Impact of Renal Function Trajectory on Renal Replacement Therapy and Mortality Risk after Renal Artery Revascularization
What is the impact of renal function trajectory, defined as the change in renal function over time before and after renal artery stent placement, on long-term risk for renal replacement therapy (RRT) and mortality?
Post intervention eGFR trajectory improvement approaching 40 mL/min/1.73 m2 was associated with decreased RRT and mortality risk, indicating that patients with advanced CKD and renal artery stenosis may benefit from revascularization.
Takahashi, Edwin A. et al. Impact of Renal Function Trajectory on Renal Replacement Therapy and Mortality Risk after Renal Artery Revascularization. Journal of Vascular and Interventional Radiology, Volume 31, Issue 4, 592 – 597.
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Figure 1. Kaplan–Meier estimates for freedom from the need for RRT after renal artery stent placement. Fourteen patients were started on RRT, 16 died, and 9 were lost to follow-up within 1 year of intervention, resulting in an initial number at risk of 359 patients.
Evidence in support of aggressive diagnosis and revascularization of renal artery stenosis is evolving. Data on renal function trajectory is lacking. The authors of this study evaluated the effect of renal artery stenting on renal replacement therapy (RRT)-including hemodialysis and transplantation-in addition to all-cause mortality based on renal function change from 6-12 months before intervention to the time of intervention and from the time to intervention to 6-12 months after intervention.
Retrospective review of 398 patients who underwent renal artery stenting was performed. Renal artery stent placement was performed if Doppler US showed a main renal artery peak systolic velocity >180 cm/s or a renal-to-aortic radio >3.5. Angiographically, stenoses greater than or equal to 50% were treated with angioplasty followed by balloon-expandable bare-metal stent placement without distal embolic protection. Bilateral renal artery stenosis was treated in 162 patients (41%). Primary outcome was impact of estimated glomerular filtration rate (eGFR) on the incidence of RRT and mortality. Potential contributing factors to RRT such as medications, 24-hour proteinuria, presence of CKD, coronary artery disease, diabetes, and smoking were analyzed.
Of the 398 patients, 14 started RRT, 16 died, and 9 were lost to follow-up within 1 year of the procedure. The RRT-free survival rate at 5 years was 92.1% (95% CI, 88.0%–96.1%). 248 patients died after 6–12-month post-intervention (5 year mortality risk of 60.3%). Mean pre-interventional, time-of-intervention, and post-interventional eGFR measurements were 48.3 mL/min/1.73m2±18.7, 42.5 mL/min/1.73 m2±17.8, and 45.5 mL/min/1.73 m2±20.1, respectively. The eGFR trajectory from 6–12 months before intervention to the time of intervention was not significantly associated with risk for RRT or all-cause mortality (P=.47 and P=.45, respectively). However, the eGFR trajectory from intervention to 6–12 months after intervention was significantly associated with freedom from RRT (P=.02). This change was not associated with freedom from all-cause mortality (P=.21). Among patients with a post-interventional eGF<40 mL/min/1.73 m2, for a 1-unit eGFR increase up to 40 mL/min/1.73 m2, there was a significant decrease in RRT risk (HR, 0.87; 95% CI, 0.83–0.91; P<.001) as well as all-cause mortality risk (HR,0.95; 95% CI, 0.94–0.97; P<.001). However, patients with an eGFR>40 mL/min/1.73 m2 at 6–12 months after intervention did not experience lower incidences of RRT or death. Higher rates of RRT were seen with diabetes at the time of intervention, increased baseline proteinuria, and stage 4/5 CKD. On univariate analysis, higher mortality rates were seen in patients with diabetes, increased baseline proteinuria, and stage 4 CKD. On multivariate analysis, higher mortality was seen with diabetes was the only comorbidity associated with increased mortality.
Following the CORAL trial, it is encouraging to see data which may support a greater role for renal artery stenting for renovascular hypertension. The main finding of this study is that eGFR less than or equal to 40 mL/min/1.73 m2 after intervention has a beneficial effect on RRT and mortality. However, this study does have limitations in that the criteria for and severity of hypertension and renal dysfunction were not described and that hemodynamic significance of renal artery lesions were determined by a threshold of 50% or more stenosis on angiography, without pressure measurements. Dr. Sos discusses these limitations and others in a thorough commentary. More work on renal artery stenting in the form of large, prospective, randomized trials are necessary.
Zagum Bhatti, MD
Department of Radiology, Interventional Radiology Division
University of Texas Health Science Center at Houston, Houston, TX