Cerebral blood flow velocity during induced ventricular fibrillation and ventricular tachycardia in humans

Mean cerebral blood flow velocity (CBFVMCA) and mean cerebral perfusion pressure (CPP) were investigated in five patients undergoing placement of an implantable cardioverter/defibrillator during 30 periods of induced pulseless ventricular tachycardia (VT) or induced ventricular fibrillation (VF) with a duration from 4 seconds to a maximum of 47 seconds. During VT (n=6) CBFVMCA decreased from 42 cm/sec (range: 32-60) to 20 cm/sec (range: 17-28) and during VF (n=24) it decreased from 44 cm/sec (range: 28-75) to 13 cm/sec (range: 10-15). CPP decreased from 66 mm Hg (range: 60-72) to 30 mm Hg (range: 27-38) during VT and from 63 mm Hg (range: 58-85) to 15 mm Hg (range: 8-25) during VF. Regardless of the type of underlying cardiac rhythm, transcranial Doppler ultrasonography revealed a constant forward blood flow in the middle cerebral artery during the early phase of induced VT or VF.