Blood pressure, as measured in a medical office, does not seem to predict future heart risks, in comparison with continuous blood pressure monitoring in individuals with treatment-resistant hypertension, according to an article released on November 24, 2008 in Archives of Internal Medicine, on of the JAMA/Archives journals.
Between 10 and 30% of patients with high blood pressure actually have resistant hypertension, when blood pressure remains high despite administration of at least three antihypertensive drugs, including a diuretic, according to the background information in the article. When managing these patients, it is important to take blood pressure at regular intervals throughout the day to avoid the “white-coat” effect, in which a patient reports a higher blood pressure in the physician’s office.
To investigate the ability of different types of blood pressure measurement on patients with resistant hypertension, Gil F. Salles, M.D., Ph.D., examined 556 patients with resistant hypertension attending an outpatient clinic between 1999 and 2004. The subjects underwent a clinical exam, including a blood pressure measurement, over 24 hours, with recordings every 15 minutes during the day and 30 minutes in the night. Followup was performed three to four times per year until December 2007, with a median followup time of 4.8 years.
Out of the total, 19.6% (109) of the participants experienced a cardiovascular event or death due to cardiovascular disease. These events included 44 strokes, 21 heart attacks, 10 new cases of heart failure, and five sudden deaths. In the study, 12.6% (70) died, 8.3% (46) of the total population dying from cardiovascular disease.
The blood pressure measured in the medical office was not predictive of any of these events. However, ambulatory blood pressure was associated with both fatal and non-fatal heart events. This association persisted even after controlling for office blood pressure and other cardiovascular disease risk factors. Nighttime blood pressure was better for predicting heart events than daytime pressure.
The authors note the importance of this potential finding. “This study has important clinical implications,” they write. “First, it reinforces the importance of ambulatory blood pressure monitoring performance in resistant hypertensive patients. Furthermore, ambulatory blood pressure monitoring should be performed during the whole 24 hours, with separate analyses of the daytime and nighttime periods, because it seems that nighttime blood pressures are better cardiovascular risk factors than are daytime blood pressures.”
“Second, it raises the question of whether therapeutic interventions directed specifically at controlling nighttime hypertension will be able to improve cardiovascular prognosis compared with the traditional approach of controlling daytime blood pressure levels,” they continue. “This important clinical question should be addressed in future prospective interventional studies.”
Prognostic Influence of Office and Ambulatory Blood Pressures in Resistant Hypertension
Gil F. Salles, MD, PhD; Claudia R. L. Cardoso, MD, PhD; Elizabeth S. Muxfeldt, MD, PhD
Arch Intern Med. 2008;168(21):2340-2346.
Written by Anna Sophia McKenney