VKORC1 and heart failure: Furthermore, VKORC1 c.−1639G > A and CYP2C9*2 and *3 were found to be the major genetic variants to predict warfarin dosage in a Qatari patient cohort, explaining 39.2% of warfarin dose variability, along with hypertension, smoking and heart failure, while CYP4F2*3 was not associated with warfarin dose48.