Source: MetroHealth System

The inconclusive findings of the HERCULES trial, published in the September issue of Catheterization and Cardiovascular Interventions, have encouraged researchers to continue investigations to see if renal artery stenting is safe and effective in patients with uncontrolled hypertension (HTN) and atherosclerotic renal artery stenosis (ARAS).

The HERCULES trial, which was presented by Michael R. Jaff, DO, at SCAI.11 in Baltimore, demonstrated that patients with the most severe hypertension (HTN) before renal artery stent deployment benefited from a reduction in blood pressure not experienced with medical therapy, regardless of the number of agents used.

Despite some positive results in HERCULES, the “disappointing finding” was “the absence of evidence of a predictive value for BNP [brain natriuretic peptide] levels,” Jaff et al wrote.

The trial was the the largest prospective series to evaluate the predictive role of BNP in patients with ARAS and HTN; however, it was still a single-arm trial. The results demonstrated that neither the preprocedure BNP values nor the change in BNP values predicted the clinical benefit of renal artery stent deployment on blood pressure reduction. 

Although the trial was not designed or powered to define clinical predictors of blood pressure response, the nonlinear relationship between baseline systolic BP and percent systolic BP improvement suggests that patients with higher baseline systolic BP may benefit most from the procedure, the study authors noted.

“The quest for a clinical, imaging or laboratory biomarker of blood pressure response from renal artery stent deployment remains elusive, given the absence of predictive value of BNP,” Jaff et al concluded. “Further studies for predictors of clinical response following percutaneous renal revascularization are needed.”

In the accompanying editorial, William B. Hillegass, MD, MPH, from the Center for Outcomes and Effectiveness Research and Education at the University of Alabama at Birmingham in Birmingham, Ala., questioned the utility of an observational trial with no randomized control group.

Answering his own question, he wrote that "the search for defining characteristics that may predict benefit. "In Jaff et al.’s study, BNP levels decreased after renal artery stenting, but preprocedural BNP failed to predict hypertension benefit.” 

Despite the challenges of gathering data from such a trial, Hillegass concluded: “Until a practical and ethical randomized strategy tests renal artery stenosis in on-target patients with high a priori likelihood of benefit, observational data such as the HERCULES trial … should not be totally discounted in assessing the efficacy of renal artery stenting,” he wrote.