Plasma renin testing provides an effective, practical, and possibly superior way to improve BP control in patients with treated but uncontrolled hypertension, a study found.
This approach is based on that premise that hypertension in patients who have low plasma renin activity (PRA)—less than 0.65 ng/mL/h—is likely caused by too much sodium in the body, while hypertension in those with a PRA of 0.65 ng/mL/h or higher results from excessive renin-angiotensin system (RAS) vasoconstrictor activity.
By knowing patients’ PRA, clinicians can decide which medications are most appropriate for lowering BP. For example, if that a patient’s hypertension is likely due to excessive sodium volume (V patients), they can prescribe medications that address sodium-volume problems, such as diuretics, calcium antagonists, or alpha-1 blockers, and withdraw anti-RAS drugs, such as ACE inhibitors, angiotensin receptor blockers, or beta blockers. The opposite strategy would apply to patients with RAS-dependent hypertension (R patients).
Brent M. Egan, MD, of the Medical University of South Carolina in Charleston, and colleagues studied 77 patients with treated but uncontrolled hypertension. They randomly assigned 38 subjects to receive care as part of a renin test-guided therapeutic (RTGT) algorithm and 39 subjects to receive usual clinical hypertension specialists’ care (CHSC).
In the RTGT group, V patients would receive antivolume drugs and be taken off RAS medications. The investigators applied converse strategies to R patients.
The mean baseline BP was similar in both the RTGT and CHSC groups: 157/87.1 and 153.6/91.9 mm Hg, respectively. At the final visit, BP was controlled in 28 (74%) of the RTGT group vs. 23 (59%) of the CHSC group, the investigators reported in the American Journal of Hypertension (2009;22:792-801). The mean systolic BP (SBP) declined to 127.9 in the RTGT group and 134 in the CHSC group.
The decline within each group was significant, but the difference in SBP between the groups was not. Diastolic BP declined significantly in both the RTGT and CHSC patients (to 73.1 and 79.8 mm Hg, respectively), and the difference between the groups was significant. The decline in SBP from baseline to the final visit was significantly greater in RTGT patients compared with the CHSC group (29.1 vs. 19.2).
Overall, the mean number of antihypertensive medications that patients took did not change significantly within and between the study arms. Compared with CHSC patients, however, the mean number of antihypertensive medications declined by 0.5 in the V patients and rose by 0.7 in the R patients, a significant difference between the groups, according to the researchers.
The authors noted that their results indicate that clinical hypertension specialists’ referral and renin test-guided therapy are both effective pathways for improving BP control in treated, uncontrolled hypertension. Although referral to a hypertension specialist can improve BP control, they added, the number of such specialists is “quite insufficient” to manage the nation’s estimated 17 million treated but uncontrolled hypertensive patients.
“Accordingly, the RTGT algorithm emerges as a practical and objective biochemical alternative to CHSC that can be used in most clinical settings by a wide range of health-care providers for addressing the public health burden of treated and uncontrolled hypertension,” the authors wrote.