Background: The cardio-renal interaction occurs via hemodynamic and humoral factors. Non-invasive assessment of renal hemodynamics is currently possible by assessment of renal resistive index (RRI) derived from intrarenal Doppler arterial waveforms. So far, only limited information is available regarding the relationship between RRI and cardiac hemodynamics in the general population. We investigated these associations in randomly recruited subjects from a Flemish population.

Methods: In 171 participants (48.5% women; mean age, 52.2 years), using conventional pulsed wave Doppler, we measured RRI (mean, 0.60) and left ventricular outflow tract (LVOT) and transmitral (E and A) blood flow peak velocities and its velocity time integrals (VTI). Using carotid applanation tonometry, we measured central pulse pressure (cPP) and arterial stiffness indexes such as augmentation pressure and carotid-femoral pulse wave velocity.

Result: In stepwise regression analysis, RRI independently and significantly increased with female sex, age, body weight, brachial pulse pressure and use of β-blockers, whereas it decreased with body height and mean arterial pressure. In multivariable-adjusted models with cPP and arterial stiffness indexes as the explanatory variables, we observed a significant and positive correlation of RRI only with cPP (P<0.0001). Among the Doppler indexes of left ventricular blood flow, RRI was significantly and positively associated with LVOT and E peak velocities (P≤0.012) and VTIs (P≤0.010).

Conclusions: We demonstrated that in unselected subjects RRI was significantly associated with cPP and left ventricular systolic and diastolic Doppler blood flow indexes. Our findings imply that in addition to the anthropometric characteristics, cardiac hemodynamic factors influence the intrarenal arterial Doppler waveform patterns.