Investigators led by Oliver Dörr, MD, of the University of Giessen (Giessen, Germany), measured kidney function at baseline and multiple time points post procedure in 62 consecutive patients with drug-resistant hypertension undergoing renal denervation at 2 centers from September 2011 through March 2012. The cohort included 8 patients (13%) with impaired renal function, defined as an eGFR less than 45 mL/min/1.73 m².

Multiple Biomarkers Assess Kidney Function

Results of standard metrics of renal function including serum creatinine, eGFR, and blood urea nitrogen (BUN) as well as 2 highly sensitive biomarkers of early kidney damage, urinary neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule (KIM)-1, showed no significant declines at 24 or 48 hours or at 3-month follow-up (table 1).

Table 1. Change in Kidney Function, Baseline to 3 Months

In particular, patients with impaired renal function at baseline did not display alterations in NGAL or KIM-1 levels at either the early time points or at 3 months.

In terms of efficacy, 88.7% of patients achieved significant blood pressure reduction at 3 months (table 2).

Table 2. Median Change in Blood Pressure, Baseline to 3 Months

No difference in kidney function was observed regardless of the outcome of renal denervation.

The authors say preserved renal function after denervation “may indicate that the autoregulatory mechanisms of the kidneys are not disturbed by this interventional procedure. In particular, the [renal sympathetic denervation]-related reduction in efferent sympathetic activity leads to decreased renin release, and the effect on the afferent sympathetic fibers results in modulation of the peripheral vascular tone and reduction in renal blood flow.”

Dr. Dörr and colleagues conclude, “Our results provide additional evidence that [renal sympathetic denervation] in patients with resistant [hypertension] is safe and potentially could be used for patients with progressive chronic kidney disease.”

Contrast Material Accused—and Acquitted

In a telephone interview with TCTMD, George L. Bakris, MD, of the University of Chicago Medical Center (Chicago, IL), argued that although some consider sympathetic denervation itself the source of potential kidney damage, the more likely suspect is the contrast material used during the procedure.

“I consider [this study] basically a variant model for contrast nephropathy,” he said, adding that “the [biomarker] to focus on is KIM-1, because it is very sensitive and far more specific than NGAL—although neither was dramatically affected.

“These are preliminary data suggesting that from the standpoint of acute kidney injury, this procedure is relatively safe if done properly and should not be a major concern,” Dr. Bakris continued. He cautioned, however, that the results were obtained “under a best-case scenario,” with the procedure performed by very experienced operators using an appropriate hydration protocol and thus should not be generalized.

In fact, the percentage of patients with baseline kidney impairment is probably much higher than the 13% seen in this study, he noted, and since this population is excluded from Symplicity HTN-3, the pivotal US trial, “it’s good that it has been captured in this study, in what I would call a nested cohort, to show that this group is behaving like the general group [of renal denervation candidates].” A separate evaluation of the impaired cohort would have been helpful, he noted, although the small number of such patients in this study would have rendered any findings underpowered.

In an e-mail communication with TCTMD, Deepak L. Bhatt, MD, MPH, of Brigham and Women’s Hospital (Boston, MA), observed that the potential impact of both denervation and contrast material on kidney function has been an ongoing concern.

“I think it is very reassuring that no renal damage was seen with these sensitive biomarkers,” he wrote. “It does not appear that renal artery denervation harms the kidneys. Indeed, elsewhere in the world it is being studied to see if it helps prevent decline in renal function. Of course, one always needs to be cautious about contrast use in patients with low GFRs,” he added.

Study Details

On average, each patient was administered 78.5 ± 39.0 mL of contrast fluid. All patients received 500 mL 0.9% NaCl intravenously before and after the procedure, which was performed bilaterally in a single session using a 6-Fr sheath via a femoral artery.

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