Renal resistive index and cardiovascular and renal outcomes in essential hypertension

Increased renal restive index (RI) measured using Doppler ultrasonography has been shown to correlate with the degree of renal impairment in hypertensive patients. We investigated the prognostic role of RI in cardiovascular and renal outcomes. A total of 426 essential hypertensive subjects (mean age, 63 years; 50% female) with no previous cardiovascular disease were included in this study. Renal segmental arterial RI was measured by duplex Doppler ultrasonography. During follow-up (mean, 3.1 years), 57 participants developed the primary composite end points including cardiovascular and renal outcomes. In multivariate Cox regression analysis, RI was an independent predictor of worse outcome in total subjects (hazard ratio, 1.71 for 1 SD increase), as well as in patients with estimated glomerular filtration rate (eGFR) <60 mL/min per 1.73 m(2) (hazard ratio, 2.11 for 1 SD increase; P<0.01, respectively). When divided into 4 groups based on the respective sex-specific median levels of RI in the eGFR ≥60 and eGFR <60 mL/min per 1.73 m(2) groups, the group with eGFR <60 and high RI (male ≥0.73, female ≥0.72) had a significantly poorer event-free survival rate (χ(2)=126.4; P<0.01), and the adjusted hazard ratio by multivariate Cox regression analysis was 9.58 (95% CI, 3.26-32.89; P<0.01). In conclusion, impairment of renal hemodynamics evaluated by increased RI is associated with an increased risk of primary composite end points, and the combination of high RI and low eGFR is a powerful predictor of these diseases in essential hypertension. In hypertensive patients with chronic kidney disease, RI evaluation may complement predictors of cardiovascular and renal outcomes.