Effect of Clopidogrel on Arteriovenous Fistulas for Dialysis—Reply

In Reply: Citing a study by Beathard et al,¹ Drs Wusirika and Rao ask if we misclassified as thrombosed patent fistulas with decreased blood flow due to stenosis. The study by Beathard et al examined fistulas that failed to develop, not fistulas with clinically diagnosed thrombosis. Therefore, the frequency of angiographic stenosis in their study cannot be used to assess accuracy of clinical diagnoses of thrombosis. Nonetheless, we acknowledge our inability to perform angiography to confirm these diagnoses in our trial.² If stenosis does often underlie maturation failure, our finding of a benefit of clopidogrel on patency but not suitability suggests that our thrombosis events were not misclassified stenoses. As we discussed, the disparity between the effects of the intervention on thrombosis and suitability suggests that fistula thrombosis is a manifestation, rather than cause, of maturation failure. We agree that additional study is needed to elucidate the mechanisms underlying maturation failure.