Background: Arterial stiffness reduces buffering capacity, exposing the microcirculation to increased pulsatility. Wave reflection could be protective by reducing pulsatility transmitted to low resistance vascular beds such as the brain or the kidney, as suggested by recent data in retinal circulation. Therefore we explored the relationship between wave reflections, arterial stiffness, and renal resistive index.

Methods: We searched our databases of hypertensive patients for subjects who underwent both measurement of arterial stiffness and renal arteries ultrasound. Augmentation index (AIx) and carotid-femoral pulse wave velocity (PWV) as measures of wave reflection and arterial stiffness, respectively, were recorded using the SphygmoCor system. Intraparenchimal renal resistive index (RI), a measure of vascular damage, was obtained in the interlobar arteries by Duplex ultrasound.

Results: Analysis was performed in 175 hypertensive patients (52.9±11.7 yrs), without renal artery stenosis or primary kidney disease. Mean RI was 0.630±0.065, PWV 8.41±1.74 m/s, AIx 26.7±11.5 %. RI was positively associated with AIx (r=0.31, p<0.001) and PWV (r=0.43, p<0.001). Neither AIx nor PWV remained significant predictors of RI in a model including age, gender, body mass index, blood pressure, heart rate, glucose, cholesterol, glomerular filtration rate. Stratifying patients according to tertiles of AIx and PWV, IR was not different between low AIx / high PWV and high AIx / low PWV (0.633±0.062 vs 0.632±0.059, p=ns).

Conclusions: This cross sectional analysis failed to demonstrate an independent relationship between wave reflection and renal resistive index, suggesting that wave reflection could not have a beneficial effect in the renal circulation of hypertensive patients.