ABCB1 and atrial fibrillation: On the contrary, our study showed that AF patients with the presence of the AA genotype for polymorphism rs2032582 in the ABCB1 gene had higher level of plasma concentration of apixaban than with heterozygote CA genotype (111.9 ± 48.2 ng/mL vs. 91.5 ± 41.7 ng/mL, p = 0.09).