**5. Conclusion**

A beneficial effect of hemodiafiltration on arterial stiffness is supported by another observa‐ tional study, in which aortic PWV measurements were performed 6 months apart in three different groups of ESRD patients [38]. The first group consisted of 69 ESRD patients receiving conventional low-flux hemodialysis, the second group consisted of 78 ESRD patients who were switched from low-flux hemodialysis to on-line hemodiafiltration, and the third group included 142 ESRD patients receiving long-term renal replacement therapy with on-line hemodiafiltration. Over the 6-month observational period, a significant increase in aortic PWV was noted in those patients treated with hemodialysis (9.5 ± 1.9 versus 10.2 ± 2.2 m/s, p < 0.01) as well as in those switched from hemodialysis to hemodiafiltration (9.4 ± 1.9 versus 10.1 ± 2.2 m/s, p < 0.01); in contrast, aortic PWV remained unchanged in the group of hemodiafiltration (9.9 ± 2.1 versus 10.1 ± 2.2 m/s) [38]. The most important finding of this study was that aortic PWV remained constant during follow-up only in those patients receiving long-term treatment with hemodiafiltration, whereas aortic PWV increased in patients who were switched from hemodialysis to hemodiafiltration. This observation could be interpreted in two different ways: either the 6-month-long therapy with hemodiafiltration might be inadequate in order to modify the arterial wall structure and stiffness, or aortic PWV increased in those patients switched to hemodiafiltration due to a carry-on effect of previous long-term therapy with

The above beneficial impact of hemodiafiltration in causing regression of arterial stiffness was not confirmed in a recent subanalysis of 189 prevalent dialysis patients participating in the CONvective TRAnsport STudy (CONTRAST) trial [39]. In this study, ESRD patients receiving conventional low-flux hemodialysis were randomly assigned in a 1:1 ratio for treatment with on-line hemodiafiltration or continuation of low-flux hemodialysis for a mean follow-up period of 36 months. Median aortic PWV at baseline was 9.8 m/s (interquartile range: 7.5–12.0 m/s). Aortic PWV was not significantly changed over time, and the annual rate of PWV change had no difference between the on-line hemodiafiltration and hemodialysis groups (hemodia‐ filtration group: −0.01 m/s/year, 95% CIs: −0.41 to 0.40 m/s/year; hemodialysis group: −0.04 m/ s/year, 95% CI: −0.31 to 0.23 m/s/year; p value for the between-group comparison: 0.89) [39]. The absence of difference between the two dialytic modalities in the rate of PWV change was consistent across subgroups of age, sex, residual renal function, dialysis vintage, diabetes, and history of pre-existing cardiovascular disease. Of note, the annual rate of PWV change had once again no difference between the two dialytic modalities regardless of the convection volume used for on-line hemodiafiltration (convection volume <18.9 L/session: 0.37 m/s/year; 95% CIs: −0.25 to 0.98 m/s/year, p = 0.23; convection volume >18.9 L/session: −0.01 m/s/year;

**4. Studies comparing the effect of hemodiafiltration versus hemodialysis**

The above contradictory results of clinical studies that evaluated the comparative effectiveness of hemodialfiltration versus standard hemodialysis in causing regression of arterial stiffness

conventional hemodialysis.

52 Advances in Hemodiafiltration

95% CIs: −0.59 to 0.57, p = 0.99) [39].

**on mortality**

In summary, the currently available evidence from observational and randomized clinical studies does not conclusively support a clear superiority of hemodiafiltration versus standard hemodialysis in improving arterial compliance. The contradictory results of clinical studies with respect to PWV, a surrogate cardiovascular risk factor, are in line with the uncertain survival benefit of convective dialytic modalities in large-scaled clinical trials evaluating "hard" cardiovascular outcomes. Additional research efforts are urgently warranted to fully elucidate the comparative effectiveness of hemodiafiltration versus conventional hemodialysis on arterial stiffness attenuation. In the meantime, we believe that dialysis treatment optimi‐ zation is undoubtedly one useful tool toward cardiovascular risk reduction for patients receiving maintenance hemodialysis.

## **Author details**

Panagiotis I. Georgianos1 , Evangelia Dounousi2 , Theodoros Eleftheriadis1 and Vassilios Liakopoulos1\*

\*Address all correspondence to: liakopul@otenet.gr

1 Division of Nephrology and Hypertension, 1st Department of Internal Medicine, AHEPA Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece

2 Department of Nephrology, Medical School, University of Ioannina, Ioannina, Greece
