Cerebrovascular Accidents with Tetralogy of Fallot

Introduction  Cerebrovascular accidents (CVA's) represent a dangerous complication for cyanotic children with tetralogy of Fallot. This complication has been related to the increased hematocrit found in cyanotic patients with extremely low arterial oxygen saturations.^1,2 A hematocrit level of 70% has been considered as the limit above which cerebrovascular accidents occur with increased frequency.^3,4 Various authors have stated that factors other than hematocrit level, such as degree of anoxia or polycythemia, may play a more important role.^3,5We noticed in surveying our patients with cyanotic tetralogy of Fallot that cerebrovascular accidents occurred only in the group under 5 years of age. These central nervous system complications did not occur in those with high hematocrits and hemoglobin levels, but were found in those with the highest red blood cell counts. This dissociation between normal or only slightly elevated hematocrit levels and greatly elevated red blood cell counts suggested a