Significant Correlation between Brachial Pulse Pressure Index and Renal Resistive Index

Background: The renal resistive index (RI) is calculated as (peak systolic velocity - minimum diastolic velocity)/ peak systolic velocity, and has been significantly associated with renal function. Pulse pressure index (PPI) is derived from a formula similar to renal RI, i.e. (systolic blood pressure - diastolic blood pressure)/systolic blood pressure. The purpose of this study was to investigate whether brachial PPI had a significant correlation with renal RI and could be used in identifying patients with impaired renal function. Methods: We consecutively enrolled 255 patients referred for echocardiographic examination. The renal RI was measured from Doppler ultrasonography and blood pressure was measured from an ABI-form device. Results: Patients with brachial PPI >= 0.428 (mean value of brachial PPI) had a lower estimated glomerular filtration rate (eGFR) than those with brachial PPI <0.428 (p < 0.001). After the multivariate analysis was completed, brachial PPI had a significant correlation with renal RI (unstandardized coefficient beta = 0.53, p < 0.001). The areas under the curve for brachial PPI and renal RI in prediction of eGFR < 45 mL/min/1.73 m(2) were 0.682 and 0.893 (both p < 0.001), respectively. Conclusions: Brachial PPI was significantly correlated with renal RI. Patients with higher brachial PPI had a more reduced renal function. Hence, brachial PPI may be able to quickly reflect the intrarenal vascular hemodynamics, and may serve as an important tool for screening and follow-up for patients with abnormal renovascular resistance.