HERCULES Trial Shows Renal Stenting Significantly Reduces Systolic Blood Pressure
May 6, 2011 – A substance secreted by the heart that is associated with congestive heart failure and renal failure is not predictive of reduction in systolic blood pressure in patients treated with renal artery stenting, according to results from the HERCULES trial. Data was presented as a late-breaking clinical trial at the Society for Cardiovascular Angiography and Interventions (SCAI) 2011 Scientific Sessions in Baltimore.
The HERCULES trial is a prospective, multicenter trial of renal stenting in patients who have blockages to their renal arteries, which can worsen hypertension and threaten kidney function. The study reviewed outcomes for 202 patients (241 lesions) with uncontrolled hypertension who were treated with a renal artery stent between August 2007 and October 2009. The primary endpoint was nine-month restenosis rate and the secondary endpoints included changes in blood pressure, anti-hypertensive medications, renal function and the predictive value of brain natriuretic peptide (BNP).
The primary endpoint of the study was met, with a nine-month restenosis rate of 10.5 percent (p<0.0001), which was significantly lower than the performance goal of 28.6 percent. Results for the secondary endpoints showed systolic blood pressure (SBP) decreased significantly after stenting with no change in medication requirements, but mean BNP levels remained elevated after one month. The study found no evidence of a correlation between elevated pre-treatment BNP levels and SBP reduction at follow-up. Researchers measured BNP prior to treatment, at 24 hours and 30 days.
"The clinical results are promising, as we found very low restenosis rates and a significant drop in blood pressure following renal artery stenting," said Michael R. Jaff, D.O., medical director of the Vascular Center at Massachusetts General Hospital in Boston. "One goal of the study was to identify a means to predict which patients will have the best outcome after renal artery stenting. No correlation was found between pre-treatment BNP levels and SBP response, and patients with the best results did not have a significant reduction in BNP levels, so our results show the search must continue for the best means to predict how patients will fare after renal artery stenting."
Researchers hypothesized that BNP could be useful in predicting outcomes in patients with uncontrolled hypertension who are treated with renal artery stenting. BNP is secreted in the heart in response to excessive stretching of the heart muscle cells. Its name was derived from its first discovery in the brain of pigs, but in humans it is produced mainly in the heart. Currently, BNP is useful in diagnosing and monitoring patients with congestive heart failure.
In one small series of patients with hypertension and renal artery blockage, those patients with high BNP levels (>80) had impressive reductions in blood pressure compared to those patients whose baseline BNP levels were not elevated (Silva et al. Circulation 2005;111:328-33). A subsequent larger series of 120 patients suggested that the baseline BNP of >50 was predictive of clinical improvements in blood pressure in 79 percent of patients (Staub D et al. Eur J Vasc Endovasc Surg 2010;40:599-607).
"Because blockages to the kidney arteries can worsen hypertension and damage the kidneys, we wanted to investigate whether high levels of BNP – a substance in the blood that is elevated in patients with congestive heart failure – would change after patients receive a stent to open up and keep open the blockages in the kidney arteries," said Jaff. "This study finds the BNP levels prior to treatment are not predictive of a reduction in blood pressure after treatment."
Nearly one in three Americans suffers from high blood pressure, and as many as a quarter of patients with high blood pressure cannot control it despite the use of multiple medications, according to the National Institutes of Health. Blockages that narrow the blood vessels to the kidneys are one important cause of high blood pressure and may lead to kidney failure. Worldwide, hypertension is believed to cause one out of every eight deaths.
Jaff is a non-compensated consultant for Abbott Vascular and a board member for VIVA Physicians, a 501(c) 3 not-for-profit education and research organization.
For more information: www.scai.org