Doppler-Derived Renal Venous Stasis Index in the Prognosis of Right Heart Failure

Abstract

Background Persistent congestion with deteriorating renal function is an important cause of adverse outcomes in heart failure. We aimed to characterize new approaches to evaluate renal congestion using Doppler ultrasonography. Methods and Results We enrolled 205 patients with suspected or prediagnosed pulmonary hypertension (PH) undergoing right heart catheterization. Patients underwent renal Doppler ultrasonography and assessment of invasive cardiopulmonary hemodynamics, echocardiography, renal function, intra-abdominal pressure, and neurohormones and hydration status. Four spectral Doppler intrarenal venous flow patterns and a novel renal venous stasis index (RVSI) were defined. We evaluated PH-related morbidity using the Cox proportional hazards model for the composite end point of PH progression (hospitalization for worsening PH, lung transplantation, or PH-specific therapy escalation) and all-cause mortality for 1-year after discharge. The prognostic utility of RVSI and intrarenal venous flow patterns was compared using receiver operating characteristic curves. RVSI increased in a graded fashion across increasing severity of intrarenal venous flow patterns (P<0.0001) and was significantly associated with right heart and renal function, intra-abdominal pressure, and neurohormonal and hydration status. During follow-up, the morbidity/mortality end point occurred in 91 patients and was independently predicted by RVSI (RVSI in the third tertile versus referent: hazard ratio: 4.72 [95% CI, 2.10-10.59; P<0.0001]). Receiver operating characteristic curves suggested superiority of RVSI to individual intrarenal venous flow patterns in predicting outcome (areas under the curve: 0.789 and 0.761, respectively; P=0.038). Conclusions We propose RVSI as a conceptually new and integrative Doppler index of renal congestion. RVSI provides additional prognostic information to stratify PH for the propensity to develop right heart failure. Clinical Trial Registration URL: https://www.clinicaltrials.gov/. Unique identifier: NCT03039959.

Keywords: cardiorenal syndromes; intrarenal venous flow patterns; pulmonary hypertension; renal Doppler ultrasonography; venous congestion.

Figures

Figure 1

Congestion stages as defined by intrarenal venous flow patterns. Pulsed‐wave Doppler samples of renal congestion patterns in the interlobar renal vessel. The upward Doppler signal shows the intrarenal arterial flow, which is used to measure renal resistive index; the downward Doppler signal shows the venous flow, used to measure venous impedance index or renal venous stasis index. A, No congestion: continuous venous flow. B, Stage 1 congestion: pulsatile venous flow. C, Stage 2 congestion: biphasic venous flow. D, Stage 3 congestion: monophasic venous flow. D indicates diastole; S, systole; VII, venous impedance index.

Figure 2

Renal venous stasis index (RVSI). The RVSI is a novel Doppler‐based parameter to estimate severity of renal congestion. Pulsed‐wave Doppler samples of renal congestion patterns in the interlobar renal vessel are shown. The upward Doppler signal shows the intrarenal arterial flow, which is used to measure cardiac cycle time; the downward Doppler signal shows the venous flow, used to measure venous flow time. Under physiological conditions, the index is zero due to the presence of a continuous venous flow, whereas it increases with rising severity of congestion. The figure illustrates the method of measurement of RVSI in different congestion stages. ms indicates milliseconds.

Figure 3

Study flow chart. The diagram describes the protocol used for the enrollment of patients in this study.

Figure 4

Association of renal venous stasis index with congestion stages. Under physiological conditions, the renal venous stasis index is zero due to the presence of a continuous venous flow, whereas it increases with rising severity of congestion. Horizontal lines indicate median, boxes indicate interquartile range (IQR), and whiskers indicate minimum and maximum values. Data labels show median (IQR).

Figure 5

RVSI and associated clinical parameters. Severity of renal congestion can be evaluated by measurement of RVSI using renal Doppler ultrasonography. The figure illustrates the associations of RVSI tertiles with RAP and renal function (A), right ventricular systolic function and RA area (B), neurohormonal status (C), and hydration status (D). Fluid overload as measured by bioimpedance is likely to occur because of hemodynamic alterations and neurohormonal activation leading to a deterioration of renal function and fluid retention. BNP indicates B‐type natriuretic peptide; eGFR, estimated glomerular filtration rate (based on Chronic Kidney Disease Epidemiology Collaboration creatinine–cystatin C equation); RA, right atrial; RAP, right atrial pressure; RVSI, renal venous stasis index; TAPSE, tricuspid annular plane systolic excursion; VII, venous impedance index.

Figure 6

Kaplan‐Meier estimate curve according to RVSI tertiles. Patients in the third tertile group had a significantly higher probability than other patients of the composite end point of PH‐related morbidity or death from any cause (P<0.0001). PH indicates pulmonary hypertension; RVSI, renal venous stasis index.