For patients with hypertension, ambulatory blood pressure monitoring has been recommended as the preferred method for diagnosing hypertension because it gives physicians an expanded picture of the patient’s blood pressure over a 24-hour period rather than a single snapshot in the office.
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Researchers found a high prevalence of treatment-resistant hypertension in chronic kidney disease (CKD), and very few patients with so-called “white coat hypertension,” in which their blood pressure was high in a clinical setting, but returned to acceptable levels after they went home. Hypertension is considered treatment-resistant when blood pressure can’t be brought under control even when the patient is on three different medications at the highest dose they can tolerate. Alternately, if blood pressure is under control but the patient requires four or more medications to manage it, it’s also considered treatment-resistant.
“The current analysis is the largest cohort of patients with CKD in which the prevalence and prognostic significance of resistant hypertension is being studied utilizing both office blood pressure measurement and ambulatory blood pressure monitoring,” says George Thomas, MD, Director of the Center for Blood Pressure Disorders in Cleveland Clinic’s Glickman Urological & Kidney Institute and co-author on the study, which was presented in November at a meeting of the American Society of Nephrology in Washington, D.C.
Building on previous research
The research expands on an earlier study in which Dr. Thomas and a group of researchers looked at treatment-resistant hypertension in patients with CKD. Both studies used data from the Chronic Renal Insufficiency Cohort (CRIC) study, which followed a national cohort of about 4,000 patients with CKD for five years.
In the group’s previous study, the researchers found that the prevalence of treatment-resistant hypertension was high in patients with CKD. They also found that patients with treatment-resistant hypertension were at greater risk of a cardiovascular event like heart attack, stroke or heart failure, as well as poor kidney outcomes like a more-than-50% decline in kidney function or end-stage renal failure requiring dialysis (Thomas et al. Prevalence and Prognostic Significance of Apparent Treatment Resistant Hypertension in Chronic Kidney Disease: Report from the Chronic Renal Insufficiency Cohort Study. Hypertension, 2016 Feb; 67 (2): 387-396)
A closer look at ambulatory blood pressure monitoring
That analysis used office-based blood pressure measurements only. For the current follow-up study, Dr. Thomas and his team wanted to take a closer look at the data to determine if using ambulatory blood pressure monitoring would provide additional information. They looked at patients who had undergone both office-based and ambulatory blood pressure monitoring, and compared the results.
Once again, they found that there was a high prevalence of treatment-resistant hypertension in CKD patients, with 34% showing uncontrolled resistant hypertension and 57% needing more than three medications to keep their blood pressure under control. “The event rates of adverse cardiovascular and kidney outcomes and death were higher in these groups compared to those with no resistant hypertension, indicating that treatment resistant hypertension confirmed by ambulatory blood pressure monitoring identifies those at high risk for adverse events,” says Dr. Thomas.
But they also found low rates of white-coat hypertension. Only 8% of patients in the group had a lower blood pressure level with ambulatory monitoring compared to those that were recorded in a clinical setting. “Our results would suggest that if CKD patients have high blood pressure in the office, the chances are good that their ambulatory blood pressure is also high,” notes Dr. Thomas. “Not all clinicians may have the ability to monitor CKD patients with ambulatory blood pressure monitoring, and when that’s the case the office measurement should be taken seriously; it shouldn’t be ignored.”
Overall, Dr. Thomas says the study reaffirms that ambulatory blood pressure monitoring is a better option when it’s possible. “Patients who have treatment-resistant hypertension should be monitored more closely,” he says. “Our results suggest they’re at higher risk for poorer outcomes.”