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12-03-2012 | Cardiology | Article

One in 50 hypertensive patients develop resistant hypertension within 18 months


Free abstract

MedWire News: One in 50 patients who are newly diagnosed with hypertension go on to develop resistant hypertension within 18 months, research suggests.

The Circulation study also found that patients with resistant hypertension have an increased risk for cardiovascular (CV) events compared with those who have nonresistant hypertension, "supporting the need for greater efforts toward improving hypertension outcomes in this population," say Stacie Daugherty (University of Colorado Denver, Aurora, USA) and co-authors.

They conducted a retrospective cohort study of 205,750 patients with incident hypertension (systolic blood pressure [SBP] ≥140 mmHg or diastolic BP [DBP] ≥90 mmHg) who were started on antihypertensive medications between 2002 and 2006, from the Kaiser Permanente Colorado and Northern California integrated health plans.

All patients were followed for the development of resistant hypertension, which was based on 2008 American Heart Association criteria. According to these, patients were first followed from the time of starting one or more antihypertensive medications to assess whether they were ever on three or more classes of antihypertensive for at least one month during follow up.

They were then divided into groups of controlled and uncontrolled hypertension based on their BP nearest to the date when they started at least three antihypertensives.

Next, the cohort of patients on at least three medications was followed for 1 year to assess hypertension control based on the BP measurement closest to one year after starting three medications, and to assess drug adherence to antihypertensives.

In analysis excluding nonadherent patients (based on a pharmacy refill rate of <80% for all prescribed antihypertensives), 3960 (1.9%) patients - approximately one in 50 - developed resistant hypertension (controlled BP on four or more antihypertensives or uncontrolled BP on three or more antihypertensives at 1 year) a median of 1.5 years from initial treatment. This corresponds to 0.7 cases per 100 years of patient follow up.

These patients were more often male (49.6 vs 44.9%), of White race (60.4 vs 56.8%), older (60.6 vs 58.7 years), and more likely to have baseline diabetes (17.7 vs 9.6%) than those with nonresistant hypertension.

Over a median follow-up period of 3.8 years, CV event rates (nonfatal myocardial infarction, congestive heart failure, stroke, or chronic kidney disease) were significantly higher in patients with resistant than those with nonresistant hypertension (18.0 vs 13.5%; p<0.001).

After adjusting for patient and clinical characteristics, resistant hypertension was associated with a 47% increased risk for CV events.

"These findings are significant as the prevalence of resistant hypertension is expected to increase due to increased life expectancy and the increasing prevalence of factors commonly associated with resistant hypertension such as obesity, diabetes and chronic kidney disease," comment the authors.

However, they say that it is unclear whether the tendency towards worse CV outcomes in patients with resistant hypertension is due to the resistant hypertension status itself or related to blood pressure control. This warrants further study, they add.

In a related editorial, Eduardo Pimenta (Princess Alexandra Hospital, Brisbane, Australia) and David Calhoun (University of Alabama at Birmingham, USA) call the current study "undoubtedly... the most accurate assessment to date of the incidence of resistant hypertension in the United States."

They add: "Overall, these current findings highlight the clinical reality that a growing proportion of patients will need a large number of medications to control their BP."

Daugherty and team conclude that more studies are also needed to assess the prognosis of patients with resistant hypertension in additional community cohorts.

By Piriya Mahendra

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