Hypertension is a very strong and established risk factor for cardiovascular disease. A timely and accurate diagnosis is therefore crucial for primary prevention of heart disease. However, hypertension remains undiagnosed and undertreated in many because of its insidious nature despite it being amenable to easy diagnosis and treatment.

A new study published in the journal Hypertension says that BP should be measured in both arms and the higher reading should be taken into consideration as being more diagnostic of hypertension.¹

Clark and coauthors studied data of 53,172 adults from 23 international studies from the Inter-arm Blood Pressure Difference-Individual Participant Data Collaboration. These participants had their BP recorded in both arms. Their mean age was 60 years. Women comprised almost half (48%) of the study population. In this study, the researchers sought to examine associations of higher or lower readings of arm systolic BP with the diagnosis of hypertension, cardiovascular events and mortality.

Almost 30% of participants had a systolic inter-arm difference in BP of ≥10 mm Hg, based on a single pair of readings. A mean difference of 6.6 mm Hg was noted in the arm systolic BP between higher and lower readings. When the higher arm reading was used, the systolic BP of 6572 participants (12.4%) was reclassified from below to above 130 mm Hg. And in 6339 (11.9%) patients, it was reclassified from below to above 140 mm Hg.

Among patients with no underlying heart disease, the mean ASCVD scores  and Framingham risk scores to estimate the 10-year risks of cardiovascular events showed a significant rise when the higher systolic BP value was used to calculate the scores compared to the lower BP reading. This led to reclassification of 4.5% and 9.3% of participants with ASCVD and Framingham scores, respectively from below to above clinically important cardiovascular risk thresholds.

Sometimes, the BP reading in both arms may vary. While a difference of a few points is not a cause for concern, a difference of 10-15 mmHg has prognostic significance. In its 2019 scientific statement, the American Heart Association (AHA) recommends that BP should be recorded in both arms at the first visit and to use the arm with the higher reading for measurements at subsequent visits.² But this may not be widely practiced in clinics. While it sounds cumbersome and time-consuming, it will facilitate accurate diagnosis of hypertension and risk stratification for cardiovascular disease. All management decisions should be based on the higher reading. Measuring BP only in one arm may run the risk of the diagnosis of hypertension being missed and also underestimation of their cardiovascular risk.

This study provides strong evidence that using the higher reading of arm BP, instead of the lower reading, reclassifies individuals over the thresholds used to diagnose hypertension and also improves cardiovascular risk stratification. Many would have fallen through the net if the lower reading was considered. Hence, it’s of vital importance that BP is routinely measured in both arms.

 References

1. Paul Muntner, et al. Measurement of blood pressure in humans: a scientific statement from the American Heart Association. Hypertension. 2019 May;73(5):e35-e66. doi: 10.1161/HYP.0000000000000087. https://www.ahajournals.org/doi/10.1161/HYP.0000000000000087
2. Christopher E Clark, et al. Higher arm versus lower arm systolic blood pressure and cardiovascular outcomes: a meta-analysis of individual participant data From the INTERPRESS-IPD Collaboration. Hypertension. 2022 Aug 2;HYPERTENSIONAHA12118921. doi: 10.1161/HYPERTENSIONAHA.121.18921.