#2919 Renal functional reserve assessment in patients with coronary microvascular dysfunction and preserved renal function—experience of a center
Authors: Bora Margarita , Alexakou Zoe , Sakalidis Athanasios , Kourniotis Dimitrios , Stambolliu Emelina , Stathopoulou Elpiniki , Chalkia Aglaia , Kapota Athanasia , Giannou Panagiota , Dimitriadis Kyriakos , Tsioufis Konstantinos , Petras Dimitrios 
Published: May 2024

Abstract

Background and Aims
Renal Functional Reserve (RFR) is a field of scientific debate and may be a valuable diagnostic tool for the early detection of subclinical renal disease. According to literature, chronic kidney disease is related to cardiovascular disease (CVD), however the available data on the association of early renal dysfunction and CVD are sparse. The aim of the present study is to evaluate RFR in patients with coronary microvascular dysfunction (CMD) and preserved renal function [eGFR≥ 60 ml/min/1.73 m2 (CKD-EPI) and proteinuria&lt; 400 mg/24 h].

Method
This is a single-center, prospective study enrolling patients with INOCA. We are presenting preliminary results. In the absence of significant coronary artery stenosis, functional coronary circulation assessment was performed for all patients and we estimated coronary flow reserve (CFR) and index of microvascular resistance (IMR). In all participants, RFR was estimated by endogenous creatinine clearance after oral protein load (cooked meal, 1.2 gr/kg). Normal RFR was defined as ≥30 ml/min/1.73 m2. Also, patients with INOCA were offered 24-hour Ambulatory Blood Pressure Monitoring (ABPM).

Results
A total of 22 participants have been enrolled so far in study: 10 without CMD—control group [7 female, mean age: 54.4 ± 8.1 years) and 12 with INOCA—CMD group (9 female, 75%, mean age: 53.5 ± 10.3 years). CMD patients were classified into 2 groups, structural and functional endotype (CFR&lt;2.5 and an IMR≥25 were considered abnormal). The RFR value for CMD group is 7.4 ± 6.3 ml/min/1.73 m2, while for non-CMD group 36.3 ± 5.8 ml/min/1.73 m2 (p &lt; 0.005), relationship that remained statistically significant after controlling for confounding factors. Regarding the two endotypes of MVD, it was found that RFR for the patients with the functional endotype is 3.5 ± 2.4 ml/min/1.73 m2, while for those with the structural endotype 9.3 ± 6.9 ml/min/1.73 m2 (p-value = 0.061). Furthermore, no statistically significant relationship emerged between RFR and IMR, CFR indices (p = 0.347, p = 0.263). According to data from 24 hr ABPM, there were no significant differences in ambulatory blood pressure (systolic and diastolic) between the two endotypes of CMD (p = 0.594, p = 0.243), as well as no relationship with RFR (p = 0.553, p = 0.594). However, the proportion of non-dippers (for both SBP and DBP) was significantly higher in functional CMD endotype (p &lt; 0.05). It was not found correlation between RFR and non-dipping phenotype, both for SBP and DBP (p = 0.561, p = 0.238).

Conclusion
Abnormal RFR has been observed in all patients with microvascular dysfunction. In addition, patients with functional CMD show a lower RFR value compared to those with structural. RFR is not related to blood pressure or the non-dipping pattern. Given the hypothesis that the assessment of renal functional reserve is an early diagnostic tool for subclinical renal disease, the early identification of patients with specific phenotypes—such as INOCA and pathological RFR—could contribute to the individualization of therapeutic interventions.