#1819 The role of renal functional reserve in eGFR decline over 2 years in hypertensives and normotensives with preserved renal function

Abstract Background and Aims Renal Functional Reserve (RFR) has been considered as a promising tool for the diagnosis of early nephron loss and functional renal mass. We aimed to assess whether RFR plays a role in the change of eGFR over time in normotensive and hypertensive patients with preserved renal function and also to examine any correlation of RFR with hemodynamic load, inotropic response and target organ damage. Method In a 24-month prospective study, newly diagnosed essential hypertensives and normotensives with eGFR≥60 ml/min/1.73 m2 were included. The following parameters were measured at baseline: RFR (determined by endogenous creatinine clearance after an acute oral protein load), office blood pressure (BP), 24h ambulatory BP profile, treadmill stress test, and echocardiographic examination. Serum creatinine measurements were also measured at months 12 and 24. Results A total of 51 hypertensives and 20 normotensives completed the study (mean age 53.2 ± 12.1 and 54.3 ± 10.0 years, respectively). Non-significant differences were found between these two groups regarding RFR levels (25.1 ± 18.7 vs 27.7 ± 15.7 ml/min, P = 0.6), annual change (Delta(12–0)m) of eGFR (0.04 ± 1.8 vs −0.75±0.9 ml/min/1.73 m2, P = 0.06) and two-year change (Delta(24–0)m) of eGFR (−0.70 ± 2.3 vs −1.1 ± 1.1 ml/min/1.73 m2, P = 0.46). Hypertensives with RFR≥30ml/min showed a smaller change in the Delta(24–0)m eGFR compared to those with RFR<30ml/min (0.5 ± 2.6 vs −1.4 ± 1.7 ml/min/1.73 m2, P = 0.002). Similarly, the Delta(24-0)m eGFR was significantly lower in normotensives with RFR ≥30ml/min compared to normotensives with RFR <30 ml/min (−0.6 ± 1.3 vs -1.6±0.7 ml/min/1.73 m2, P = 0.02). A dipping pattern of 24 h-SBP was significantly more frequent in hypertensives with high RFR (64.4 vs. 34.4%, P < 0.05). Moreover, patients with lower RFR values showed a blunted heart rate response to exercise during treadmill test (r = 0.29, P < 0.05). None of the echocardiographic parameters differed between the groups of hypertensives. Conclusion RFR did not differ between hypertensive and normotensive subjects with preserved renal function. However, normotensives and hypertensives with RFR≥30ml/min showed a less pronounced change in eGFR at 2 years than those with RFR <30ml/min. Finally, in hypertensive patients with preserved GFR, reduced RFR was related to non-dipping BP phenotype as well as to attenuated exercise HR response.