Blood pressure. Assessment of interarm differences

Background: Although a large interarm blood pressure difference is assumed to help identify patients with aortic dissection, the degree of normal interarm blood pressure variation has not been well defined. Methods: To determine the normal variation in bilateral upper-extremity blood pressure measurements, we conducted a prospective observational study on a convenience sample of ambulatory patients who were seen at a university hospital emergency department. Bilateral upper-extremity blood pressure measurements were performed with an automated blood pressure monitor at the time the patient was seen. Clinical and demographic data collected included age, sex, race, medical history, chief complaint, cardiac risk factors, pulse, bilateral blood pressure measurements, and discharge diagnosis. The primary outcome measures were the interarm blood pressure differences. Results: Of 610 patients, 324 (53%) had a systolic or a diastolic interarm blood pressure difference of more than 10 mm Hg, and 113 (19%) had a systolic or a diastolic interarm blood pressure difference of more than 20 mm Hg. The variation in interarm blood pressure measurements was unrelated to age, gender, race, mean arterial pressure, cardiovascular risk factors, or discharge diagnosis. The mean interarm systolic blood pressure difference was significantly greater in patients with known coronary artery disease (14.5 vs 10.4 mm Hg; P = .05, Student t test). Conclusion: Bilateral upper-extremity blood pressure determinations, as measured by automated indirect measurement, have a wide degree of interarm variation.