Measurements of SBP at 3 or 5 minutes tend to over-predict the proportion of hypertensive subjects.
While international recommendations suggest 3—5 minutes of rest needed before blood pressure (BP) measurement, a cross-sectional bicentric study determined 25 minutes is the minimal resting time to obtain a stable systolic blood pressure (SBP), according to a study published in Scientific Reports.
About one third of American adults are diagnosed with hypertension, reading 140/90 mmHg or higher, which costs the nation $48.6 billion each year. The American Heart Association (AHA), the European Society of Cardiology (ESC) and the European Society of Hypertension (ESH), among others, proposed recommendations for blood pressure measurement suggesting a resting time varying from 3—5 minutes before BP measurement.
"We think that the resting time before office or ambulatory blood pressure measurement should be considered especially in older people in order to avoid adverse events (fall...) of the hypertensive drug," Guillaume Mahe, professor of vascular medicine, Centre Hospitalier Univeritaire de Rennes, told Md Magazine. "This questions whether the diagnosis of hypertension can be reliably made during routine visits in general practitioners’ offices."
A cross-sectional, observational study, performed in France, studied 199 outpatients 18 years of age addressed to a vascular examination — either a carotid ultrasound exam, suspected peripheral artery disease, suspected venous disease or a cardiovascular prevention visit. Only those patients whose arm pressure could be measured in both arms were included.
101 subjects (51%) SBP and diastolic BPs (DBP) were studied in the reclining position, while 98 subjects (49%) were studied in a seated position. BP was followed on the left arm in 106 subjects (53%), and 93 subjects (47%) on the right arm. It was measured using 2 automatic monitors every minute during 11 consecutive minutes.
Stimulations showed that only 50% of the population was stabilized within 5 mmHg of systolic pressure after 5 minutes of resting time and that measurements of SBP at 3 or 5 minutes tend to over predict the proportion of hypertensive subjects.
The predicted proportion of subjects diagnosed as hypertensive dropped from 50% when averaging measurements at 3 and 5 minutes to 44%, while resting for 25—27 minutes would bring the rate down to 33%.
"We show that following AHA or ESC recommendations in subjects adressed in a vascular unit increases the prevalence of hypertension as compared to the use of our minimal resting time of 25 minutes," Mahe noted.
The study showed that among outpatients addressed for a vascular examination, the minimal resting time before blood pressure measurement to obtain a stable SBP in 90% of the population, is 25. The results suggest that 5 minutes are not enough to achieve a stabilized SBP in most patients and at least 25 minutes are required.
The resting time found is far longer than the resting time proposed by all previous scientific statements. According to the study results, the leading guidelines about the office measurement of blood pressure may contribute to increase the prevalence of hypertension, subsequently growing the number of patients receiving antihypertensive drugs.
“In our opinion, hypertension diagnosis should be performed in a dedicated place during a specific consultation,” Mahe, said. “At the very least, a suspicion of hypertension in a patient should warrant a second measurement after a longer rest period than the current recommended 5 minutes."
Researchers believe that nearly 700,000 of patients in France may be misdiagnosed for hypertension, and that number could be 5 times higher in the US. Replication of the current study with more subjects from diverse populations is needed.
The study, “A minimal resting time of 25 min is needed before measuring stabilized blood pressure in subjects addressed for vascular investigations,” can be found in Scientific Reports.