Survival of low-TF mice with different levels of TFPI. We determined the survival of low-TF mice containing either wild-type levels of TFPI (TFPI^+/+; n = 8), 50% levels of TFPI (TFPI^+/–; n = 36), or no TFPI (TFPI^–/–; n = 21). All 3 groups exhibited a statistically significant difference in survival.