Cerebral oxygenation during defibrillator threshold testing of implantable cardioverter defibrillators.
BACKGROUND
The induction of ventricular fibrillation (VF) during defibrillator threshold testing of implantable cardioverter defibrillators (ICD) provokes global cerebral hypoperfusion and impaired oxygen delivery. Limited data are available on the neurophysiological effects of defibrillator threshold testing. Near infrared spectroscopy (NIRS) can noninvasively measure changes in specific chromophores, which reflect cerebral oxygenation at the intravascular and mitochondrial levels. We performed a prospective trial using NIRS to analyze cerebral cortical oxygenation during defibrillator threshold testing.


METHODS
Eleven patients (men = 9; age = 64 +/- 11 years: LVEF = 44 +/- 11%) underwent subpectoral ICD implantation and defibrillator threshold testing under general anesthesia. A NIRO 300 spectrometer was used to measure the absolute changes in the concentrations of oxyhemoglobin, de-oxyhemoglobin, and cytochrome c oxidase copper moiety during each procedure. The mean arterial blood pressure was monitored simultaneously.


RESULTS
The mean number of defibrillator threshold tests was two (range 2-6). Twenty-six episodes of VF (duration 13.1 +/- 9.7 seconds; cycle length 230.2 +/- 20.8 ms) and two episodes of VT (duration 15 +/- 2.8 seconds; cycle length 320 +/- 11.3 ms) were induced. Each episode of VF and VT resulted in a decrease in the mean arterial blood pressure to 23.9 +/- 7.5 mmHg (p < or = 0.05) and oxyhemoglobin (-4.2 +/- 1.7 micromol/L; p < or = 0.05) and an increase in de-oxyhemoglobin (2.7 +/- 1.4 micromol/L). There was no change in the cytochrome c oxidase copper moiety redox status (0.09 +/- 0. 30 micromol/L).


CONCLUSIONS
Our results suggest that impaired oxygen delivery during induced VF and VT does not affect oxygen availability at the cellular intra-mitochondrial level.
McNeill
Elizabeth
E
Division of Cardiology, Department of Medicine, The University of British Columbia, Vancouver, BC, Canada.
Gagnon
Roy E
RE
Potts
James E
JE
Yeung-Lai-Wah
John A
JA
Kerr
Charles R
CR
Sanatani
Shubhayan
S
D001921:Brain / Q000378:metabolism*; D017147:Defibrillators, Implantable; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D011446:Prospective Studies; D019265:Spectroscopy, Near-Infrared
D010100:Oxygen