL-ISCHEMIA DURING IMPLANTATION OF AUTOMATIC DEFIBRILLATORS

In order to study the influence of repetitive episodes of ventricular fibrillation (VF) during defibrillator implantation on the electrical activity of the brain, we performed an electroencephalographic (EEG) m onitoring during implantation procedure in 18 patients. For defibrilla tion threshold testing 62 episodes of VF (1-6 episodes per patient) we re induced, The mean duration of hypotension during an episode (define d as a mean arterial pressure of 50 mm Hg or less) was 33 +/- 16 s. EE C monitoring was performed using the International 10-20 System, The d uration of cardiac arrest-related EEG alteration was assessed by an ex perienced neurologist and could be determined in 41 test-episodes; in 21 episodes analysis was not possible due to poor recordings, Ischemia -related EEG changes started 7.8 +/- 4.6 s after VF induction and last ed 64 +/- 49 s (range, 12-240). The duration of EEG alteration was sig nificantly (p < .001) correlated with the duration of VF episodes (r = .71) and the associated hypotension (r = .82). With regard to patient s the duration of ischemia related EEC changes also correlated signifi cantly (p = .001) with the individual cumulative duration of VF (r = . 85) and the associated hypotension (r = .88), In females EEG changes l asted longer than in males (p = .03); this finding, however, was only based on 2 women. Other clinical parameters, such as patient age, degr ee of congestive heart failure, left ventricular ejection fraction, st roke volume and cardiac index, the order of episodes within the testin g sequence, and the time interval between episodes did not correlate w ith the duration of EEG alteration after VF induction, The duration of ischemia-related EEG alteration during VF episodes depends on the dur ation of cardiac arrest. In females EEG changes tended to last longer than in males, however, this finding has to be confirmed. An associati on with Ether clinical parameters has not been observed, Limitation of VF duration appears to be the most important factor to avoid prolonge d cerebral ischemia.