Tight Blood Pressure Control Fails to Stall Kidney Disease in Blacks

By Charles Bankhead ,
BALTIMORE, 29 April 2008 -- Many African Americans getting tight blood pressure control had worsening chronic kidney disease nonetheless, a large multicenter trial found.
During a 10-year follow-up, more than half the patients had deterioration of renal function, progression to end-stage renal disease, or they died, Lawrence J. Appel, M.D., of Johns Hopkins, and colleagues reported in the April 28 issue of Archives of Internal Medicine.
Neither the choice of antihypertensive medication nor a lower blood pressure target affected a patient's likelihood of disease progression.
"These results highlight the importance of preventing initial kidney damage, the critical need to identify modifiable risk factors, and the requirement to test promising therapies at the earliest stages of [chronic kidney disease]," the authors concluded.
The findings came from an extension phase of the African American Study of Kidney Disease and Hypertension (AASK) study. The primary findings of the study were that treatment with an ACE inhibitor reduced the risk of death or progression of kidney disease by 48% compared with a calcium-channel blocker and by 22% compared with a beta-blocker.
Upon completion of the AASK trial, participants were invited to enroll in a cohort study to evaluate the use of therapy targeting the renin-angiotensin system (ACE inhibitors or angiotensin receptor blockers) to treat blood pressure to a target of 130/80 mm Hg. The study involved 1,094 original participants in the AASK trial, all with hypertensive chronic kidney disease. They were followed from 2002 to 2007, and the primary endpoint was the same composite used in the primary trial.
Use of an ACE inhibitor or ARB ranged from 83.7% to 89% during each year of the cohort study, and mean blood pressure during the follow-up study was 133/78 mm Hg.
More than half the patients (567 of 1,094) reached the endpoint during follow-up, resulting in a 10-year cumulative incidence of 53.9%. Among 567 participants with at least seven years of follow-up, 33.5% had a slow decline in kidney function, defined by a mean annual decline in estimated glomerular filtration rate of less than 1 mL/min/1.73 m2.
Acknowledging that the data paint a "sobering picture," the authors emphasized that the findings "do not alter current recommendations for use of [ACE inhibitors or ARBs] and a low blood pressure goal in persons with hypertensive chronic kidney disease. The rate of chronic kidney disease progression would likely have been even greater without renin-angiotensin sysem-blocking therapy."
The authors suggested several strategies to manage modifiable risk factors early in the course of hypertensive kidney disease: nocturnal blood pressure control, aldosterone blockade, combined ACE inhibitor-ARB therapy, fish oil supplementation, bicarbonate therapy, and sodium restriction.
"There are a lot of ideas but none of them has been adequately tested," Dr. Appel said in an interview. "It's hard to say whether there is any blockbuster treatment that is about ready to take off. I don't see one at this point."
In the meantime, clinicians should continue treating patients with hypertensive kidney disease to a low blood pressure target, he added. The means using three or four drugs, if necessary, and frequent blood pressure monitoring in the office or clinic.

Primary source: Archives of Internal MedicineSource reference:Appel LJ, et al "Long-term effects of renin-angiotensin system-blocking therapy and a low blood pressure goal on progression of hypertensive chronic kidney disease in African Americans" Arch Intern Med 2008; 168: 832-839.