VKORC1 and atrial fibrillation: In addition, findings from the ENGAGE AF-TIMI 48 trial showed that patients carrying warfarin-sensitive (carriers of CYP2C9∗1∗1 + VKORC1-1639A/A or CYP2C9∗1∗3 + VKORC1-1639G/A) or highly sensitive (carriers of CYP2C9∗1∗3 + VKORC1-1639A/A, CYP2C9∗3∗3 + VKORC1-1639A/A, CYP2C9∗3∗3 + VKORC1-1639G/A, or CYP2C9∗3∗3 + VKORC1-1639G/G) genotype functional bins of CYP2C9 and VKORC1 spend more time over-anticoagulated and have higher rates of bleeding events than noncarriers during warfarin treatment, especially in the early period after the start of treatment [29].