Study examines clinical, kidney morphologic features that predict favorable BP response to renal artery stenting

A retrospective study in the May 2011 issue of the Journal of Vascular Surgery®, the official publication of the Society for Vascular Surgery®, examines clinical and kidney morphologic features that predict a favorable blood pressure (BP) response to renal artery stenting (RAS). Clinicians in the departments of surgery and radiology at the University of Texas Southwestern Medical Center and its affiliated hospitals performed RAS on 149 patients (185 arteries, 36 being bilateral) between January 1, 2000, and July 1, 2008. The median age of the cohort was 68 years and median follow-up was 19 months.

Co-author J. Gregory Modrall, MD, from the department of surgery at the Center explained that patients were categorized as "responders" based on modified American Heart Association guidelines: BP less than 160/90 mm Hg if on fewer antihypertensive medications or a reduction of an average diastolic BP less than 90 mm Hg on the same medications. All other patients were deemed "nonresponders."

Researchers found during a multivariate analysis that three preoperative clinical variables—four or more blood pressure medications, diastolic BP of more than 90 mm Hg and clonidine use may be useful predictors of BP response to RAS, whereas patients with none of these predictors present before stenting are highly unlikely to respond to RAS with improved BP (response rate of 1.5 percent).

A favorable BP response to RAS was observed in 50 of 149 patients. After RAS the 50 responders had a median decrease in systolic BP of 33 mm Hg and a median decrease in diastolic BP of 15 mm. The BP response rate varied significantly based on the number of predictors present per patient. With one predictor, the BP response rate rose to 45 percent; with two or more predictors had at least a 76 percent probability of response.

Renal volume was estimated as kidney length x width x depth/2 based on preoperative computed tomography or magnetic resonance scans. During the study, 86 of the 149 patients had preoperative contrast enhanced computer tomography or magnetic resonance scans to measure parameters of kidney morphology.

"Kidney volume may help in discriminating responders from nonresponders among patient subsets who are marginal candidates for stenting," said Dr. Modrall. He said that among those patients with 3-drug hypertension a larger ipsilateral kidney (volume greater than 50 cm3) increased the BP response rate more than threefold compared with patients with smaller kidneys (63 percent vs. 18 percent BP response rate).

Dr. Modrall added that being cognizant of these predictors of BP response may assist clinicians in patient selection and provide more concrete data with which to counsel patients on the likely outcomes for RAS.