Office BP not prognostic for resistant hypertension

Medical Tribune January 2009 P16
David Brill

Office-based blood pressure (BP) measurements offer “no prognostic value” for patients with resistant hypertension, a recent study has concluded.


Ambulatory BPs – both systolic and diastolic – were predictors of future cardiovascular morbidity and mortality whereas neither measurement was a significant indicator when recorded in the office, the researchers found.

The study, which followed up 556 outpatients for a median of 4.8 years, also showed that nighttime ambulatory BP was superior to daytime as a prognostic indicator, suggesting that these time periods should be analyzed seperately to give the best assessment of a patient’s cardiovascular risk.

It is only the second prospective study to assess the different BP monitoring strategies in resistant hypertensive patients, according to the researchers, who are based at the Federal University of Rio de Janeiro, Brazil. They note that the superiority of ambulatory BP “is not generally accepted,” despite several studies showing that it offers better cardiovascular risk prediction than office BP in various other patient populations. [Arch Intern Med 2008 Nov 24;168(21):2340-6]

Dr. Chai Ping, a Singapore-based specialist, said that the study should encourage physicians to use ambulatory BP more often for patients with resistant hypertension.

“In the initial evaluation of a patient with elevated office BP despite three or more medications, ambulatory BP monitoring should be performed to confirm that the BP is truly elevated and not a ‘white-coat’ effect,” he said.

“This paper also tells us that suboptimal BP control, as has been known for more than 4 decades now, confers a worse prognosis for hypertensive patients, so every effort must be made to control BP to the targets as recommended by current clinical practice guidelines,” added Chai, who is clinical director of the noninvasive cardiac laboratory at the National University Heart Centre Singapore (NUHCS).

The patients included in the study met standard criteria for resistant hypertension. The mean hypertension duration at enrollment was 18 years. Some patients were followed up for as long as 9 years.

A total of 109 patients (19.6 percent) reached the study’s primary endpoint – a composite of fatal and non-fatal cardiovascular events.

Patients with a one standard deviation increase in nighttime systolic BP at baseline had a 38 percent increased risk of reaching this endpoint following multivariate adjustment (hazard ratio [HR] 1.38), while an equivalent increase in nighttime diastolic BP yielded a 36 percent increase in risk (adjusted HR 1.36; P<0.05 for both).

The only significant predictor of death was a so-called “true” diagnosis of resistant hypertension, based on ambulatory BP monitoring rather than office-based measurement. This diagnosis was associated with a twofold increase in the risk of all-cause mortality (adjusted HR 2.00; P<0.05).

Chai estimates that up to a quarter of patients being followed up at the NUHCS have resistant hypertension. He said that he presently uses both forms of BP measurement but noted that not all hypertensive patients require ambulatory BP monitoring.

The results of the study cannot be generalized to all patients with hypertension, he added.