To the Editor: We thank Dr. Zhao and colleagues for their thoughts regarding our recent publication.1 The use of arteriovenous fistula (AVF) for treatment resistant hypertension in patients without chronic kidney disease (CKD) has been investigated prospectively in small trials. On the other hand, the concept of a prospective trial in the CKD population would be a paradigm shift in regards the use of AVF prior to hemodialysis initiation. Recent reports of slowing of renal function decline in advanced CKD suggest that an AVF may not simply be a means to the ultimate therapy: hemodialysis, but rather the therapy itself in CKD.2,3 Our report does not immediately support this notion given the modest reductions, if any, in systolic blood pressure, and a greater effect on diastolic blood pressure. Dr. Zhao and colleagues highlight important variables that contribute to blood pressure in CKD patients as compared to non-CKD patients including vascular calcification and sodium water handling, which may not be directly affected by AVF. In addition, we acknowledge that unavailable hemodynamics variables in regarding to successful AVF creation limit our ability to fully assess the effect of a functional AVF on blood pressure in CKD patients; and the use of an AVF at the start of hemodialysis may not be an adequate surrogate for these hemodynamic parameters.
It is possible that the effect of AVF on blood pressure seen in non-CKD patients may have been primarily a placebo effect. Adequately designed trials of AVF creation in non-CKD patients with true placebo (catheterization without AVF creation) have not been conducted. In pre-dialysis patients, the anticipation (or fear) of dialysis initiation with AVF creation may eliminate any therapeutic effect of the simply having the surgery for AVF creation.
In regards the issue of timing of fistula creation to dialysis initiation, we agree that most patients do not have a fistula created 12 months prior to dialysis initiation. Our patient flow diagram demonstrates that significant drop off in numbers of patients with an AVF when the 12-month time frame was applied. The time frame was important to ensure isolation of the effects of the fistula from the dialysis therapy.
If a prospective study were to be conducted, selecting a population in which a differential effect on systolic and diastolic blood pressure would be minimized will be important, given the adverse effects of low diastolic blood pressure on outcomes.4 Ultimately we agree with the authors that the evidence is mounting for the analysis of the AVF as more than a means to access the blood space for hemodialysis. We hope that our report will help to spur a greater interest in this line of questioning as the need to manage the cardiovascular outcomes of advanced CKD as well as minimizing the numbers of patients requiring renal replacement therapy is great.
DISCLOSURE
The author(s) declared no conflict of interest.
REFERENCES
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